Noise Exposure and Hearing Loss

Noise

Noise is a nonessential sound which causes disturbance. The intensity or loudness of sound is measure in decibels (dB). The scale of decibel is logarithmic which means three decibel increase in the level of sound represents doubling of the noise intensity. For example, a normal conversation ranges to about 60-65dB and someone shouting can range typically 75-80dB. The difference in decibels is only around 15-20 dB, but the intensity of shouting is 30 times. Since the human ear has different sensitivities to different frequencies, the unit to measure the strength or intensity or loudness of noise is usually measured in A-weighted decibels abbreviated as dBA or dBa or dB(A).

It is not just the loudness or intensity that determines the risk associated with noise, the span or duration of exposure is also very vital. Acknowledging this fact, time-weighted average sound levels are used. Typically for a noisy workplace this is based on 8 hours a working day.

The Ear, Hearing and Noise

With the invent of modern gadgets like smart phones, HiFi music systems, iPod or other music players, noise exposure is constantly increasing. Overexposure to noise for a longer and persistent period of time can lead to hearing loss (deafness) ranging from temporary to permanent.

The intense sound waves produced by the loud sounds (gunfire, shooting etc.) can damage the inner ear by damaging the hair cells of cochlea. When the ears are exposed to loud sounds for a short period of time, the person may experience a temporary threshold shift or more commonly a temporary hearing loss/impairment. This temporary hearing loss may be accompanied with ringing in the ears (tinnitus). One may recover gradually from temporary hearing loss. But, if the ear is exposed to loud sounds over longer and persistent period of time, the hair cells of cochlea can be permanently damaged, leading to the permanent sensorineural hearing loss.

Loudness of common sounds

Audiogram, speech Banana, Common Sounds
Fig 1: Audiogram of common sounds

Whisper:
30 decibels (dBa)
Normal Conversation:
60 decibels
An MP3 player at maximum volume:
105 decibels
Sirens:
120 decibels
Firecrackers and firearms (Gunfire or Shooting):
150 decibels
Cars to a close observer:
60 - 80 decibels


Hearing damage by sound loudness
Fig 2: Hearing damage with sound loudness

Anything above 85 decibels can cause permanent hearing loss

Prevention

You can prevent the hearing loss/impairment caused by the exposure to the loud sounds. Following can be done to reduce the noise-induced hearing loss:

  • Understanding which noises can cause damage (one's which are or above 85 dB).
  • Wear protective devices, like earplugs, earmuffs etc, when involved in the loud surroundings (e.g. around Gunfire or Shooting). You can get activity specific devices from hardware, medical or sporting goods stores.
  • Move away from the places where you are unable to reduce or protect yourself from noise.
  • Be vigilant to the hazardous noises in the surroundings. Protect the ears of children who are too young to take care of themselves.
  • Make your friends, colleagues and family aware of the hazards of noise.
  • Have your ear tested immediately if you suspect you might have hearing loss.