Everyday noise exposure over time has an impact upon our ability to hear and on the degree of hearing loss that develops. Constant exposure to loud noise can cause high frequency sensory neural hearing loss.
An exposure of 90 dB (which is equivalent to the noise made by a power lawn mower or passing motorcycle) is allowed for 8 hours, 95 dB for 4 hours, 100 dB only for 2 hours, 105 dB ( power mower) for one hour and 130 dB for (live rock music) 20 minutes.
Listening to music at 110-120 dB damages the hearing in less than an hour and a half.
A short blast of loud noise - greater than 120 to 155 dB - such as from fire crackers can cause severe to profound sensorineural hearing loss, pain, or hyperacusis (pain associated with loud noise). Most unregulated large bombs can produce a noise of more than 125 dB. Hence, the manufacture and sale of fire crackers generating a noise level of more than 125 dB at 4 meters distance from the point of bursting are prohibited.
The permissible noise limits in residential areas are 45 dB in night time and 55 dB in day time.
The limits are 50 dB in daytime (6am to 10 pm) and 40 dB in night time (10 pm to 6am) in Silence zones, which are areas up to 100 meters around hospitals, educational institutions and courts.
A normal conversation is about 60 dB. Noise from other rooms, hallway noises, or noise within the hall itself such as conversation of the audience, noise from AC/fans, phones ringing, turning paper, etc. adds to the decibels.
Background noise interferes with auditory communication and adversely affects speech perception and speech recognition. It also affects attention and memory. For a proper attention span, the noise levels should be below 50 dB.
Exposure to noise beyond permissible limits is a health hazard. Noise is a major avoidable cause of hearing loss. It not only affects the ears but the entire human body. The heart rate and BP increase. Noise at night disturbs sleep, especially for the elders and young ones. Sounds above the permissible level produces personality changes, affects human productivity and also increases the formation of free radicals in the human body.
It is recommended that people who are continuously exposed to a noise level of greater than 85 dB should be provided hearing protection in the form of muffs or plugs.
Vedic literature has described four gradations or levels of sound: Para (background noise of nature, no spoken sound), pashyanti (observed sound or perceived in mind), madhyama (audible sound), and vaikhari (articulated sound or spoken words). We should speak in pashyanti and madhyama.
Noise shifts the body to sympathetic mode and takes us away from conscious-based decisions. Hence, we should make an effort to speak softly to minimize the ambient noise levels.
Dr KK Aggarwal
Padma Shri Awardee
President Elect Confederation of Medical Associations in Asia and Oceania (CMAAO)
Group Editor-in-Chief IJCP Publications
President Heart Care Foundation of India
Immediate Past National President IMA