THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

3.10 Octave and One-Third Octave Bands in the Audio Range 45Figure 3.10. Impingement of sound waves on a partial barrier, with a resulting sounddiffraction and a shadow zone.The analytical treatment of sound barriers is covered in Chapter 12, but it sufficesfor now to say qualitatively that sound at lower frequencies tends to diffractover partial barriers more easily than sound at higher frequencies. Moreover, thesharpness and extent of the shadow zone behind the barrier depend on the relativepositions of the source and receiver. The closer the source is to the barrier, thelonger is the shadow zone on the other side of the barrier, i.e., the more soundreduction obtained.3.10 Octave and One-Third Octave Bandsin the Audio RangeFor analytical purposes, the audio range of frequencies are divided into 10 standardoctave bands with center frequencies f C = 31.5, 63, 125, 250, and 500 Hz, and 1,2, 4, 8, and 16 kHz. Each octave band-center frequency f C is double the precedingone and each bandwidth doubles the preceding one. The lower and upper limits of