hotels project design tips

HVAC

DESIGN TIPS FOR HOSPITALITY

PROJECTS.

Compiled by: [email protected]

PROJECT DESIGN :: HOTEL

Goal: To create an aesthetically pleasing and calming environment, which encourages guests to feel

relaxed and comfortable so that they enjoy their stay and are more apt to return. To minimize noise

from other guest rooms, the corridor and mechanical equipment.

• Tips/Considerations

o There are several issues that must be addressed concerning acoustics in a hotel project.

These issues stem from the two types of sound that must be controlled: airborne sound

and impact sound. A typical airborne sound is music or talking. A typical impact sound is

the footfall sound of an upstairs guest.

o There are two rating systems that compare the acoustic quality of various building

assemblies. Both classify acoustical performance with a single number. In both cases, the

higher the number, the better the sound isolation performance. Sound Transmission

Class (STC) rates a partition's resistance to airborne sound transfer.

o The Uniform Building Code (UBC) contains requirements for sound isolation between

dwelling units in Group R occupancy project (including hotels). However, these criteria

are not universally enforced. UBC requires walls and floor/ceiling assemblies to have an

STC rating of 50. The code also requires that floor/ceiling assemblies have an Impact

Insulation Class rating of 50. *NOTE: Even if a particular municipality has not adopted

this part of the code, it is still recognized as an industry standard minimum.

o Resilient channel can be used to help improve the isolation quality of a wall. However, if

artwork and/or headboards are mounted against the wall (as is often the case in a hotel),

the effectiveness will be greatly diminished. Consider increasing the isolation through

some other means (i.e., increased mass, increased air space, double or staggered stud

walls, etc…).

o All air-gaps and penetrations must be carefully controlled and sealed. Even a small air-

gap can degrade the isolation integrity of an assembly.

o The perimeter of the wall and any penetration must be sealed air-tight with a non-

hardening acoustic sealant.

o Avoid the installation of back-to-back penetrations (outlets, light switches, and phone

jacks). Consider installing a putty pad to the back of all outlets in party walls.

o Ideally, elevator shaft footings, floor pads, masonry shaft walls, elevator equipment

mountings, etc. should be totally isolated from the building structure. Structure borne

noise/vibration from elevator operation may be extremely annoying. Additionally, any

penetration or air gap in or around the wall must be sealed airtight with a non-hardening

acoustic sealant.

o The building code (UBC) specifies that the entrance doors from interior corridors shall

have an STC rating of 26 or higher. The higher the STC rating of the doors, the better the

isolation. However, if the seal around and under the door is not maintained, selecting a

high rated door is meaningless. Ideally, drop seals that seal to a threshold (not carpet)

can be installed. An acoustically absorptive ceiling and carpet in the corridor will help to

control the noise levels within the corridor.

o The majority of noise concerns can be alleviated through proper space planning.

Sensitive areas should not be located near potentially noisy areas. Potentially annoying

sound transmission from floor to floor (for example, from a restroom or laundry facility

above a bedroom) can be mitigated through the vertical mirror of spaces. Potentially

noisy areas (such as elevators, vending rooms and laundry facilities) should not be

adjacent to guest rooms.

o Although the building code does not address plumbing noise, this issue can be a major

source of noise complaints. Plumbing noise can be both airborne and structure borne. To

reduce plumbing noise, pipes should be resiliently mounted, that is, adequately insulated

from their supports. To further reduce plumbing noise, the pipes should be wrapped with

pipe lagging material.

o Any roof-mounted equipment should be analyzed for potential noise/vibration impact.

o Consider the exterior noise impact to the guest rooms (such as a nearby airport or

freeway). The majority of this noise is transmitted through the windows and P-Tac units.

Upgrading these elements might be necessary.

Noise Criteria (NC) ratings can be used to specify the allowable background noise levels (not including

activity noise from the occupants) within a given space. Recommended NC levels vary depending on

the type of space and the listening requirements. The recommended NC level for a bedroom is NC

20-30. Most hotel air-conditioning systems produce noise levels well in excess of the

recommendation. Additionally, HVAC noise can act as a masking system in hotel projects, raising the

background noise level and thus reducing the awareness of transmitted noise. (NOTE: Obviously, this

benefit only occurs when the system is on.) The equipment noise should not exceed NC 25-30 and

the air noise of the HVAC system should not exceed NC 35.

Project Design :: Ballroom

Goal: To create a multi-purpose space that can successfully control noise and can provide an

acoustic environment appropriate for meetings and receptions, both large and small.


o Recommended reverberation time: 1-1.2 seconds

o Absorptive materials on the ceiling and/or walls are needed to reduce the reverberation

time.

o Be cautious when designing ceiling intricacies, as they may cause unwanted reflections.

Concave, barrel and peaked elements can cause reflections to be focused, which might

lead to annoying reflections and noise build up.

o Operable walls covered with fabric alone do not guarantee absorption.

o The STC rating of the operable walls only refers to how well an individual panel performs

in a laboratory and does not necessarily indicate how well the system will perform in the

field. Specifying an NIC rating can help ensure the desired isolation level.

o Once divided by operable walls, the acoustics in the new space can change.

o Beware of potential noise impact to your space from exterior sources and/or excessive

HVAC noise. To help protect your design, the NC level should not exceed 30 to 40. When

specifying NC, specify an actual rating, such as NC 35, rather than a range, such as NC

30-35. Although specifying a lower number will ensure minimal background noise, it

might be cost prohibitive to achieve. Be realistic about the amount of acceptable noise

and the project's budget when specifying an NC level.

o Maintain an elegant appearance by addressing acoustical issues during the design phase.

Retrofitting after construction will limit your options, possibly impacting the aesthetic

integrity of the space.

Project Design :: Corridor

Goal: To prevent noise from traveling throughout the corridors and/or hallways.


o If surfaces are left untreated, a corridor can act as a megaphone, transmitting

conversations into nearby spaces.

o Be cautious with curved surfaces, as they can compound this megaphone effect.

o The noise criteria for background noise (HVAC) should not exceed NC 35-40.

Project Design :: Lobby

Goal: To create an aesthetically pleasing and inviting space that does not compromise the

confidentiality or productivity of the rest of the office and does not overwhelm the visitor with

excessive noise.


Due to their high ceilings and reflective surfaces (glass, drywall and no carpet), lobbies can become

reverberant, causing a buildup of noise. Lobbies are often not considered acoustically critical spaces,

and some facilities choose to have an "active buzz" in this type of space. However, if there will be

people within the space (receptionist, security guard, waiting room, etc…), this build up of noise can

become problematic. The installation of acoustically absorptive materials can mitigate this concern.

Project Design :: Meeting Room

Goal: To provide a space where a variety of communication styles can be effectively used.


o Recommended reverberation time is

approximately 1 second.

o Absorptive materials will most likely be necessary

for the ceiling.

o Even if the reverberation time is optimally

controlled, reflections from the walls can be

problematic. Slap back from the back wall can

create an issue for the presenter and parallel

reflective surfaces can cause an annoying condition called flutter echo or standing wave.

Ideally, at least the back wall and one side wall should be treated with acoustically

absorptive material. It might not be necessary to completely treat the wall as long as the

critical zone (normally from 3'-7') is treated with a material that has an NRC of at least

0.50, ideally at least 0.80.

o Draperies typically provide very little, if any, absorption.







o If confidentiality or privacy is an issue, you need to be concerned with the isolation

quality of the wall. Even if you specify a high STC rating for the wall, it will not allow for

privacy if the wall only extends to the ceiling, or just above the ceiling. For optimal

confidentiality, the wall must extend to, and seal to, the deck. Remember, the STC rating

of a wall only refers to how well a section of that wall performs in a laboratory and does

not necessarily indicate how well the system will perform in the field. Specifying an NIC

rating can help ensure the desired isolation level.

o A sound system may be necessary to enhance the presentations.

Project Design :: Restaurant

Goal: To minimize distractions from kitchen noise, outdoor noise and noise from nearby

conversations to create a comfortable and safe environment for diners and employees.


o Because of the size of the space and the materials typically used, a restaurant can

become very reverberant, causing a tremendous build-up of noise. Absorptive materials

are needed to help control this reverberation. Even if the restaurant is carpeted, keep in

mind that carpet is only about 20-35% absorptive. Ceiling and/or wall treatments are

necessary.

o The amount of absorption needed will depend on the type of environment you want to

create. Some restaurants are designed for a live, active, noisy feel, while others are

designed to provide a quite, intimate experience. Be sure to understand your client's

specific expectations.

o Although acoustical wall treatments can help, or might be necessary for some

restaurants, the majority of the noise is often controlled through the ceiling treatment.

Thanks to the large array of available product offerings, you can achieve virtually any

look with ceiling treatments (including metal, wood, plaster, etc…).

o Even if your client is not concerned with the level of noise and/or wants a noisy, active

space, the concern must shift to the safety of the employees. Many restaurants and bars

are currently in violation of OSHA, which at the very least, could result in a fine, if not a

lawsuit.







time.


















Project Design :: Spa

Goal: To create an environment suitable for a spa experience – soothing, peaceful and calm. Doing so

entails minimizing distracting noise from adjacent spaces, from one treatment room to another and

from external noise sources (such as street traffic).

Project Design :: Patio Seating

Goal: To create an environment suitable for dining and conversation, taking into consideration the

impact on the surrounding community and the possibility of exposing diners and employees to loud

external noise sources (such as a nearby road or airport).


o To protect diners from noise generated outside of the seating area, a barrier might be

necessary. However, often times, barriers might not be logistically feasible or effective

enough (depending upon the noise source). If you cannot adequately block exterior

noise, consider masking the noise. Many projects have successfully mitigated the issue

through a sound masking system (sometimes as simple as a water fountain).

o The desired level of noise reduction to the surrounding community will depend upon your

local noise ordinance. Contact your local government for more information, or contact us

at [email protected].

o Depending on the type of restaurant in question, the patio can range from relatively quiet

to boisterous (for example, a bar or nightclub patio). Sometimes it is difficult to protect

nearby residences, hotels and/or businesses once the patio is established. In order to

alleviate potential noise problems, be sure to choose the location of the patio carefully,

keeping in mind the location and proximity of surrounding establishments and buildings.

If the location is already established, you can try to create a barrier such as a wall

enclosure. The barrier will not be effective unless it at least blocks the line of sight.

o Vegetation and landscaping provide very little, if any, noise reduction.

Project Design :: Restaurant

Goal: To minimize distractions from kitchen noise, outdoor noise and noise from nearby

conversations to create a comfortable and safe environment for diners and employees.


o Because of the size of the space and the materials typically used, a restaurant can

become very reverberant, causing a tremendous build-up of noise. Absorptive materials

are needed to help control this reverberation. Even if the restaurant is carpeted, keep in

mind that carpet is only about 20-35% absorptive. Ceiling and/or wall treatments are

necessary.

o The amount of absorption needed will depend on the type of environment you want to

create. Some restaurants are designed for a live, active, noisy feel, while others are

designed to provide a quite, intimate experience. Be sure to understand your client's

specific expectations.

o Although acoustical wall treatments can help, or might be necessary for some

restaurants, the majority of the noise is often controlled through the ceiling treatment.

Thanks to the large array of available product offerings, you can achieve virtually any

look with ceiling treatments (including metal, wood, plaster, etc…).

o Even if your client is not concerned with the level of noise and/or wants a noisy, active

space, the concern must shift to the safety of the employees. Many restaurants and bars

are currently in violation of OSHA, which at the very least, could result in a fine, if not a

lawsuit.







time.


















Project Design :: Spa

Goal: To create an environment suitable for a spa experience – soothing, peaceful and calm. Doing so

entails minimizing distracting noise from adjacent spaces, from one treatment room to another and

from external noise sources (such as street traffic).

Project Design :: Sports Complex

Goal: To design a space in which sports fans can enjoy a game or other sports-related activity

without risking their hearing health and without being distracted from the activity by excessive noise.

• Request assistance in developing a noise code.

Project Design :: Outdoor Stadium

Goal: To ensure the acoustic integrity of the outdoor facility while minimizing the noise impact on

surrounding areas, neighborhoods, communities and businesses.

• Related Codes


Project Design :: Conference Room

Goal: To provide a space where a variety of presentation styles can be effectively used without

excessive distractions.


o Recommended reverberation time is between 0.6 and 1 second.

o Absorptive materials will most likely be necessary for the ceiling. Often times, the

perimeter of the ceiling is absorptive and the area above the conference room table is

kept reflective.

o Even if the reverberation time is optimally controlled, reflections from the walls can be

problematic. Slap back from the back wall can create an issue for the presenter and

parallel reflective surfaces can cause an annoying condition called flutter echo or standing

wave. Ideally, at least the back wall and one side wall should be treated with acoustically

absorptive material. It might not be necessary to completely treat the wall as long as the

critical zone (normally from 3'-7') is treated with a material that has an NRC of at least

0.50, ideally at least 0.80.


o Beware of potential noise impact to your space from

exterior sources and/or excessive HVAC noise. To help

protect your design, the NC level should not exceed 25 to

35. When specifying NC, specify an actual rating, such as

NC 30, rather than a range, such as NC 25-30. Although

specifying a lower number will ensure minimal background

noise, it might be cost prohibitive to achieve. Be realistic about the amount of acceptable

noise and the project's budget when specifying an NC level.

o If an electronic masking system is being used throughout the facility, it is best to avoid

installing speakers in the conference room. If this cannot be avoided, consider at least

turning down the speaker(s) in this space.



privacy if the wall only extends to the ceiling, or just above the ceiling. To help ensure





o A sound system may be necessary to enhance the presentations.

9.04.043 Noise limits—Special downtown accessory entertainment uses in the downtown

hospitality central core or downtown hospitality transition area.

Special downtown accessory entertainment uses shall adhere to the following standards:

A. In the downtown hospitality central core area:

1. No person shall produce or allow to be produced by any machine, animal, device, or

any combination of the same on commercial property, a noise level in excess of the following at any

point outside of the property plane:

Project Design :: Office

Goal: To minimize noise-related distractions and maximize productivity in the workplace.


o Typical reverberation time is between 0.4 and 1 second.

o Absorptive materials will most likely be necessary for the ceiling.


problematic. Parallel reflective surfaces can cause an annoying condition called flutter

echo or standing wave. Ideally, at least two non-parallel walls should be treated with

acoustically absorptive material. It might not be necessary to completely treat the wall as

long as the critical zone (normally from 3'-7') is treated with a material that has an NRC

of at least 0.50, ideally at least 0.80.








o Awareness of activity in adjacent spaces is typical in most offices. However, if the

transmitted speech is intelligible, it becomes far more distracting. Additionally,

confidentiality and speech privacy can become a serious concern. Noise transfer is due to

the isolation quality of a wall assembly, as well as any potential flanking paths. The

isolation quality of an assembly is largely determined by the weakest point of the

assembly. Any air-gap can substantially degrade the isolation quality of the assembly.

Even if the assembly has a high STC rating, a variety of flanking paths can allow noise

transmission and speech to be understood between spaces. Some of the sound paths

that can contribute to potential noise transfer are:

� Wall Assembly

� Door Assembly

� Penetrations (outlets)

� Air-Gap between wall and window mullion

� Flanking over the wall/through the ceiling

� Through the ductwork








o Client Expectations: There is a large range of acceptable isolation levels for office spaces.

Transmitted noise that would be tolerable for some projects can be very annoying for

others. The annoyance potential is based on individual sensitivities, confidentiality issues,

and the level of privacy to which the users are accustomed. It is important to understand

your client's needs in regard to privacy and confidentiality expectations in order to design

a space that is best suited for their individual needs.

Project Design :: Private Office

Goal: To minimize noise-related distractions and maximize productivity in the workplace.


o Typical reverberation time is between 0.4 and 1 second.



problematic. Parallel reflective surfaces can cause an annoying condition called flutter

echo or standing wave. Ideally, at least two non-parallel walls should be treated with

acoustically absorptive material. It might not be necessary to completely treat the wall as

long as the critical zone (normally from 3'-7') is treated with a material that has an NRC

of at least 0.50, ideally at least 0.80.








o Awareness of activity in adjacent spaces is typical in most offices. However, if the

transmitted speech is intelligible, it becomes far more distracting. Additionally,

confidentiality and speech privacy can become a serious concern. Noise transfer is due to

the isolation quality of a wall assembly, as well as any potential flanking paths. The

isolation quality of an assembly is largely determined by the weakest point of the

assembly. Any air-gap can substantially degrade the isolation quality of the assembly.

Even if the assembly has a high STC rating, a variety of flanking paths can allow noise

transmission and speech to be understood between spaces. Some of the sound paths

that can contribute to potential noise transfer are:

� Wall Assembly

� Door Assembly

� Penetrations (outlets)

� Air-Gap between wall and window mullion

� Flanking over the wall/through the ceiling

� Through the ductwork








o Client Expectations: There is a large range of acceptable isolation levels for office spaces.

Transmitted noise that would be tolerable for some projects can be very annoying for

others. The annoyance potential is based on individual sensitivities, confidentiality issues,

and the level of privacy to which the users are accustomed. It is important to understand

your client's needs in regard to privacy and confidentiality expectations in order to design

a space that is best suited for their individual needs.

Project Design :: Open Office

Goal: To provide an environment free from distraction, by reducing noise levels and minimizing

interruptions from nearby conversations.


o Recommended reverberation time is 0.75 seconds.

o Avoid direct sound pathways between cubicles by proper placement of wall partitions.

o Without controlling reflections off the ceiling and perimeter walls, partitions can be

ineffective.

o Absorptive wall partitions, ceiling tile and wall treatments will be necessary to control the

reverberation time.

o Reasonable precautions should be taken to insulate against noise from adjacent rooms,

machinery, ducts and external noise sources.

o It's almost impossible to achieve speech privacy in an open office environment without

installing an electronic masking system.

o For more information on masking systems, read Creating the Ideal Workspace: Sound

Masking Systems which includes a checklist of considerations.

o Also visit the ASTM Standard Guide for Open Office Acoustics (ASTM

E1374-02).

Project Design :: Breakroom/Common Area

Goal: To absorb excessive noise from employees conversing, televisions, snack machines, etc… while

ensuring noise within this space does not distract employees working nearby.


o Many noise control issues can be alleviated through proper space planning. Avoid

placing potentially noisy spaces, such as break rooms, close to critical areas.

o Consider using an absorptive ceiling system in this type of space to help control

reflections and the build up of noise.

Project Design :: Outdoor Stadium

Goal: To ensure the acoustic integrity of the outdoor facility while minimizing the noise impact on

surrounding areas, neighborhoods, communities and businesses.

• Related Codes


Project Design :: Conference Room

Goal: To provide a space where a variety of presentation styles can be effectively used without

excessive distractions.

Project Design :: Cafeteria

Goal: To minimize the noise levels in an environment known for excessive noise. To control the

impact of noise generated in the cafeteria to surrounding spaces.


o Because of the size and the materials typically used in this type of space, a cafeteria

can become very reverberant, causing a tremendous build up of noise. Absorptive

materials are needed to help control this reverberation. Typically, you wouldn't carpet

a cafeteria; even if you did, carpet is only about 20-35% absorptive. Ceiling and/or

wall treatments are necessary.

o If occupants can come in contact with the wall, use materials that are cleanable and

durable. This is less of a concern if the wall treatment is out of reach.

o Keep in mind that cafeterias are often used as multi-purpose rooms, and/or

gymnasiums.

Project Design :: Counseling Office

Goal: To create a comfortable environment and to minimize the risk of overhearing conversations in

adjacent rooms, ensuring patient privacy.


o Recommended reverberation time is between 0.6 and 1 second.


o Even if the reverberation time is optimally controlled, problematic reflections from the

walls can be an issue. Parallel reflective surfaces can cause an annoying condition

called flutter echo or standing wave. Ideally, at least two non-parallel walls can be

treated with acoustically absorptive material. It might not be necessary to completely

treat the wall as long as the critical zone (normally from 3'-7') is treated with a

material that has an NRC of at least 0.50, ideally at least 0.80.


o Beware of potential noise impact to your space from exterior sources and/or

excessive HVAC noise. To help protect your design, the NC level should not exceed

25 to 35. When specifying NC, specify an actual rating, such as NC 30, rather than a

range, such as NC 25-30. Although specifying a lower number will ensure minimal

background noise, it might be cost prohibitive to achieve. Be realistic about the

amount of acceptable noise and the project's budget when specifying an NC level.


quality of the wall. Even if you specify a high STC rating for the wall, it will not allow

for privacy if the wall only extends to the ceiling, or just above the ceiling. For

confidentiality, the wall must extend to, and seal to, the deck. The STC rating of a

wall only refers to how well a section of that wall performs in a laboratory and does

not necessarily indicate how well the system will perform in the field. Specifying an

NIC rating can help ensure the desired isolation level.

Project Design :: Lobby

Goal: To create an aesthetically pleasing and inviting space that does not compromise the

confidentiality or productivity of the rest of the office and does not overwhelm the visitor with

excessive noise.


o Due to their high ceilings and reflective surfaces (glass, drywall and no carpet),

lobbies can become reverberant, causing a buildup of noise. Lobbies are often not

considered acoustically critical spaces, and some facilities choose to have an "active

buzz" in this type of space. However, if there will be people within the space

(receptionist, security guard, waiting room, etc…), this build up of noise can become

problematic. The installation of acoustically absorptive materials can mitigate this

concern.

Project Design :: Cafetorium

Goal: To create an environment suitable for use as a cafeteria and an auditorium, while accounting

for the acoustic needs of both.


o Because of the size and the materials typically used in this type of space, a cafeteria

can become very reverberant, causing a tremendous build up of noise. Absorptive

materials are needed to help control this reverberation. Typically, you wouldn't carpet

a cafeteria; even if you did, carpet is only about 20-35% absorptive. Ceiling and/or

wall treatments are necessary.

o If occupants can come in contact with the wall treatment, use materials that are

cleanable and durable. This is less of a concern if the wall treatment is out of reach.

o It is vital to control the reflections from the back wall. If you don't control them, the

presentation could reflect off the back wall and "slap back" to the presenter(s). This

won't necessarily impact the audience, but could be disastrous and distracting for the

people on stage. Because of this, it's usually necessary to treat the back wall with an

absorptive material.

o HVAC noise, which is often overlooked, can negatively impact the usability of a

space. To help protect your design, the NC level should not exceed 30 to 35. When

specifying NC, specify an actual rating, such as NC 30, rather than a range, such as

NC 30-35. Although specifying a lower number will ensure minimal background noise,

it might be cost prohibitive to achieve. Be realistic about the amount of acceptable

noise and the project's budget when specifying an NC level.

Project Design :: Gymnasium

Goal: To properly absorb excessive noise in this naturally loud environment to protect the users and

minimize distractions and help to ensure the audibility of the PA system.


o Because of the size and the materials typically used in this type of space, a

gymnasium can become very reverberant, causing a tremendous build up of noise

and difficultly understanding the PA system. Absorptive materials are needed to help

control this reverberation. Ceiling and/or wall treatments are necessary. If the space

is also used for assemblies, meetings or other activities, reducing the reverberation

time is even more critical. The reverberation time needs to be below 2 seconds if you

are just concerned with gymnasium noise, but in order to facilitate other activities, a

reverberation time of 1-1.5 seconds is ideal. A reverberation time of above 2 seconds

is unacceptable.

o Given the activities taking place in a gymnasium, and the equipment used for these

activities, durability is a critical factor when choosing acoustic materials.

o Even if everything else is controlled perfectly, the space might be negatively

impacted if the background noise (e.g. HVAC system) is too loud. To help protect

your design, the NC level should not exceed 35 to 45 (when used only as a

gymnasium), 35 to 40 (when used only as a multipurpose room). When specifying

NC, specify an actual rating, such as NC 20, rather than a range, such as NC 20-30.

Although specifying a lower number will ensure minimal background noise, it might

be cost prohibitive to achieve. Be realistic about the amount of acceptable noise and

the project's budget when specifying an NC level.

o Noise from the gym could potentially impact the surrounding spaces. Try not to

locate quiet spaces (such as a library, or classroom) next to a gymnasium. If this

can't be avoided, it is critical to ensure a high STC rating.

Project Design :: Multi-purpose Room

Goal: To provide a space acoustically suitable for a variety of uses.


o Because of the size and the materials typically used in this type of space, a multi-

purpose room can become very reverberant. This can cause a tremendous build-up

of noise. To help control this reverberation, absorptive materials are needed.

Although carpeting might help, it is not a cure-all, as it is only about 20-35%

absorptive. Ceiling and/or wall treatments will probably be necessary.



35 to 40, unless it is used frequently for performances (in this case, the range should

be 30-35). When specifying NC, specify an actual rating, such as NC 35, rather than a




o Sometimes multi-purpose rooms are used for performances or presentations. If this is

the case, you should consider acoustically treating the back wall (the wall opposite

the stage or performance area). It is important to control the reflections from the

back wall. If you don't control them, the presentation could reflect off the back wall

and "slap back" to the presenter(s). This won't necessarily impact the audience, but

could be disastrous and distracting for the people on stage. A concave back wall

could compound this problem. If you can't avoid a concave back wall, it's imperative

that it be treated with absorptive material.

Project Design :: Library

Goal: To limit noise levels, allowing users to read and contemplate without distractions.


o Recommended reverberation time is 0.8 to 1 second.

o Absorptive materials are needed to reduce the reverberation time.

o If domes or other concave surfaces are desired, they must be treated with absorptive

materials to reduce unwanted reflections.






and the project's budget when specifying an NC level. NC is not a consideration for an

outdoor space.

o The majority of noise concerns can be alleviated through proper space planning. If

possible, place noisy equipment and activities in remote areas.

Project Design :: Auditorium/Theater

Goal: To properly balance absorption and reflection to

provide a favorable acoustical environment. One must

address both the need to hear and understand speech, and

the desire to have a pleasant space for music.


o Recommended reverberation time is 1.0-1.5 seconds (might be higher for some

auditoriums).

o Although the seating area will provide absorption, thereby reducing the reverberation

time, you will most likely need to add absorptive materials to the other surfaces within

the space.





absorptive material. A concave back wall could compound this problem. If you can't avoid

a concave back wall, it's imperative that it be treated with absorptive material.

o Splay or use irregular surfaces on the walls to avoid flutter echoes. Parallel reflective

surfaces can allow sound to "ricochet" back and forth between the surfaces. This

potentially annoying condition is referred to as standing wave or flutter echo. It is

avoided by constructing non-parallel surfaces or by adding absorptive materials to the

surface(s).

o Consider faceting the ceiling to help with sound dispersion.

o Control the reverberation time on the stage. Ideally, the reverberation time in the stage

area should be the same as in the house. Since the stage area might have a higher

ceiling than the rest of the auditorium, more absorptive materials might be required in

this area. Frequently, the back wall of the stage, and possibly one or two of the side

walls, is treated with an acoustically absorptive material, typically black in color.

o Remember the space will be less absorptive when only half full, since the audience itself

is absorptive. By using absorptive seating areas, the reverberation time will remain more

consistent regardless of the audience size.

o Noise from the lobby area can be disruptive. Be sure openings such as doorways are

properly sealed. Consider a vestibule door system.

o Persons seated deep under a balcony might experience auditory distortion. To avoid this,

the balcony should be no deeper than twice its height. Ideally, the balcony should not be

any deeper than its height.

o Even if everything else is controlled perfectly, the space might not be usable if the

background noise (e.g. HVAC system) is too loud. To help protect your design, the NC

level should not exceed 20 to 35. When specifying NC, specify an actual rating, such as

NC 20, rather than a range, such as NC 20-30. Although specifying a lower number will

ensure minimal background noise, it might be cost prohibitive to achieve. Be realistic

about the amount of acceptable noise and the project's budget when specifying an NC

level.

o Beware of potential outdoor noise impacting your space. For example, is your location

near a flight path, a railroad or freeway? If so, you might have to pay critical attention to

blocking this noise. To do so effectively, you must address not only the STC or isolation

quality of the exterior wall, but also for the possibly weaker building elements, such as

the windows, doors and HVAC systems.

Project Design :: Theater

Goal: To properly balance absorption and reflection to provide a favorable acoustical environment.

To address both the need to hear and understand speech, and to enhance musical performances, if

applicable.


o Recommended reverberation time is 1.0-1.3 seconds (might be higher for some theaters,

particularly for music performances).

o Although the seating area will provide absorption, thereby reducing the reverberation

time, you will most likely need to add absorptive materials to the other surfaces within

the space.

o Control the reverberation time on the stage. Ideally, the reverberation time in the stage

area should be the same as in the house. Since the stage area might have a higher

ceiling than the rest of the theater, more absorptive materials might be required in this

area. Frequently, the back wall of the stage, and possibly one or both of the side walls, is

treated with an acoustically absorptive material, typically black in color.





absorptive material. A concave back wall could compound this problem. If you can't avoid

a concave back wall, it's imperative that it be treated with absorptive material.

o If there is a balcony, consider adding an acoustic treatment to its face to avoid slap back.

o Splay or use irregular surfaces on the walls to avoid flutter echoes. Parallel reflective

surfaces can allow sound to "ricochet" back and forth between the surfaces. This

potentially annoying condition is referred to as standing wave or flutter echo. It is

avoided by constructing non-parallel surfaces or by adding absorptive materials to the

surface(s).

o Consider faceting the ceiling to help with sound dispersion.

o Remember the space will be less absorptive when only half full, since the audience itself

is absorptive. By using absorptive seating areas, the reverberation time will remain more

consistent regardless of the audience size.

o Noise from the lobby area can be disruptive. Be sure openings such as doorways are

properly sealed. Consider a vestibule door system.

o Persons seated deep under a balcony might experience auditory distortion. To avoid this,

the balcony should be no deeper than twice its height. Ideally, the balcony should not be

any deeper than its height.







level.

o Beware of potential outdoor noise impacting your space. For example, is your location

near a flight path, a railroad or freeway? If so, you might have to pay critical attention to

blocking this noise. To do so effectively, you must address not only the STC or isolation

quality of the exterior wall, but also for the possibly weaker building elements, such as

the windows, doors and HVAC systems.

Project Design :: Clubhouse/Common Area

Goal: To create a space suitable for social and professional gatherings and/or workout areas without

compromising the acoustic environments of that space or of the surrounding areas.


o Because of the size and the materials typically used in this type of space, a clubhouse

can become very reverberant. This can cause a tremendous build up of noise. To

help control this reverberation, absorptive materials are needed. Although carpeting

might help, it is not a cure-all, as it is only about 20-35% absorptive. Ceiling and/or

wall treatments will probably be necessary.



35 to 40, unless it is used frequently for performances (in this case, the range should

be 30-35). When specifying NC, specify an actual rating, such as NC 35, rather than a




o Sometimes clubhouses are used for performances or presentations. If this is the

case, you should consider acoustically treating the back wall (the wall opposite the

stage or performance area). It is vital to control the reflections from the back wall. If

you don't control them, the presentation could reflect off the back wall and "slap

back" to the presenter(s). This won't necessarily impact the audience, but could be

disastrous and distracting for the people on stage. Because of this, it's usually

necessary to treat the back wall with an absorptive material. A concave back wall

could compound this problem. If you can't avoid a concave back wall, it's imperative

that it be treated with absorptive material.

Project Design :: Classroom

Goal: To limit noise levels, allowing students and teachers to enjoy an optimal acoustic environment

that is conducive to focusing, interacting and general learning.


o Recommended reverberation time is 0.4-1.0 seconds (depending on the size of the

space).

o Numerous studies demonstrate how chronic noise exposure (i.e., noise found in the

community, as well as noise to which we are voluntarily exposed) negatively impacts

education. For more information, read Progressing the Learning Curve.

o Noise from air-conditioning/heating units or other equipment on the premises can impact

the educational environment. In addition to an NC specification for inside the classroom,

specify a maximum dB level for all equipment in and around the school.

o Consider the impact of noise from nearby freeways, busy roads, train tracks and other

transportation- or industrial-related sources. Identify noise sources in the vicinity and

assess the possible impact. Based on this assessment, take the proper steps to minimize

or eliminate the potential problem.

o o Noise from adjacent classrooms can be easily transmitted into other classrooms,

particularly in an open-classroom setting. It is vital to control the noise transfer between

spaces. Keep in mind that STC ratings only address noise isolation from 125 Hz to 4000

Hz. Low frequency sounds (below 125 Hz) are not accounted for in an STC rating. Even if

you specify a high STC rating for the wall, it will not allow for privacy if the wall only

extends to the ceiling, or just above the ceiling. To ensure isolation, the wall must extend

to, and seal to, the deck.







level.

Maximum Noise

Level (dBA) Sunday—Wednesday (Hours) Thursday—Saturday (Hours)

74 8:00 a.m.—10:00 p.m. 8:00 a.m.—11:00 p.m.

70 10:00 p.m.—8:00 a.m. 11:00 p.m.—8:00 a.m.

2. No person shall produce or allow to be produced on commercial property a noise by

any machine, animal, device, or any combination of the same on commercial property in excess of

the following noise level as measured at the property plane of the nearest residential zoning district:

Maximum Noise Level (dBA) All Days (Hours)

60 10:00 p.m.—6:00 a.m.

B. In the downtown hospitality transition area:

1. No person shall produce or allow to be produced by any machine, animal, device, or

any combination of the same a noise level in excess of the following at any point outside of the

property plane:


70 8:00 a.m.—9:00 p.m.

60 9:00 p.m.—8:00 a.m.

2. No person shall produce or allow to be produced on commercial property a noise by

any machine, animal, device, or any combination of the same on commercial property in excess of

the following noise level as measured at the property plane of the nearest residential zoning district:


60 10:00 p.m.—6:00 a.m.

3. In the case of a business establishment which: (a) serves alcohol, and (b) is open for

business between the hours of 9:00 p.m. and 8:00 a.m., the business owner and/or agent in charge

shall arrange for responsible agents to patrol the parking lot and take reasonable actions necessary to

inhibit loitering, shouting, fighting, revving of vehicle engines, the rapid acceleration of vehicles and

other activities which would disturb the peace of a residential neighborhood.

4. No trash shall be dumped outside of the enclosed building area between the hours of

9:00 p.m. and 8:00 a.m. In the alternative, a business which finds it necessary or convenient to dump

trash between 9:00 p.m. and 8:00 a.m. may demonstrate pursuant to Section 9.04.110 of this

chapter that sound levels from dumping trash are insignificant or have been adequately mitigated.

This subsection does not prohibit regularly scheduled pick up of trash by commercial garbage

companies.

5. The person in charge of a business premises, whether that person is an owner,

employee, agent or contractor, shall be responsible to assure compliance with subsections (B)(1)

through (4) of this section.

6. The owner of each business subject to this section shall be responsible to inform his

or her managers, employees, agents and contractors of the requirements of this section. (Ord. 2055 §

2, 2012)

Codes & Testing :: Sound Transmission Class (STC)

Code: STC rates a partition's or material's ability to block airborne sound.

Enforcement: Appendix Chapter 35 of the ’88 and ’91 UBC, Appendix Chapter 12, Division II of the

’94 and ’97 UBC will be contained in the forthcoming IBC. Although not all municipalities have

adopted this appendix chapter, it is still recognized as an industry standard.

General Information: The Uniform Building Code (UBC) contains requirements for sound isolation

for dwelling units in Group-R occupancies (including hotels, motels, apartments, condominiums,

monasteries and convents).

UBC requirements for walls: STC rating of 50 (if tested in a laboratory) or 45 (if tested in the field*).

UBC requirements for floor/ceiling assemblies: STC ratings of 50 (if tested in a laboratory) or 45 (if

tested in the field*).

* The field test evaluates the dwelling’s actual construction and includes all sound paths.

Definitions:

• Sound Transmission Class rates a partition’s resistance to airborne sound transfer at the

speech frequencies (125-4000 Hz). The higher the number, the better the isolation.

STC Strength: Classifies an assembly’s resistance to airborne sound transmission in a single

number.

STC Weakness: This rating only assesses isolation in the speech frequencies and provides no

evaluation of the barrier’s ability to block low frequency noise, such as the bass in music or the noise

of some mechanical equipment.

Recommended Isolation Level

An assembly rated at STC 50 will satisfy the building code requirement, however, residents could still

be subject to awareness, if not understanding, of loud speech. It is typically argued that luxury

accommodations require a more stringent design goal (as much as 10dB better – STC 60). Regardless

of what STC is selected, all air-gaps and penetrations must be carefully controlled and sealed. Even a

small air-gap can degrade the isolation integrity of an assembly.

This code is often used in conjunction with Impact Insulation Class (IIC).

For more information on Sound Transmission Class, visit STCratings.com.

Codes & Testing :: Universal Building Code/International Building Code

Code: UBC/IBC - If you are subject to a different building code, please contact us for more

information.

Enforcement: By city, county or state

General Information: The only acoustic or noise requirement listed in the current UBC/IBC code is

the STC/IIC stipulation for Group-R occupancies. It appears that the IBC will soon replace the UBC.

Codes & Testing :: Noise Criteria (NC)

Code: This industry standard (also an ANSI standard) usually pertains to HVAC or mechanical noise

impact.

Enforcement: This standard is often required for certain certifications (such as government medical

facilities) or included in client specifications/standards (for example, some companies have NC

standards that their buildings must meet).

General Information: An NC level is a standard that describes the relative loudness of a space,

examining a range of frequencies (rather than simply recording the decibel level). This level illustrates

the extent to which noise interferes with speech intelligibility. NC should be considered for any project

where excessive noise would be irritating to the users, especially where speech intelligibility is

important. There are a few spaces where speech intelligibility is absolutely crucial, including:

• Recording studios

• Lecture halls

• Performance halls

• Courtrooms

• Libraries

• Worship centers

• Educational facilities

For some areas, such as machine shops or kitchens, it is not essential to maintain a particularly low

NC level.

NC Level Strength: It is important for design professionals to specify NC ratings to protect their

designs (within reason – specifying an acceptable NC level does not have to be a burden on the

budget). Doing so speaks to your reputation as a responsible architect or designer and limits your

liability.

NC Level Weakness: NC does not account for sound at very low frequencies. In spite of numerous

efforts to establish a widely accepted, useful, single-number rating method for evaluating noise in a

structure, a variety of techniques exist today. The vast majority of acoustic professionals use the NC

standard, but it is still important to be aware of the other acceptable methods that do account for low

frequency levels, including (but not limited to):

• Room Criteria (RC) measures background sound in a building over the frequency range 16 Hz

to 4000 Hz. This rating system requires two steps: determining the mid-frequency average

level and determining the perceived balance between high and low frequency sound. To view

the recommended ANSI levels for room criteria for various activity areas, click here.

• Balanced Noise Criteria (NCB) is based on the ANSI threshold of audibility for pure-tones and

is defined as the range of audibility for continuous sound in a specified field from 16 Hz to

8000 Hz.

Recommended ANSI Levels

Codes & Testing :: Reverberation Time (RT60)

Test: RT60 measures the reverberance within a room.

Related Code: RT60 is soon to be adopted under ADA for classroom acoustic criteria.

General Information: Reverberation Time is the time required, in seconds, for the average sound

pressure level in a room to decrease 60 decibels after a source stops generating sound. This test is

standard on certain projects, such as "THX" movie theaters and various government buildings.

Normally, in the design phase, you must demonstrate (through calculations) that a space will achieve

the stipulated reverberation time. Often times, measurements are required to verify results.

Strength: Because RT60 is void of variables, unlike many other tests, it is straightforward and clear-

cut.

Weakness: RT60 does not account for problematic and potentially annoying reflections. Often times,

there is still a need for expert analysis.

Codes & Testing :: Noise Isolation Class (NIC)

Test: NIC is a method for rating a partition's ability to block airborne noise transfer.

Related Code: UBC/IBC and STC

General Information: Similar to a field STC test, NIC is often specified on certain projects (such as

spaces with operable walls, hotels, education facilities). For a field STC test, the individual

transmission loss measurements are modified based on the reverberation time, the size of the room

and the size of the test partition. The NIC does not include these modifications and simply measures

the Transmission Loss between 125 and 4,000Hz.

Strength: Tests the isolation performance of the assembly in the field. It is good to include an NIC

performance requirement within your spec for operable and demountable walls.

Weakness: The NIC rating is highly dependent on the field conditions of the tested space. Because

of this, the tested rating might not be achieved in other spaces or projects.

Codes & Testing :: Noise Reduction Coefficient (NRC)

Standard: NRC is a laboratory rating of a material's sound absorption quality. (Click here to view the

NRC of various common building materials.)

Enforcement: This is more of an industry standard and not necessarily enforced.

General Information: The NRC rating is an average of how absorptive a material is at only four

frequencies (250, 500, 1000 and 2000 Hz). This industry standard ranges from zero (perfectly

reflective) to 1* (perfectly absorptive). It is always expressed as a decimal rounded to the nearest

.05.

*(Based on the testing methodology, and depending upon the material’s shape or surface area, some

products can test at an NRC above 1.)

Strength: This standard is widely used and accepted.

Weakness:

• The NRC rating is only measured at 250, 500, 1000 and 2000 Hz. This is perfectly acceptable

for speech, but can be inadequate for music (and other low-frequency sounds).

• Because this rating is an average, two materials with the same rating might not perform the

same.

• Communication of product ratings by manufacturers can be misleading and sometimes

deceitful for the following reasons:

o The information provided is based on lab tests. Because the lab is a perfect

environment that is rarely duplicated in everyday applications, some products will not

test the same in the field. Certain factors, such as installation variables, are not

accounted for in the lab.

o Some manufacturers will quote absorption at the more-desirable higher frequencies

without clearly explaining the testing conditions. NRC is based only on absorptive

characteristics at the following frequencies: 250, 500, 1000, 2000 Hz. Make sure the

product data you’re reviewing is of these frequencies.

o Make sure the mounting procedure used in the tests is consistent with your intended

installation if you expect the same results. For example, a manufacturer of a wall

carpet product provides an NRC rating of .80, which is extremely good. But, if you

know how to read the fine print, you’ll see this rating was achieved while the carpet

was installed over fiberglass. In this installation configuration, the fiberglass, not the

carpet, acts as the sound absorber. Without the acoustic material behind, the wall

carpet will probably only achieve an NRC of .20.

A responsible design professional will not rely solely on information provided by manufacturers. While

some do provide accurate information, it is advisable to seek an un-biased third-party for product

confirmation. Visit the Products & Materials section or contact us if you are looking for a specific

product not currently listed in our database.

• Request assistance in developing a noise code.

Recommended ANSI Levels

Occupancy NCB Curve

Broadcast Studios (distant microphone pickup used) 10

Concert halls, opera houses, and recital halls (listening to faint

musical sounds)

10-15

Large auditoriums, large drama theatres, and large churches (for

very good speech articulation)

15-20

TV and broadcast studios (close microphone pickup only) 15-25

Private Residences:

Bedrooms 25-30

Apartments 28-38

Family rooms and living rooms 28-38

Schools:

Lecture and classrooms 25-30

Open-plan classrooms 33-37

Hotels/Motels:

Individual rooms or suites 28-33

Meeting/banquet rooms 25-35

Halls, corridors, lobbies 38-43

Service support areas 38-48

Office Buildings:

Executive offices 25-30

Conference rooms (large) 25-30

Conference rooms (small) and private offices 30-35

General secretarial areas 38-43

Open-plan areas 35-40

Business machines/computers 38-43

Public circulation 38-48

Hospitals and clinics:

Private rooms 25-30

Wards 30-35

Operating rooms 25-30

Laboratories 33-43

Corridors 33-43

Public areas 38-43

Small auditoriums 25-30

Movie theatres 27-37

Churches 30-35

Courtrooms 33-37

Libraries 33-37

Restaurants 38-43

Light maintenance shops, industrial plant control rooms, kitchens,

and laundries

43-53

Shops, garages 50-60

Recommended ANSI Levels for Room Criteria

Occupancy RC Curve

Private Residences 25-30 (N)

Apartments 30-35 (N)

Hotels/Motels

Individual rooms or suites 30-35 (N)

Meeting/banquet rooms 30-35 (N)

Halls, corridors, lobbies 35-40 (N)

Service/support areas 40-45 (N)

Offices

Executive 25-30 (N)

Conference rooms 25-30 (N)

Private 30-35 (N)

Open-plan areas 35-40 (N)

Business machines/computers 40-45 (N)

Public circulations 40-45 (N)

Hospitals and Clinics

Private rooms 25-30 (N)

Wards 30-35 (N)

Operating rooms 25-30 (N)

Laboratories 35-40 (N)

Corridors 30-35 (N)

Public areas 35-40 (N)

Churches 30-35 (N)

Schools

Lecture and classrooms 25-30 (N)

Open-plan classrooms 35-40 (N)

Libraries 35-40 (N)

Courtrooms 35-40 (N)

Legitimate theaters 20-25 (N)

Movie theaters 30-35 (N)

Restaurants 40-45 (N)

Concert and recital halls 15-20 (N)

Recording studios 15-20 (N)

TV studios 20-25 (N)

Codes & Testing :: Outdoor Noise Codes/Ordinances

Code: Numerous municipalities and other agencies' codes stipulate noise level limits.

Enforcement: By city, county or state

General Information: Noise codes are usually measured in decibels and vary from city to city. Most

projects must adhere to a certain noise level, depending on codes applicable to that geographic area.

Some levels are described as specific decibels; others are measured by the ambient noise, which can

be very vague and subjective.

Contact us to:

• Learn more about your city’s outdoor noise code.

• Learn about testing options.

Related Codes & Standards

o ASTM E1374-02: Standard Guide for Open Office Acoustics

o Reverberation Time (RT 60)

o Impact Insulation Class (IIC)

o Universal Building Code/International Building Code (UBC/IBC)

o Noise Isolation Class (NIC)

o Noise Criteria (NC)

o Noise Reduction Coefficient (NRC)

o U.S. Occupational Safety & Health Administration (OSHA)

o Sound Transmission Class (STC)

o Acoustical Performance Criteria, Design Requirements and Guidelines for Schools

Related Projects

• Auditorium/Theater

• Ballroom

• Breakroom/Common Area

• Cafeteria

• Cafetorium

• Cinema

• Concert Venue

• Conference Room

• Corridor

• Classroom

• Clubhouse/Common Area

• Counseling Office

• Entertainment Venue

• Gymnasium

• Healthcare Facility

• Home Theater

• Hotel

• Lecture Hall

• Library

• Lobby

• Meeting Room

• Multi-family housing

• Multi-purpose Room

• Office

• Open Office

• Outdoor Stadium

• Private Office

• Sports Complex

• Patio Seating

• Restaurant

• Spa

• Sports Complex

• Theater

• Worship Center

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sound isolation performance

footfall sound

types of sound

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typical airborne sound

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airborne sound transfer

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