Page 133 - The Master Handbook Of Acoustics
P. 133
108 CHAPTER FIVE
120
50–8,500 Hz
100 75 dB
Sound - pressure level, dB 80 Music
60
40
20
0
20 50 100 300 500 1 k 3 k 5 k 10 k 20 k
Frequency - Hz
FIGURE 5-14
The portion of the auditory region utilized for typical music sounds.
unpleasant thing we call noise or a carrier of information. The noise of
an automobile conveys considerable information on how well it is run-
ning. One person’s noise might be someone else’s communication. A
high-fidelity system can produce some beautiful sounds deemed very
desirable by the owner, but to a neighbor they might not be considered
beautiful at all. Sometimes it isn’t easy to distinguish between informa-
tion and noise. The same sound can be both. Society establishes limits
to keep objectionable noise to a minimum while ensuring that informa-
tion-carrying sounds can be heard by those who need to hear them.
Noise—The Good Kind
A good kind of noise? Defining noise as unwanted sound fits the sys-
tem noise considered previously, but noise is becoming an increas-
ingly important tool for measurements in acoustics as discussed in
Chaps. 5 and 7. This good noise is not necessarily different from the
