I have an idea for an audio product what should I do?

Think Really Hard about the intended market....

There's a lot of shipwrecks on the reefs of broken schemes.

And the debris of the digital boom is everywhere, hence the term:

vaporware.

But good fortune to you anyhow.... ;)

Remember the big blue meters. That gets ‘‘em every time. 

Search in patents

Is it patentable? search

File for patent, take help of patent lawyers.

Everything else comes after. first patent.

I spoke to a patent attorney way back in the day and he thought I had a good idea and told me to imagine myself running the hurdles, in a dense fog, with the hurdles spaced indiscriminately and that there was no end to the race. 

Also, if someone were to steal your idea, it would take well over a year for a favorable judgment and the thief of your idea would still be cranking out your product, making money off of it. 

Needless to say, I didn't go through with it due to lack of resources on my end. Do your due diligence, as advised.

All the best,
Nonoise

Generally, you need some very detailed proof that what you are designing hasn’t been done before to get a patient.