This sounds like a good spring project for me:



This is the box I've discussed before here on the BBS. I want to see if I can actually make one. This is similar to a speed-controlled volume circuit, except that its attenuation is based on a microphone input rather than a speed input.

Its advantages over speed-controlled volume are:

- It does not require reading the car's OBD connector, or timing pulses of any kind. So in theory, the circuits should be simpler.

- It is based on a more realistic method of deciding when you would want to turn up your stereo. For instance, differences in road surface quality cause much more cabin noise than increased speed does. At least in my car.

The problem is that I've got no clue how to build the critical part of the thing. I figure that there's got to be a very simple way to do it with a few analog components. But I can't find any examples of it on the web. Anyone got any clues, links, or ideas?

There are two alternatives to this:

1. Find someone who already makes one. Problem is, I haven't found one. Anyone know of one?

2. Write some code to add in to Hijack that does essentially the same thing for the empeg, using the microphone connector. Problem is, I don't know how to do that, either. And it's spring, so Mark is out rock climbing, so I don't know if rubbing the genie lamp would work or not. Also, if I can make it in hardware instead of software, it can work for people other than empeg owners and I could theoretically market it for a profit.

So... Any ideas?