I didn't know that was your line of work
I think the problem is that if you are talking about an analogue audio signal of a few hundred millivolts, then for 16 bit dynamic range you are literally talking about microvolts of noise being important.
the supply will be used as reference voltages on differential input amplifiers, so the noise will be amplified with the analogue signal. and as you know the switching supply noise is more difficult to filter because the harmonics are at all radio frequency, rather than harmonics of 50 and 60 hertz of a transformer power supply, where the transformer is itself a big inductor that helps the problem.
as you realise that's why the expensive soundcards have 'battleship' filtering, multiple layer ground planes, the shortest possible tracks not to act as radio frequency aerials, and grounded boxes over critical components etc.
I think the difference is that the human ear has an incredible dynamic range (logarithmic scale) and can detect subjective noise most efficiently down to levels that tax even sophisticated noise meters. So the cost of a 'silent' switching supply starts to rise analogous maybe to the cost of 'audio grade' soundcards compared to even good soundblasters.
my respects, my friend