498 Sound WavesQ17.6When listening, you are approximately the same distance from all of the members of the group. Ifdifferent frequencies traveled at different speeds, then you might hear the higher pitchedfrequencies before you heard the lower ones produced at the same time. Although it might beinteresting to think that each listener heard his or her own personal performance depending onwhere they were seated, a time lag like this could make a Beethoven sonata sound as if it werewritten by Charles Ives.Q17.7Since air is a viscous fluid, some of the energy of sound vibration is turned into internal energy. Atsuch great distances, the amplitude of the signal is so decreased by this effect you re unable to hearit.Q17.8We suppose that a point source has no structure, and radiates sound equally in all directions(isotropically). The sound wavefronts are expanding spheres, so the area over which the soundenergy spreads increases according toAr=42π. Thus, if the distance is tripled, the area increases by
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