| Signals and Systems for Speech and Hearing 2nd ed | "Under very favorable conditions most individuals can obtain tonal characteristics as low as 12 cycles |
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| , the least amount of intensity is needed to reach threshold in the 2000 to 5000 Hz range"• American Heritage Dictionary of the English Language 3rd ed |
"For auditory signals and human listeners, the accepted range is 20Hz to 20kHz, the limits of human hearing"• "hearing is most sensitive i.
8.