High frequency limit

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The high frequency limit of hearing is the upper extent to which a particular animal can perceive sound.

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 20,000 Hz (E0 to D#10 in Scientific pitch notation). So-called "silent" dog whistles exploit this phenomenon by producing sounds at frequencies higher 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 20 kHz will not have any effect on the perceived sound of the finished product, and thus use a high-shelving filter to cut everything outside this range. The sound can then be sampled at the standard CD sample rate of 44.1 kHz (or 48kHz in DAT), set somewhat higher than the calculated Nyquist-Shannon rate of 40 kHz to allow for the cut-off slope of a reasonable band-pass filter.


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Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .

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