INTRODUCTION
Noise pollution, or noise disturbance, is annoying or excessive noise that can affect the activity or balance of human or animal life. Most of the world’s external noise sources are primarily caused by machinery, transportation systems, cars, planes and trains. External noise is summarized in the term environmental noise. Poor city planning can lead to noise pollution, as noise pollution can occur in residential areas in addition to industrial and residential buildings. Documented issues related to urban noise date back to ancient Rome. Machinery, construction work, and playing music can cause external noise, especially in some workplaces. Noise-induced hearing loss can be caused by external or internal noise. Noise pollution affects both health and behavior. Unwanted sounds (noise) can impair mental health. Noise pollution can hypertension, high stress levels, tinnitus, hearing loss, sleep disturbances, and other harmful effects
TYPES OF NOISE POLLUTION
1. LINE SOURCE: A line source, as opposed to a point source, or volume source, is a source of air, noise, water contamination or electromagnetic radiation that emanates from a linear( one dimensional ) geometry.
2. INDUSTRIAL NOISE: Industrial noise, or occupational noise, is often a term used in relation to environmental health and safety, rather than nuisance, as sustained exposure can cause permanent hearing damage. Industrial noise or occupational noise is the amount of acoustical energy (noise) received by an employees auditory system while they are working.
3. ROADWAY NOISE: Roadway noise is the collective sound energy emanating from motor vehicles. It consists chiefly of road surface, tire, engine/transmission, aerodynamic, and braking elements. In developed and developing countries, roadway noise contributes a proportionately large share of the total societal noise pollution.
4. AIRCRAFT NOISE: Aircraft noise pollution produced by any aircraft or its components, during various phases of a flight: on the ground while parked such as auxiliary power units, while taxiing, on run-up from propeller and jet exhaust, during take off, underneath and lateral to departure and arrival paths, over-flying while en route, or during landing.
5. JET NOISE: In aero acoustics, jet noise is the field that focuses on the noise generation caused by high-velocity jets and the turbulent eddies generated by shearing flow. Such noise is known as broadband noise and extends well beyond the range of human hearing. Jet noise is also responsible for some of the loudest sounds ever produced by mankind.
6. ENVIRONMENTAL NOISE: Environmental noise is the summary of noise pollution from outside, caused by transport, industrial and recreational activities.
Noise is frequently described as’unwanted sound’ , and, within this context, environmental noise is generally present in some form in all areas of human activity. The efects in humans of exposure to environmental noise may vary fro emotional to physiological and psycological.
7. WHITE NOISE: In signaling processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. White noise refers to a statistical model for signals and signal sources, rather than to any specific signal.
EFFECTS OF NOISE POLLUTION ON HEALTH
Noise pollution has certain effects on the environment as well as an individual. Some of these effects are hearing problems, cardiovascular issues, sleeping disorders and tinnitus. Animals also face problems because of noise pollution as the frequency of their hearing is higher.
1. NOISE INDUCED HEARING LOSS
Noise -induced hearing loss (NHL) is hearing impairment resulting from exposure to loud sound. People may have a loss of perception of a narrow range of frequencies, impaired cognitive perception of sound, or other impairment, including sensitivity to sound or ringing in the ears.
Hearing may deteriorate gradually from chronic and repeated noise exposure, such as a gunshot or air horn. In both types, loud sound overstimulates delicate hearing cells, leading to the permanent injury or death of the cells. Once lost, hearing cannot be restored in humans. When exposure to hazards such as noise occur at work and is associated with hearing loss, it is referred to as occupational hearing loss.
2. OCCUPATIONAL HEARING LOSS
Occupational hearing loss (OHL), is hearing loss that occurs as a result of occupational hazards. OHL, damage to one or both ears from exposures related to one’s occupation, is a large but preventable problem. Organizations such as the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) work with employers and workers to reduce or eliminate completely hazards to hearing. Occupational hearing loss is one of the most common work in the united states.
3. HEALTH EFFECTS FROM NOISE
Noise health effects are the health consequences of regular exposure, to consistent elevated sound levels. Elevated workplace or environmental noise can cause hearing impairment, hypertension, ischemic heart disease, annoyance, and sleep disturbance. Changes in the immune system and birth defects have been also attributed to noise exposure.
NOISE CONTROL
Noise control or noise mitigation is a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors.
1. SOUNDPROOFING
Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflector absorb the energy of the sound waves, using damping structures such as sound baffles, or using active anti noise sound generators.
Two distinct soundproofing problems may need to be considered when designing acoustic treatments- to improve the sound within a room, and reduce sound leakage to adjacent rooms or outdoors.
2. ABSORPTION (ACOUSTICS)
Acoustic absorption refers to the process by which a material, structure, or object takes in sound energy when sound waves are encountered, as opposed to reflecting the energy. Part of the absorbed energy is transformed into heat and part is transmitted through the absorbing body. The energy transformed into heat is said to have been ‘lost’. When sound from a loudspeaker collides with the walls of a room part of the sound’s energy is reflected, part is transmitted, and part is absorbed into the walls.
3. VIBRATION ISOLATION
Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations. Vibration is undesirable in many domains, primarily engineered systems and habitable spaces, and methods have been developed to prevent the transfer of vibration to such systems. Vibrations propogate via mechanical waves and certain mechanical linkages conduct vibrations more efficiently than others. Passive vibration isolation makes use of materials and mechanical linkages that absorb and damp these mechanical waves. Active vibration isolation involves sensors and actuators that produce destructive interference that cancels-out incoming vibration
4. ACOUSTIC QUIETING
Acoustic quieting is the process of making machienary quieter by damping vibrations to prevent them from reaching the observer. Machinery vibrates, causing sound waves in air, hydroacoustic waves in water, and mechanical stresses in solid matter. Quieting is achieved by absorbing the vibrational energy or minimizing the source of the vibration. It may also be redirected away from the observer.
One of the major reasons for the development of acoustic quieting techniques was for making submarines difficult to detect by sonar. This military goal of the mid- and late-twentieth centuary allowed the technology to be adapted to many industries and products, such as computers (e.g. hard drive technology), automobiles, and even sporting goods.
5. NOISE REGULATION
Noise regulation restricts the amount of noise, the duration noise and the source of noise. It usually places restrictions for certain times of the day.