A: Sound level is measured in decibel (dB). The average loudness or intensity of sound is about 60dB for regular person-to-person conversations, 80–100dB in cinema halls, and 100–120dB at concerts. But intensity is not the only factor at play when it comes to hearing damage from loud sounds — duration of exposure to the sound is also important. 

It takes about eight hours of constant exposure to sound with an intensity of, say, 80dB, before some hearing damage takes place. For every 3dB increase in intensity, exposure time to the sound must be halved. This means that when the sound intensity is increased from 80dB to 88dB, only four hours of exposure is needed before some damage sets in. At 100dB, which is very loud, this goes down to three hours.

The ringing or muffled sounds that a person sometimes experiences after a loud concert usually go away within 48 hours.

The microscopic auditory hair cells in the inner ear sway when sound waves enter the ear. When the sound is very loud, the cells take more time to straighten. When the sound is too loud, the hair cells may be unable to straighten back and become irreversibly damaged. Damaged hair cells result in decreased hearing sensitivity. People with some damaged hearing, for instance, are often unable to distinguish between high-frequency sounds like ‘s’ and ‘th’.

Hearing loss may occur more commonly in older people — about 10 per cent of people above the age of 65 and 30 per cent of those above 80 have hearing loss — but it is not just an elderly problem.

Using ear buds to listen to music at full blast can mean being exposed to sound levels of about 100dB. With noise cancellation features in more advanced devices, keeping the volume at 60 per cent can allow listeners to enjoy their music for a longer period while protecting their hearing.