High Frequency Limits

Perhaps the most commonly known aspect of the psychoacoustic model is that humans cannot hear frequencies above and below certain thresholds; in fact, most humans can only hear frequencies between 20 Hz and 20.5 kHz. So-called "silent" dog whistles exploit this phenomenon by producing sounds at frequencies greater than those audible to humans but well within the range of a dog's hearing. Likewise, when compressing a digital signal, an acoustic engineer can safely assume that any frequency beyond approximately 22Khz will not have any effect on the perceived sound of the finished product, and set the sampling frequency to the calculated Nyquist-Shannon rate of 44Khz.