Audio Engineering

Acoustic Environment 89

It can be seen that the velocity is dependent only on the type of gas and the temperature
and is independent of changes in pressure. This is true because bothP and ρ decrease with
increasing altitude and the net effect is that atmospheric pressure has only a very slight
effect on sound velocity. Therefore the speed of sound at the top of a mountain would be the
same as at the bottom of the mountain if the temperature is the same at both locations.

3.7 Typical Wavelengths ................................................................................................

Some typical wavelengths for midfrequency octave centers are shown in Table 3.2.

Now suppose the temperature increases 20°F to 92.5°F.

49 45992 5. 1151 ft/s

The table of frequencies and wavelengths is shown in Table 3.3.

Table 3.2 : Typical Wavelengths for Midfrequency

Octave Centers

Frequency (Hz) Wavelength (ft)

250 4.52

500 2.26

1000 1.13

2000 0.57

4000 0.28

8000 0.14

16,000 0.07

Table 3.3 : Frequencies and Wavelengths

Frequency (Hz) Wavelength (ft)

250 4.60

500 2.30

1000 1.15

2000 0.58

4000 0.29

8000 0.14

16,000 0.07