Noise pollution: Does your hearing get affected due to festivals?
Dr Kalyani Mandke 24 September 2012

We cannot stop hearing at any time of the day. Naturally our auditory system experiences fatigue because of noise pollution. There are many known ill effects, such as insomnia, irritability, lack of concentration and poor attention span. We all have right to be human beings with good quality of life.

There has been enough discussion about noise pollution. There are people who want to abide by rules and provide quality of life to all. And there are others who have single motto, “It’s my choice to play the music at whatever level I want”. The war is between them and us.


People forget that one cannot confine the noise levels to a certain area. Noise travels in all directions, and hearing is also not a voluntary act. We cannot stop hearing at any time of the day. Our process of hearing is active for 24x7. Whether you like it or not, one needs to hear all kinds of sounds because it’s around us. Naturally our auditory system experiences fatigue. There are many known ill effects of it, such as insomnia, irritability, lack of concentration and poor attention span. We all are not aspiring to be great thinkers, philosophers, or scientists but we all have right to be human beings with good quality of life.


Frequency parameter of sound: All the rules have been talking about the loudness of sound i.e. the output in decibels (dB) and the prescribed levels by the noise pollution rules of the year 2000. We need to understand another major component of sound i.e. frequency. For any given sound there exists frequency and intensity. We cannot have only intensity i.e. loudness and no frequency.


Whenever a sound is generated it implies that an object vibrates and certain frequencies are generated, and amount of force applied to the source will define the intensity. So when I clap there will be some frequency and at some intensity. If I clap forcefully intensity will increase but frequency will be same.  In another situation; you tap on the plain surface depending on the material you will hear different types of sound, that tonal percept is indicating different frequencies. It suggests that different frequencies are generated from different types of material.  Human ear can hear in a frequency range of 20Hz to 20,000Hz, and we hear all these frequencies in the range of 0 decibel (dB) to 120 decibel (dB). Unfortunately, our focus has been on this decibel but not on frequencies.


Frequencies are injurious to health: We need to understand that certain frequencies are injurious to health. This has become obvious because of current discussion of traditional instruments used in this Ganesh festival. These are considered as substitute for loud speakers.  It is certainly a strange assumption and it’s hard to understand on what grounds Police Department has given a nod to this option. These instruments certainly generate significantly louder sound, and these instruments will cross the prescribed noise level stated in the noise pollution rules.  Here we need to understand the frequency spectrum. Traditional instruments ‘Dhol’ and ‘Tasha’ may be more injurious to health.


Dhol generates low frequencies, and low frequencies always give a volume, though on intensity scale the level may not be very high, but psychological percept of this sound will be very loud. Low frequencies are actually transmitted into human body more easily, and would create more harm to the human body. The person who plays this instrument ties the Dhol on his/her waist. Naturally maximum sound energy will be transmitted to a human body. And others who are passing by this dhol player also get affected. People often feel vibrations in the chest, which implies that our lungs vibrate with these external sound sources. Vibrations of organs and soft tissues in the body are certainly injurious to the human body. There is adequate research available on the topic called as Human body Vibration. Let us try to understand this concept.


Human Vibration: Human vibration is defined as the effect of mechanical vibration on the human body. During our normal daily lives we are exposed to vibrations of one or other sort e.g. in buses, trains and cars. Many people are also exposed to other vibrations during their working day, e.g. vibrations produced by hand-tools, machinery, or heavy vehicles, etc.


Just as sound can be either music to the ear or irritating noise, human vibrations can either be pleasant or unpleasant. We enjoy, and even create pleasant vibrations when we run, dance, but we try to avoid exposing ourselves to unpleasant vibrations such as travelling on a bumpy road or operating hand-held power tools.


A good deal of research has been done in studying the effect of exposure to vibration on man, especially in his working environment. Some of the early research involved a study of people such as aircraft pilots, operators of heavy work vehicles and hand-tool operators. Their ability to perform complex tasks under adverse vibrational conditions formed part of the first investigations. Nowadays, human vibration research is also carried out in working environments and the results used to establish international standards, which allow human exposure to vibration to be evaluated.


Types of vibrations: There are two main types of human vibration: whole-body vibration and hand-arm vibration. Whole-body vibration is transmitted to the body as a whole, generally through the supporting surface (that is, feet, buttocks, back, etc.). A person driving a vehicle, for example, is subjected to the whole-body vibration through the buttocks, and if there is back support, through the back as well. Hand-arm vibration is transmitted to the hands and arms. Operators of hand-held power tools mainly experience it. Individuals who are playing dhol will have whole body vibrations transmitted through chest, lower waist, legs, and hand-arm vibrations as well.


 Exposure to whole-body vibration can either cause permanent physical damage, or disturb the nervous system. Daily exposure to whole-body vibration over a number of years can result in serious physical damage, e.g. ischemic lumbago, which is defined as a pain in the lower back and buttocks caused by vascular insufficiency. This is a condition affecting the lower spinal region. Exposure can also affect the exposed person's circulatory and/or urological systems. People suffering from the effect of long-term exposure to whole-body vibration have usually been exposed to this damaging vibration in association with some particular task at work. During Ganesh festival season, enthusiastic people have been practicing these traditional instruments for hours together, and for weeks. Naturally their bodies will be subjected to these unnatural vibrations. The younger generation may not take note of the damage happening to their body and internal organs. But these whole body vibrations are certainly silent killers.


Exposure to the whole-body vibration can disturb the central nervous system. Symptoms of this disturbance usually appear during, or shortly after exposure in the form of fatigue, insomnia, headache and ‘shakiness’. Many people have experienced these nervous symptoms after they have completed a long car trip or boat trip. However, the symptoms usually disappear after a period of rest. But recurrent exposure of whole-body vibration will lead to permanent damage of tissues.


Daily exposure to hand-arm vibration over a number of years can cause permanent physical damage usually resulting in what is commonly known as “white-finger syndrome”, or it can damage the joints and muscles of the wrist and/or elbow.


White-finger syndrome, in its advanced stages, is characterized by a blanching of the extremities of the fingers, which is caused by damage to the arteries and nerves in the soft tissue of the hand. The syndrome usually affects one finger first but will affect the other fingers also if exposure to hand-arm vibration continues. In the most severe cases both hands are affected. In the early stages of “white finger syndrome” the symptoms are tingling, numbness, and loss of feeling and control in those fingers which are affected. These symptoms are serious as they affect not only working activities but also leisure activities and they are, to a large extent, irreversible.


Loss of feeling and control of the fingers, even for short periods of time, can present a direct and immediate danger. E.g. when periods of exposure (use of vibrating hand tools) are alternated with precision handwork. This job situation is often found e.g. in abattoirs, where butchers use both circular saws and sharp knives. Same will be true for drum and tahshe beating for hours.  Damage to the wrist or elbow joints is often caused by long-term exposure to the vibrations produced by low blow rate percussive tools (e.g. asphalt hammers and rock drills). This damage causes pain in the joints and muscles of the forearm and is accompanied by reduction of control and muscular strength in the forearm.


Frequency response of the human body

Mechanical vibration of a machine is caused by the moving components of the machine. Every moving component has a certain frequency associated with its movement so, the overall vibration transmitted to a human body in contact with the machine is made up of different frequencies of vibration occurring simultaneously. This is an important fact to take into consideration when measuring human vibration because the human body is not equally sensitive to all frequencies of vibration.


To understand why human beings are more sensitive to some frequencies than to others it is useful to consider the human body as a mechanical system. This system is complicated by the fact that: (a) each part of the body has its greatest sensitivity in different frequency ranges; (b) the human body is not symmetrical, and (c) no two people respond to vibration in exactly the same way


In human vibration measurements vibrations occurring in the frequency range from 0.1 Hz-1500 Hz is of greatest interest. Those vibrations occurring between 1 Hz-80 Hz are of particular interest when measuring exposure to whole-body vibration, and those occurring between 5 Hz-1500 Hz are of special interest when measuring exposure to hand-arm vibration.


Whole-body vibrations should be measured in the directions of an orthogonal co-ordinate system having its origin at the location of the heart .The longitudinal direction (head-to-toe), the body is most sensitive to vibrations in the frequency range from 4 Hz-8 Hz. Human response to vibrations in the front-to-back direction and side-to-side do not differ and, in this lateral (transverse) plane, human response is greatest in the frequency range from 1 Hz to 2 Hz.


Vibrations in the frequency range 0.1 Hz-0.63Hz are considered to be responsible for causing discomfort or acute distress (commonly known as motion sickness), in people who are exposed to them. Individual human reactions to vibrations in this frequency range vary widely and are dependent not only on the vibration (motion) itself, but on factors such as vision, odour and age, which makes a study of this type of human vibration particularly complicated.


For the hand-arm system, the frequency response to vibration is the same in all directions.  It has maximum frequency sensitivity in the range from 12 Hz-16 Hz.


For all the traditional instruments used in this festive time have significant hand-arm vibrations, which would be injurious to health. For tasha there is another factor of high frequency exposure, since thasha generates high frequencies from 1500Hz and above which would be responsible for tinnitus (ringing in the ears). If our auditory system is exposed to high intensity sound like 110dB, some more changes occur in the nerve cell mechanism.



Nerve cells that carry electrical signals from the ears to the brain have a coating called the myelin sheath, which helps the electrical signals travel along the cell. Exposure to loud noises—i.e. noise over 110 decibels—can strip the cells of this coating, disrupting the electrical signals. This means the nerves can no longer efficiently transmit information from the ears to the brain.


This myelin sheath cannot be regenerated over and over again. That means people will develop hearing loss in their early life, which would be permanent type.  It is true for tinnitus as well. In early stage tinnitus can be temporary type, but over exposure to loud high frequency sound will lead to permanent type of tinnitus. Once tinnitus (constant ringing in the ear) is developed, it would lead to insomnia, irritability and difficulty in focusing.


Now it’s the call, what do you want? Short time fun and long time illness? Or healthy life for years to come.


(Courtesy: Awaaz Foundation)


(Dr Kalyani Mandke is specialist in Audiology and Speech Therapy. She is a Member of International Committee, American Academy of Audiology and has been instrumental in reviving the functioning Indian Speech and Hearing Association (ISHA).

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