Whispering to a roar
NOISE influences human behaviour both physiologically and psychologically. At 0 decibels, the bottomline of hearing, the weakest sound can be heard in an extremely quiet environment. A soft whisper registers 20 dB and sleep is disturbed when ambient noise levels exceed 35 dB. Conversation is generally conducted at about 70 dB.
Noise levels above 80 dB begin to be bothersome and from 90 dB onwards they can cause harm. Sounds of about 150 dB can rupture the eardrum, but even at 90-120 dB, temporary or permanent damage to hearing can occur.
S K Kacker, director of the All India Institute of Medical Scientists and senior ENT specialist, says that noise causes stress-related illnesses and is also linked to neurological and gastrointestinal problems. Studies show that industrial workers exposed to high noise levels suffer cardiovascular disorders, allergies, sore throats and digestive disorders.
A study found 18 per cent of 75 normal healthy individuals exposed for 10-15 years to occupational noise of 88-107 dB for 6-8 hours per day suffered irregular cardiac rhythms compared to 6 per cent among 36 non-exposed individuals. Blood pressure and heart rate were significantly higher in the exposed group.
High-intensity noise can also cause headaches, nausea, instability, aggressiveness, anxiety and changes in mood. Irritability, fatigue and reduced productivity are the other adverse effects of long-term exposure.