Noise Control & Design
Noise Control
Noise control is an important aspect of our daily life. Architects, Engineers and Highway Authorities are interested in this important field at the early design stage of a project, in order to incorporate the necessary environmental noise structures to allow comfortable living or working spaces. For an Architect the room or workspace placement and the selection of environmental materials are important considerations to ensure acceptable noise levels for residents in a building, such as a house, a school or a multi purpose hall.
For Engineers the position of a machine such as pumps, motors, fans, or blowers in a building generates noise and vibrations, and if these noise and vibrations are not managed properly, they will caused irritation to residents or workers within the affected zone. External Noise also frequently comes from moving vehicles on roads and highways, especially when heavy vehicles or heavy traffic accelerates. Besides commercial vehicles, aircraft and trains also generate noise.
Persistent noise disturbance affects human beings in many negative ways. Hence noise abatement is a critical aspect of today’s living. Noise and vibration control are specialized fields of Mechanical Engineering and various solutions are available to effectively reduce noise and vibration transmission. ,
What is Sound and Noise?
Sound is generated from a source and exist as a wave causing an alteration of air pressure in a space where there are particles to transmit the sound energy. The particles vibrate and propagate the sound energy along the material and the material could be air, gas, liquid or solid. In the absence of any particles like in a vacuum, sound transmission is not possible.
Noise is unwanted sound that is disturbing and undesirable. These are persistent loud sounds generated by vehicles, aircrafts, machines or equipment that affects human hearing. Exposure to these persistent loud noises for a long duration would cause issues, such as poor concentration, or even noise related illnesses such as loss of hearing. If left uncontrolled, this noise will disrupt our daily lives.
Sound levels are measured in dBA. Sound pressure levels in decibels (dBA) are defined as 20 times the logarithm to the base 10 of the ratio of sound pressure to a reference sound pressure. Decibels do not add numerically as numbers and adding a sound level like 70 dB to another sound level of 70 dB gives only 73 dB since doubling power only adds 3 dB increase in sound pressure.
Noise Barrier Design Concepts
A noise barrier (also known as a sound barrier, or acoustical barrier) is an exterior structure designed to protect inhabitants of sensitive land use areas from noise pollution. Noise barriers are the most effective method of noise control for highway, expressway, railway and industrial noise sources.
Noise is unwanted disturbing sound emitted from a sound source and travel as waves through air or a media. Particles within the media vibrate, travel and are displaced causing a variation of pressure. Sound is a waveform and may be reflected, diffracted and refracted at boundaries. Because sound is a waveform it can be measured in various frequencies which is the number of cycles per second (cps) or other unit of time. The commonly used unit of measurement is Hertz, which is kilocycles per second (kc). The upper and lower limits of average human hearing is between 15 cps to 15 kc . The important measurement of sound is Velocity (V) which is wavelength (l) on frequency (f): V=l/f.
In air at frequency of 1,126 cps the wavelength is 1 foot. Noise Barriers come in a few different types, such as the Metal Noise Barrier, Noise Blankets, and Mansory Noise Barrier Walls. For Metal Noise Barrier Walls, the material used for the construction of this type of noise barrier walls are lightweight metal acoustic panels, which are constructed from a combination of Aluminum and Galvanized Iron (GI) sheet. These noise barrier wall panels are held together firmly by galvanized metal “H” beam post and hot dip galvanized for corrosion protection.
The material usually used for the construction of noise barrier walls are lightweight metal acoustic panels constructed from a combination of Aluminium and Galvanized Iron (GI) sheets. These noise barrier panels are held firmly together by metal H-beam post, which have been hot-dip galvanized for corrosion protection.
