Subject: The Intensity of Sound
The human ear responds to sounds of an
incredible range of intensity. The loudest sound
that a healthy person can hear without causing
damage to their ear has an intensity of 10 12
times greater than the weakest sound they can
hear. In order to avoid the use of numbers of a
large range, we use the logarithmic function,
which lowers the huge numbers of sound
intensity to a scale ranging from 0 dB up to 140
dB.
0 dB sound intensity that is equivalent to the threshold
of audibility.
140 dB, the sound intensity equivalent to the pain
threshold of the human hear.
The intensity of sound is calculated by the function D=10 . log (
in dB, is the intensity of sound in Watt/m 2 and
, where D is the intensity of sound
= 10 -12 W/m 2 is the minimum sound intensity.
• Activity 1
a) Make the subject of the above formula and sketch the graph.
b) What is the minimum value of ?
c) Describe the monotony of function .
d) Deduce if it is possible to sketch a graph of the reverse of , and if yes, sketch it.
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