SOUND -as we listen

Postby Gautam Shah



SOUND is sensorial perception received mainly through the Ears, but often through the Skin of the body. The ears are on either side of the body, and so are able to distinguish the sound from left or right fields. The ears are able to distinguish pitch and intensity of the sound and thereby roughly determine the source, its distance and the nature of medium through which the sound has arrived.


In technical sense Sound is caused by the Mechanical disturbance in a solid, liquid or gaseous materials. These materials have varying degree of Elasticity to act as the sound transmitting medium. The vibrating objects could be the vocal cords of a person, string and sound board of a guitar or violin, tines of a tuning fork, or the diaphragm of a radio speaker. Music is formed of one fundamental frequency, and several other integral multiples of this basic frequency, called harmonics. A pure Tone of sound, composed of only one frequency is one that is produced by a striking fork.


Sound producing or vocal organs are many such as: lungs, windpipe, throat, larynx, nose and mouth “The vocal organs –are primarily for breathing and eating. The lungs act as bellows. The vocal cords or folds of the larynx vibrate as double reeds. The cavities of the throat, nasal sinuses, and mouth act as resonating chambers, with the size of the mouth cavity varied by jaw movement.”

Human voice is more versatile than any other musical instrument. Sarangi (Indian musical instrument which has guts -instead of wires, and played with a bow, its markers are created by pushing the gut upward over the fingers) emulates sounds that are closer to human voice.


Vibratory energy that is perceived by the human ear or the audible sound is termed as audio or sonic. Audible range of frequencies for a normal young person is 20 Hz to 20000 Hz (1 Hertz = 1 vibration/second). Very low frequency (infra sound lower then 20Hz) or very high frequency (ultra sound beyond 20000Hz) are not perceived by the human ear. Actual audio capacity of an individual person varies a lot. Intelligible human speech occurs in the range of 600 Hz and 4000 Hz.

Caissons_grave_DSC_5563ECThe ears of children respond to very high frequency sounds which by adulthood narrows to about 15-15000 Hz. The loss of hearing in adolescence, approximately 80 Hz every six months, becomes noticeable years later. An aged person may not hear high frequency sounds such as ticking of a watch or certain high frequency consonant sounds.

EdisonLaboratoryMusicRoom1905smHuman ear or mind has enormous capacity to discriminate and to extract the required information from the background noise and signals. The Noise -the unwanted range of Sound is below 200 Hz. However it cannot separate out sounds that are close either in frequency or in time. A human ear has greatest sensitivity between 100-4000 Hz.


General room noise masks the traffic noise, making it less noticeable, or the traffic noise may mask the conversation taking place in the room. It often happens that in an attempt to reduce the external sound penetration through efficient insulation, enhances the internally occurring noises. Inversely by eliminating all the internal noises one may enhance the effect of sounds arriving from outside.


A modern good quality PA system should be capable of 100 Hz to 6000 Hz and preferably 10000 Hz. For music the PA system should be 80 Hz to 10000 Hz and up to 15000 Hz for high quality theatre type of installation. Some sound equipments include loudness control by attempting a degree of compensation by boosting bass and possibly treble at low listening levels.


This means that if a sound is reproduced at a higher level than at which it was recorded, then the low frequencies will become relatively louder (speech will sound boomy). If it is reproduced at a lower level then it will sound `thin’ and lack bass (orchestra reproduced at a small room level).