a way to reduce traffic noise pollution

A way to reduce traffic noise pollution

INTRODUCTION OF SOUND

What is Sound?

Sound comes from the vibrations in molecules, and is always traveling through a substance,

whether it is a solid, liquid, or gas. Sound cannot travel through a vacuum because there are

no molecules for the sound to travel through.

When sound waves reach our ears, they vibrate the eardrum. The vibrations are sent through

the three bones in the middle ear. These impulses are then sent to the brain. Our ears are

never free from sound. There is always sound, and some of it is pleasant, and some of it

isnít. If your eyes were as sensitive as your ears, you could see a 100-watt light bulb 3218

kilometers (2000 miles) away. It is hard to find silence, except in soundproof rooms, which

arenít always totally soundproof. There is constant background sound, which we usually

donít notice, and an occasional sudden sound. The background sound can be very helpful to

tell us where we are and what time it is. Sound can also provide other information, and can

serve as a warning system.

If a sound is made, and nobody is around to hear it, it is called unheard sound. If a sound is

made and if there is someone around to hear it, it is called heard sound.

Characteristics of Sound

Sound waves are a series of compressions and rarefactions. Compression occurs when the

molecules are compressed. Rarefaction happens when the molecules are thinned out.

Between the compression and rarefaction zones, there is a neutral zone where the density of

the molecules is equal to or almost equal to the density before the sound was made. These

three zones of high pressure, low pressure, and neutral pressure form a sphere of waves with

the source of the sound at the center.

The wavelength of a sound is the distance from a compression or rarefaction zone to the next

similar area. The amplitude is the pressure difference between compression or rarefaction

zone and the neutral zone. The term amplitude, intensity, and volume are the same, and can be

used to describe loud and quiet sounds.

[email protected] Traffic Engineering - UTM

mailto:[email protected]


Frequency is how many sound waves pass by per second (cycles per second). The number of

cycles per second (or cps) is called hertz. A higher frequency equals a shorter wavelength,

and a lower frequency equals a longer wavelength. Examples of higher frequency sounds are

someone whistling, a flute, and a high voice. Some low frequency sounds include a foghorn,

low voice and the rumble of an earthquake. Everything has a natural frequency. Humans can

hear between 15 Hz and 20,000 Hz. If a sound is above 20,000Hz, it is called an ultrasonic

sound.

Sound travels at different speeds, depending on the substance it is traveling though. The

following chart shows some examples:

SUBSTANCE SPEED

Dry Air/ 0 Degrees C 330 mps

Dry Air/ 1000 Degrees C 700 mps

Hydrogen 1315 mps

Carbon Dioxide 182 mps

Water 1400 mps

Copper 3560 mps

Aluminum 5100 mps

Brass 3505 mps

Granite 3947 mps

Steel 5090 mps

mps = meters per second

An echo is the reflection of sound off of an object. Sonar uses echoes to determine depth, and

other distances. A megaphone also uses reflection to direct beam of sound out of its cone.

Free vibration is vibration that dies out in time such as when a tuning fork is struck.

Maintained vibration is making the vibration last. A trumpet holding a note is an example of

maintained vibration. Forced vibration is making something vibrate at an unnatural

frequency. The eardrum has a natural frequency, too, but is made to vibrate at the frequency

of sounds it receives. The stick and slip vibration method is when something is pulled or




pushed until it slips such as with a violin. The strings of the violin are pulled by the bow until

they slip, creating a vibration. Resonance is sound waves making a separate object vibrate.

Decibels

Sound is measured in decibels (dB). This is a unit measuring the relative intensity of sounds.

The decibel is named after inventor Alexander Graham Bell. Most people speak in a range

between 45 and 75 decibels. A decibel, which is a tenth of a bell, is the smallest change in

sound that a human can hear. The scale starts at 0, which is the quietest sound that can be

heard by a human.

Because sound is measured on a logarithmic scale, an increase of 10 dBA sounds twice as

loud. For example, 30 dBA sounds twice as loud as 20 dBA. A double in the source of a

sound equals a 3 dBA increase. For example, one car may have a 70 dBA sound level. Two

cars at the same speed, distance, and point would then have a 73 dBA sound level, and 4 cars

at the same speed, distance, and point would have a 76 dBA sound level.

The amplitude of a sound increases as you get closer to the source of a sound, and decreases

as you move away. The change in intensity is related to the square of the ratio of the

distances. For example, the intensity of a sound 100 meters away from the source is one-

fourth as intense as it is 50 meters away from the source. The mathematical formula in this

example would be (50/100) 2 = _. Another example, the intensity of a sound 20 meters from

the source is 9 times the intensity of a sound 60 meters from the source, or (60/20) 2 = 9.

Acoustics

The word acoustic comes from the Greek language and means "to hear". Acoustics is

sometimes referred to as the science of sound. More often it is referred to as

architectural acoustics, which is the design of a building's acoustical environment. Recently,

this has become a greater area of study.




Marcus Pollio, a Roman architect who lived in the first century BC made important

observations on acoustics, and formed hypotheses on reverberation and interference. The

scientific study of acoustics was not done until 1856 by the American physicist Joseph

Henry. Wallace Sibine, another American physicist, later studied acoustics in more detail in

1900.

Sound reflects off any surface the waves encounter. Rooms can be designed and built for the

best natural reflection with no undesired distortion. Architects use materials that help

enhance reflection and absorption of sound. Cork and felt are good acoustical dampers while

metal and stone reflect sound. A roomies acoustics are usually good if there is a balance

between reflection and absorption materials.

The science of acoustics is of great concern when designing sound barriers, not only for roads

and highways, but in all necessary locations.

Noise

Noise has been defined in many ways. The Council on Environmental Quality defines noise

as "sound without value." The World Book Encyclopedia Dictionary entry states that noise is

"a sound that is not musical or pleasant". The American Standards Association calls noise "an

undesired sound". Encartaís article on noise says, "Noise is a complex sound, a mixture of

many different frequencies or notes not harmonically related." AASHTO, the American

Association of State Highway and Transportation Officials calls noise "unwanted sound."

Noise can cause physical harm. If you are exposed to a sound of 120 decibels it is painful. If

you are exposed to a sound of 170 decibels, even for a moment, it will knock you

unconscious, and destroy your hearing.

People thought that noise just went along with progress, and that you had to put up with it.

We now know that noise can be reduced with out slowing down progress. Some people donít

mind some noise, while others donít like it at all. We use sound barriers along highways and

other locations to reduce noise to a tolerable level.




There are three major ways of reducing highway noise. The first way is to improve cars so

that the engines and other parts run quieter, which will reduce the noise by 5 to 10 decibels.

The next way to reduce noise is to leave open spaces between highways and houses when

either is being designed and built. You could also put less noise-sensitive buildings or

facilities next to the roads. The last way is to use sound barriers or other noise reducing

measures if the noise level is above standards.

Sometimes insulation can be used in buildings to reduce noise. This is usually not a very

good idea because the road contractors donít have the authority to insulate buildings, and if

buildings are insulated, then you would have to spend more money on air conditioning since

there is no way for air to easily flow in and out.

There are several other ways to solve the noise problem when building new roads. You can

build away from noise-sensitive areas and through non noise-sensitive areas or through

undeveloped land. Constructing partially underground, so walls on side deflect noise from

residents is also an easy possibility. Making the road level the best that is possible so car

engines donít work as much on hills can also reduce sound.

Equipment to measure a sound in db unit




THREE TYPE SOLLUTION TO CONTROL TRAFFIC NOISE POLLUTION

1. INFORCEMENT BY THE GOVENRMENT ESSPECIALY DEPARTMENT OF

ROAD TRANSPORT OR PDRM.

2. MATERIAL THAT WE USING TO BUILD A

ROAD AND THE DESIGNING OF THE

ROAD (ALLIGMENT OF THE ROAD)

3. SOUND BARRIER AT THE

RESIDENT AREA


Type of surface Road alignment



INFORCEMENT BY GOVERMENT

The sound or noise make by vehicle that we ear actually come from :

1. Engine – 10% - 50 %

2. Friction between tire and road surface – 5% - 25%

3. Exhaust – 50% - 80%

4. Other part of vehicle such as blow off that have a turbo engine, suspension,

brake, aero down force, horn – up to 75%

JPJ one of enforcement department have a regulations to solve this problem especially

sound that came from exhaust. Commonly motorcycle, one group of riders make noise

up to 120db when they travel at 100km/h. It to easy to make an illegal exhaust system

that make noisy by modified an original factory standard part or buy after market part.

In year 2001 a more 100 summon was issue by JPJ it all about riders that modified

their exhaust to increase the sound.

Unfortunately JPJ don’t have an act about the limit of exhaust sound that can we

measure by decibel unit. The summon has issued it a about only modification of

exhaust. How about a motorcycle such a Harley – Davidson when it came out from

factory the sound it make up 100db when at certain rpm..?

Government for further action must control or warning shop that supply illegal car

part or accessories that can make a noise in road.

In future, cabinet as a voice represent of resident can create an act solve this problem

by limit the noise from exhaust or other part to one db unit.




DESIGN CRITIRIA

This is a part of engineer must take action, by design the surface of road using a

special material can reduce up 10 % sound from friction tire and road surface.

At Kuala Lumpur have a one road that using a Porous Asphalt road surface. That road

connecting Kuala Lumpur and Klang famous as Federal Highway. The road maintains

by Public Works Department, Dewan Bandaraya Kuala Lumpur (DBKL) and Projek

Lebuh Raya Utara Selatan (PLUS). Actually not along this road using porous asphalt

road surface, only 9 KM started at DBKL border and ending at junction to Subang

Air Port (PLUS border).

The main function this road surface is to flow the rain water to sub surface road and

increase the skid resistance but it can reduce the noise because the surface it self have

a many small hole that can absorb sound.

Source: National Asphalt Pavement Association (NAPA)

http://www.hotmix.org/images/stories/porous_asphalt_poster1.pdf



http://www.hotmix.org/images/stories/porous_asphalt_poster1.pdf


ROAD ALIGNMENT

Other way to control noise pollution is road alignment. Construct a new road crosses

resident area not a good idea. Engineer must choose a effective alignment to build a

new road by thinking a effect of noise pollution to existing resident area.

Make a new road with an alignment a cross tree area can reduces a noise that come

from traffic. Tree and a floor of jungle/bushes can be as acoustic wall absorb sound.




SOUND BARRIERS

Sound barriers are being used more and more as the demand for reduced noise along

highways becomes greater and greater. Sound barriers are built on new as well as existing

roads. The U.S. Congress passed legislation in 1976, which required states to reduce noise

along highways beside impacted areas. The federal government pays for most of the barrier

construction, and the state pays for the rest. Noise barriers reduce the decibel level by 10 to

15 decibels, which is cutting the sound in half. Usually you get a one decibel reduction for

every two vertical feet of barrier added, though the effectiveness and costs evens out at about

13 feet in height.

Types

There are two main types of noise barriers: earth berm and noise walls (concrete, masonry,

wood, etc.). Construction can include each type separately or in combination. You use the

noise readings to help decide the type, location, length, and height of a noise barrier. The

visual look also is a factor that decides which type to build at the given site. Vegetation is

sometimes used for noise reduction.

Noise walls can be constructed out of concrete, stucco, masonry, wood, and metal. There are

a variety of designs and styles used depending on what is needed at the location. They are

designed to blend into their surrounding but still be effective.

You should use an earth berm for visual looks, but only if the materials and room allows. An

earth berm blends in with its surroundings very well, and can have plants added to it to

virtually cover it up. An earth berm usually should not have a slope steeper than about a 22º.

Vegetation can be used if it is tall enough and it is dense enough (you canít see though it).

Vegetation at least 200 ft thick can give a 10 decibel reduction. It is usually impractical to put

in vegetation, because of cost and because there is usually not enough room.

Design and Construction

The engineer designing a sound barrier must consider the most effective way to reduce noise

with its location and design. A sound barrier will only work if the residents behind it canít see




the road (meaning that they are in the shadow zone). The barrier wonít work for residents

above wall, such as on a hillside, and homes that are too far apart make it very hard to build a

barrier for a reasonable cost. Sections that are taken out (not put in) of sound barriers for

roads or other purposes reduces the effectiveness of the barrier, since the sound is able to

travel through the opening.

The following are some of the considerations for the construction and design of a sound

barrier:

The desired noise reduction

The right of way needs and maintenance

Cost and constructability

Maintenance

Wind

Soil type

Earthquakes

Vehicle impacts

Vehicle access( to and through it)

Pedestrian access

Matches other structures around it (design, looks)

Drainage

Water/Electricity

The moving of objects or buildings to put in the barrier.

There are several other prospects for an engineer to consider when designing sound barriers.

Here are some factors that help calculate the sound produced by traffic:

2000 cars per hour is twice as loud as 200 cars per hour.

Vehicles traveling at 65 miles per hour sound twice as loud as vehicles traveling at 30

miles per hour.

1 truck traveling at 55 miles per hour is the same as 28 cars traveling at 55 miles per

hour.




Defective mufflers, other faulty engine parts, hills (making the engine work harder), the

engine itself, aerodynamics, and the tires on the road can all contribute to traffic noise.

Traffic noise has a frequency of about 550 hertz, so engineers also have to know how to

design a sound barrier with these frequencies.

Engineers will only design a sound barrier for an area if it is an impacted location. An

impacted location is an area used by humans where traffic noise (during the design year)

equals or exceeds 66 dB. The level is set at 66 dB because 2 people canít have a normal

conversation from 1 meter apart.

Sound decreases 3 to 4.5 dBA as the distance from the source is doubled because of objects

that deflect the sound, and because sound also gets weaker as the distance from the source

becomes greater. Generally, a distance farther than 500 ft from heavy traffic on a freeway is

not a major concern. On lightly traveled roads distances of 100 to 200 feet from traffic is not

a major concern either.

Another consideration is wind. You need a taller sound barrier for wind that is traveling with

sound just as in the concepts in "Characteristics of Sound." If you have a wind travelling

against the sound, the barrier doesnít need to be as tall.




CONTRUCTION IN MALAYSIA

Taman Permata – Middle Road Ring 2 (MRR2) Kuala Lumpur cost about RM600,000 done at

September 2006, constructed by TalentTwo (M) Sdn. Bhd.

That project manage by Road Branch Public Work Departmen and maintance by DBKL.

Below there is some during contruction




Taman Midah - Middle Road Ring 2 (MRR2) Kuala Lumpur cost about RM350,000 done at

September 2006, constructed by TalentTwo (M) Sdn. Bhd.



a way to reduce traffic noise pollution

Documents