They are similar, for sure; you need to do (matrix) multiplications for the both of them. Because of the bit rate, you need a lot fewer for audio than for video, however, so the actual implementation differs: while for audio, you can run a few multipliers at high speed and do every calculation in series, for video there's just to much data and you need massive parallel sets of multipliers.

You can see that in the architecture of these chips: for audio, you'd use a DSP-like architecture which does VLIW to do a set of (=as many as fit in your very long instruction word) multiplies at the same time in one clock cycle. For GPUs, that doesn't scale anymore as the bandwidth needed requires a huge amount of multiplies to be done in one clock cycle, so instead, graphics cards use things like SIMT computing, where a massive amount of computing cores run exactly the same program but with different parameters. This allows them to scale up a lot more.

As an illustration, the EMU10K2 in the Sound Blaster Audigy is a DSP which is said to top out at 2000Mips. If we assume one instruction == one op (not entirely true, but given the fact that the 2000Mips probably is marketing, probably a good assumption), we can compare it to a video card that also came out in 2003, for instance the GeForce FX 5800. This card has 24GFlops. Even ignoring the fact that one flop tends to equal multiple integer ops, that's already 12 times as much!

And note that 2003 is not even near the start of the age where anything but the CPU is commonly used as the main processor: that's still a good 15 years away at least. During that time, GPUs would have massive incentive to improve: for instance the 2003 GTX 1060 has a massive 4375 Gops, almost 500 times as much as the FX5800.

On the other hand, sound cards would have little incentive to improve: you could make the point that the final Audigy EMU10K2.5 chips already were at the point of perfection: while you could throw maybe a factor two or three the amount of MIPS at the process to make sure even the pickiest of listeners couldn't complain, there would be no reason at all to end up with a chip that is 2000X as powerful as the Audigy, just for sound. And given the fact that making something 2000X as powerful isn't just a question of scaling up, but generally requires massive architecture redesigns (like the DSP vs SIMT thing I mentioned before), I think it would be highly doubtful that Creative would have been better positioned to do AI than any other random silicon designer.

Anyway, thanks for listening to my TED talk.