[shin_lao]

High sample rate isn't useful for playback, but 24-bit is great for nuance in low intensity sound.

[throwaway0665]

The noise floor of 16-bit music is imperceptible so for mastered music at least 24-bits is useless. Both a higher sample rate and bit depth can be useful for recording purposes - provided the room is perfectly treated and there are no external sources of noise.

[KeplerBoy]

so for stuff which didn't properly use the dynamic range of the standard codecs?

Are human ears even capable of hearing 24 bits of dynamic range?

[FabHK]

Rule of thumb:

We know that 2^10 ≈ 10^3, so 2^24 ≈ 10^(3/10*24) = 10^7.2. This 7.2 is about amplitude, but what we hear is power which is quadratic in amplitude, so take a factor of 2, and you're talking 14.4 bel, or 144 decibel for 24 bit (and 2/3 of that, 96 db, for 16 bit).

(In reality it's a bit more complicated, but that's a good rough guide, see https://en.wikipedia.org/wiki/Audio_bit_depth#Quantization)