Page 143 - IGC BOOK

Loud noise is particularly harmful to the inner ear (cochlea). A one-time exposure to extreme
loud sound or listening to loud sounds for a long time can cause hearing loss. Loud noise can
damage cells and membranes in the cochlea. Listening to loud noise for a long time can
overwork hair cells in the ear, which can cause these cells to die. The hearing loss progresses as
long as the exposure continues. Harmful effects might continue even after noise exposure has
stopped. Damage to the inner ear or auditory neural system is generally permanent.

Terminology

Sound Pressure – the atmospheric pressure of sound waves moving through air. The unit of the
sound pressure is Pascal (Pa)

Intensity – the measure of intensity, which relates to how much energy the pressure wave has.
Loudness of sound is measured in decibels(dB).

Frequency - Pitch relates to the frequency, or how many times a second the particles vibrate.
The distance between one wave and the next gives the wavelength. For sounds all travelling at
the same speed, high-frequency (high-pitched) sounds have waves very close together. A normal
human ear is able to hear sounds with frequencies from 20 Hz to 20,000 Hz.

A Weighting - The most common weighting that is used in noise measurement is A-Weighting.
Like the human ear, this effectively cuts off the lower and higher frequencies that the average
person cannot hear. It is expressed in dBA or dB(A)
C weighting - The response of the human ear varies with the sound level. At higher levels, 100
dB and above, the ear's response is flatter, as shown in the C-Weighted Response to the right.

Although the A-Weighted response is used for most applications, C-Weighting is also available on
many sound levels meters. C Weighting is usually used for Peak measurements and in some
entertainment noise measurement, where the transmission of bass noise can be a problem. It is
expressed in dBC or dB(C).

ENSIGN | Unit IG2 – Element 5 – Physical and Psychological 3
Health