Summing mixer with dynamic volume control on one input

Other Hardware Audio
1

Hello everybody,

I want to build a simple, passive summing mixer. Normally, I wouldn't need volume control, and I wouldn't even need Arduino for that.

But what I would like to achieve is this: whenever there is a sound played on input #2, the volume on input #1 should dim a bit. Why, you may ask?

Well, this is for my car, for voice-over navigation.
The project is this:

  • on input #1 I will connect an audio player, and
  • on input #2 I will connect an aftermarket navigation.
    So, whenever the navigation will make an audio announcement, the music volume should be turned down a bit.

The question is: how can I detect that there is a sound on input #2? I thought about an envelope follower circuit, but there must be a simpler way... and the detection must be done instantly, so that the volume dimming could act properly, otherwise the navigation voice-over would overlap the music at about the same level.

What do you think?

2

I think you need a dynamic range compressor. These can be analogue or digital. I made a single channel digital version on an esp32 for Bluetooth audio but the code could be adapted to do some sidechaining if you wanted to go the digital route. If not digital, I believe there are ready-made compressors that will do this although they may be expensive.

3

Silkworm:
The question is: how can I detect that there is a sound on input #2? I thought about an envelope follower circuit, but there must be a simpler way...

Nope, that's how to do it, be it analog or digital in software.

4

I thought about an envelope follower circuit, but there must be a simpler way

What is complex about an envelope follower? One diode, one capacitor and one resistor.

the volume on input #1 should dim a bit.

The real term for this is ducking.