High end equipment makers have a vested interest in promoting pseudo science because it duped people into spending $5k for a DAC (e.g., PS Audio). Audio frequency range electrical engineering is very well understood and rigorously defined. The only extent to which there is an ‘x’ factor not covered by the legit engineering is that human perception does play a role in, well, human perception. So if you tell someone that this piece of equipment cost more than a car, people will genuinely believe it does sound better. Not too dissimilar from the very real placebo effect in medicine.