3 ms·

How do we know that the trumpet still sounds harmonically pleasing above 20 kHz? It may sound nice to the human ear, and a horrible mess to anyone with ultrason

• kazinator 9y ago
  If we boost the frequencies even in just the range 10-20 kHz, things sound harsh and fizzy to the human ear. The frequencies there are no longer musical in the sense of being recognized as musical notes. That is to say, although in a pure arithmetic sense, frequency 148080 is an A, since it is a power of two multiple of 440; five octaves above it, we don't hear it as an A tone. The frequencies in that ballpark just have to be present to add a sense of "definition" or "crispness" or "air" to the sound. In fact, this can be faked! In the OPUS codec, there is something called SBC: spectral band compression. What this refers to is basically a hack whereby the upper harmonics of the signal are completely stripped away, and then re-synthesized on the other end based on a duplicate of the lower harmonics or something like that. The listener just hears the increased definition.