Do you hear a difference?

[David A]

It’s highly likely that as I approach 50, my hearing is not what it used to be and I can’t differentiate the higher kHz, 

No human being can hear above CD quality's top frequency so don't feel bad about it. Those who hear a difference are hearing a difference in mastering, not 30+ thousand Hertz.

Not so fast  :-)

Equipment generates harmonic distortion based on overtones of frequencies in the signal and it also generates intermodulation distortion based on frequencies related to the difference between frequencies contained in the signal. Take a look at the plots of intermodulation distortion occurring for tones of 19 and 20 kHz in John Atkinson's test reports of amps in Stereophile. Most of us here can no longer hear 19 and 20 kHz test tones yet the presence of tones we can no longer hear in a signal is capable of generating effects all the way down to 1 kHz which we most certainly can hear. I have a CD of Meredith Monk, an experimental composer and performer, running her moistened finger around the rim of a wine glass to produce one tone and singing a sound that starts off just below that pitch and increases to just above it and then going back below the pitch again and repeating this process for over a minute. Listen to the track and you hear a difference tone which appears to be located within your ear.

Once we start to consider overtones and difference tones, sounds above the limit of our hearing—whether that be the theoretical 20 kHz limit or our own personal hearing limit—can most certainly produce effects in the audible range. The fact that we may not be able to hear the frequencies in the signal doesn't prevent them from having effects in the audible range so what we can't hear can actually have an audible effect.

You can classify these effects as distortion and they certainly satisfy the strict definition of distortion but not all distortion is unpleasant and some distortions such as the first, second and third overtones actually which are also produced by instruments and voices actually contribute to the richness of musical sounds. Not all distortion is unpleasant.

It's easy to say that we can't hear frequencies above the limit of a CD's top frequency and that's true but that doesn't mean that frequencies above that limit can't have effects in the audible range and influence our perception of the tonal character of music.

The limits of our hearing are determined by listening to pure test tones of a single frequency. Music is made up of multiple simultaneous tones produced by different instruments or voices, or several tones produced at the same time by the one instrument, and even 2 tones produced simultaneously by the same voice in overtone singing, and all of those musical tones have overtones and difference products can occur between all of the frequencies involved. Overtones above the audible range do affect our perception of tonal characteristics off musical sounds.

Tests of our hearing ability done with single tones aren't a reliable guide to what we hear when we're listening to music with multiple simultaneous tones and the upper limit of our hearing as determined by single tone tests doesn't stop higher frequencies in musical sound having effects well within our hearing range.


I agree that the quality of mastering plays a part in what we hear and that  high res recordings are often mastered with greater care and attention which does make a difference but frequencies above the limit of our hearing do have effects which we can hear, even if we can't hear some of the frequencies contributing to those effects.

Things are usually a bit more messy than we'd like to believe and I don't think I've covered the whole mess on this issue.