NOISE BARRIERS – NATURAL AND MAN MADEBenafsha Wadiwalla

Roll No.

SYJC

WHAT ARE NOISE BARRIERS?

Noise barriers also called - soundwalls, sound berms, sound barriers, or acoustical barriers

It is an exterior structure designed to protect inhabitants of sensitive land use areas from noise pollution.

WHAT ARE NOISE BARRIERS?

Noise barriers are solid obstructions built between roadways and residential areas.

These barriers do not block all noise, they only reduce the overall noise level.

Effective noise barriers typically reduce noise levels by 5 to 10 decibels (dBA).

Subjectively, a 10 dBA increase in sound doubles the perceived or apparent loudness of a sound, while a decrease of 10 dBA halves the loudness experienced.

WHY NOISE BARRIERS?

Noise barriers are the most effective method of mitigating roadway, railway, and industrial noise sources – other than cessation of the source activity or use of source controls

HOW DO NOISE BARRIERS HELP?

There are basically two ways in which barriers reduce noise They either reflect the noise or they partially absorb noise.

Reflective barriers may be constructed out of any dense material

Partially absorptive barriers usually have a perforated skin and a chamber behind into which the sound waves enter and get dispersed.

EFFECTIVENESS OF NOISE BARRIERS

When the line of sight is blocked between the noise source and the receiver, a reduction of a least 5 dBA is achieved.

For each additional metre above line-of-sight, a reduction of an additional 1.5 dBA is achieved

BENEFITS

The benefits of noise reduction far outweigh aesthetic impacts for residents protected from unwanted sound. These benefits include

lessened sleep disturbance, improved ability to enjoy outdoor life, reduced speech interference,  stress reduction, reduced risk of hearing impairment, and a reduction in the elevated blood

pressure created by noise that improves cardiovascular health.

DISADVANTAGES OF NOISE BARRIERS INCLUDE:

Aesthetic impacts for motorists and neighbors, particularly if scenic vistas are blocked

Costs of design, construction, and maintenance

Necessity to design custom drainage that the barrier may interrupt

TYPES OF NOISE BARRIERS

Natural

Man made

NATURAL NOISE BARRIERS

Natural noise barriers use natural barriers such as plants and trees to reduce and absorb noise

NATURAL NOISE BARRIERS

The main aspects of good environmental noise barrier design include the appropriate manipulation of elements and materials and most importantly incorporate the use of plants.

When designing noise barriers, plants should always be considered as part and parcel of the design.

Plants not only help to integrate the barrier into its surroundings, by reducing apparent scale and screening elements, but they can also provide an aesthetic contribution

PLANTS AS NOISE BARRIERS

A thick hedge of evergreen trees can from a nearby noise source

Two or three rows of plants can cut down noise by more than seven decibels.

THE IDEAL NOISE BARRIER

The ideal noise barrier hedge is dense and tall enough that you can’t easily see through or over it

The effect is bolstered by planting vegetation in multiple rows and multiple tiers

You can enhance your noise barrier even more by first installing an earthen berm of several feet

POSSIBLE TREE SPECIES

A number of species offer good potential as noise-screening plantings.

Western hemlocks can grow closely together and their interlacing sprays of foliage create a dense mask.

Other members of the cypress family are commonly planted as hedges and can achieve a buffering effect with tight-packed scaly foliage and interlocking canopies.

PLANT QUALITIES

Evergreens with thick leaves and dense foliage soften the most noise.

When planting a hedge to reduce noise, it is most effective to choose plants that have branches extending all the way to the ground.

Gardeners who choose to plant trees with branches that do not grow near the ground should consider also planting a row of shorter hedges in front of the trees to block sound waves near the ground.

MAN MADE NOISE BARRIERS

Such noise Barriers are typically made from concrete, steel, vinyl, wood or earth mounds called ‘berms’.  

Berms are pretty good but in order to get them high enough to be effective sound barriers, they have to be so wide they take up huge amounts of valuable land. 

MAN MADE NOISE BARRIERS

Steel barriers are expensive, subject to corrosion and dent badly.

Concrete sound barriers are incredibly heavy, very expensive and are subject to needing replacement in as little as 10-20 years. 

Properly engineered vinyl barriers are a good alternative for commercial establishments 

EXAMPLES

The sound tube in Melbourne, Australia, designed to reduce roadway noise without detracting from the area's aesthetics.

Noise barrier earth berm along Highway 12, Sonoma County, California

CONSTRUCTION OF NOISE BARRIERS

With regard to construction costs, a major factor is the availability of excess soil in the immediate area which could be used for berm construction.

If the soil is present, it is often cheaper to construct an earth berm noise barrier than to haul away the excess dirt, provided there is sufficient land area available for berm construction.

KEEPING THE NOISE DOWN!!

A sound occurs when an ear senses pressure variations or vibrations in the air.

Noise is unwanted sound. The brain relates a subjective element to a sound, and an individual reaction is formed.

Numerous studies have indicated that the most pervasive sources of noise in our environment today are those associated with transportation.

Highway traffic noise tends to be a dominant noise source in our urban, as well as rural, environment.

HIGHWAY TRAFFIC BARRIERS AT A GLANCE: Can reduce the loudness of traffic noise by as much

as half Do not completely block all traffic noise Can be effective, regardless of the material used Must be tall and long with no openings Are most effective within 61 meters (200 feet) of a

highway (usually the first row of homes) Must be designed to be visually appealing Must be designed to preserve aesthetic values and

scenic vistas Do not increase noise levels perceptibly on the

opposite side of a highway Substantially reduce noise levels for people living

next to highways.

USE OF NOISE BARRIERS IN MUMBAI

The MMRDA, which had undertaken a study on noise barriers under the Mumbai Urban Transport Project, had first installed sound barriers

The cost of the same was Rs 8.68 crore on a 1,150-metre stretch at BKC,

It helped in slashing noise in the area to 55 from 98 decibels.

USE OF NOISE BARRIERS IN MUMBAI

The MMRDA plans to install noise barriers across highways such as Sion flyover, Kings Circle flyover, Hindamata flyover and Lalbaug flyover

The flyovers are flanked by residential areas, schools and hospitals on both sides.

The IIT Powai campus already has such barriers in place to cut decibel levels from the adjoining flyover.