It’s all done with volleys, and Wever called his idea the volley principle. Picture in your mind a company of British Redcoats in the Revolutionary War (Earth, 1775-1783). The soldiers on the front line all fire their muskets and then kneel down to reload. While they are reloading, the second line fires, kneels, and begins to reload. Then the third line fires, kneels, and begins to reload. This sequence is repeated by the fourth line. By this time, the first line has reloaded, so they stand and fire, then kneel, and begin to reload. This is the essence of the volley principle. You get a rate of firing much higher than any individual soldier could fire by having groups of soldiers firing in volleys. Now think of groups of neurons in the auditory nerve doing the same thing as the groups of soldiers, firing in volleys to match the frequency of the sound.

Figure 9, here we could have a figure as simple as Figure 7.9 from Klein or an action figure with neurons like groups of soldiers, firing, then recovering while a second group fires and recovers, etc.

To summarize, the current theory of pitch perception has three parts: From about 20 Hz to about 400 Hz, Rutherford’s frequency theory accounts for pitch perception through the rate of firing of individual neurons. Next, Wever’s volley principle extends the frequency idea up to about 4 kHz. From there, von Békésy’s place theory takes over and explains our ability to discriminate pitches up to 20 kHz. Actually, both place theory and the volley principle hold for sounds from about 1 kHz to about 4 kHz, which may explain why we’re more sensitive to pitches within this range of sounds.