How to know that an AUSampler is playing?

Question

Any way to know if an AUSampler contained in an AUGraph is producing any sound ? Thanks !

Answer 1

1. If you can hear the output
2. If you attach a render callback and can see the audio data is not all 0's
3. If you run the output of the sampler into a mixer unit and turn on volume metering and have a volume level