Why is 96 kHz better?
It has to do with the Analog to Digital (A/D) converter. A Mr. Nyquist found out that the sampling frequency of an A/D converter must be twice the audio frequency we want it to convert. Humans hear up to 18 kHz, give or take, unless they have ruined their ears in front of Marshall stacks, 147 Leslie’s and other blasters.
So a converter with the traditional 44.1 or 48 kHz sampling rate can convert up to 22.05 of 24 kHz audio, well above what even a newborn can hear.
So why 96 kHz is better? To answer this question we have to dig deeper. If an A/D converter receives frequencies that are above the Nyquist frequency (e.g. overtones at 30 kHz) it does not simply ignore them. It ‘folds’ them back into the audible frequency spectrum, resulting in false tones. The solution to this problem is a filter in the analog part of the converter that filters all frequencies above 22 kHz, so they can’t fold back. These filters are called brick wall filters, because they stand there like a brick wall that doesn’t let anything trough. Unfortunately, small portions of the audio are bouncing back from this ‘wall’, creating so called artifacts (turbulence/ distortion) in the high frequencies that are audible.
By raising the sample frequency from 44.1 kHz to 96 kHz (audio from 22.05 to 48 kHz), the filter frequency can be raised too (from 22 kHz to approx. 35 kHz). The filter can be smoother (like tilting the wall). The back-bouncing gets reduced and only affects frequencies above 20 kHz.