“…results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the ‘hypersonic effect.” May explain why most listeners can hear a supposedly impossibly high-frequency difference between a 12 kilo Hertz square wave versus a 12 kilo Hertz sine wave.
More scientific evidence supports the need for accurate wideband amplification in subjectively “good sound”: Reproduction of high frequencies measurably and dramatically stimulates increased brain activity, and “…[listeners] felt the sound containing [high frequencies] to be more pleasant than the same sound lacking [high frequencies and ultrasonics]. These results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the ‘hypersonic effect.'”.