GALA / SDVC for Car Radios1.0 - Google Play

This App provides a speed-dependent volume control for Car Radios based un MCUs by microntek.

Why microntek?
It will only work if MCU controls sound and if it reacts to microntec-specific API-calls.
Enough Tech-Bla-Bla

For example HuiFei-Units (probably most Pure Android 4.x Headunits) rely on microntek-MCUs.
Just try and if it does not work give the app back within 30 minutes.
Further this App's price is to be seen as donation! You can get this App for free on XDA-Developers!
Just search the HuiFei-Headunit-Thread and look around pages 90-100.

You can configure three things:
Characteristic (3 or 5 steps)
Intensity (raise by one or two counters per step)
Notification (show a notification each time something happens - more for debugging than for real use)

Last but not least here is a table for the Steps. Each Step means Volume +1 (or +2 if using double intensity)

For 3-Step-Characteristic:
Step 0 < 55 km/h (no adjustment done)
Step 1 raise > 55
Step 1 lower < 45
Step 2 raise > 115
Step 2 lower < 105
Step 3 raise > 165
Step 3 lower < 155

For 5-Step-Characteristic:
Step 0 < 55 km/h (no adjustment done)
Step 1 raise > 55
Step 1 lower < 45
Step 2 raise > 90
Step 2 lower < 80
Step 3 raise > 140
Step 3 lower < 130
Step 4 raise > 180
Step 4 lower < 170
Step 5 raise > 205
Step 5 lower < 195