Hi giuliomoro Apologies for the delay here, I was at a workshop!
Update on this issue:
The issue seems to persist with headphones that do not have a microphone (TRS) and that are factory-made.
What is strange is that when we send out audio on only one channel and measure output on both channels with an oscilloscope, we (correctly) see a signal on only one channel (the other channel reflects noise, as far as I can tell). So it is not clear why we are hearing a signal (faintly) when plugging the headphones in? I suppose it suggests a problem with our headphones, but I have tried several different pairs?
What is also strange is that when we send a signal out on only one channel through our full audio pathway (where we send the Left channel to both ears on one pair of headphones, and the Right channel to both ears on another pair of headphones), you can hear a faint signal in the headphones connected to the channel where there should be no signal, but only when both pairs of headphones are plugged in (i.e., you cannot hear a signal when the other pair of headphones is unplugged). Again, if we place an oscilloscope probe directly at headphone jacks at the end of our full audio path, we (correctly) do not see a measurable signal on the channel that shouldn't be receiving a signal (a PSD on the signal does not reveal any clear peaks at the signal frequency), so it seems that the issue has something to do with the interaction between our headphones and the Bela.
My code for sending out audio on one channel is below, if that helps.
Your input on what the source of this problem might be is greatly appreciated!
for(unsigned int channel = 0; channel < context->audioOutChannels; channel++) {
if(channel==1){
audioWrite(context, n, channel, 0);
} else {
audioWrite(context, n, channel, out);
}
}