Put it at the very start of a voice-command moment, followed by the spoken line and then a reaction sound. If the command is misunderstood, follow it with the Classic Error Sound; if the answer is correct, close with the Bell Ding Sound for a clear finish.
About this sound
This is the very short electronic cue, lasting under a third of a second, that plays when Google voice search begins listening for a spoken query. Its light, rising tone feels alert and expectant, like a device pausing to pay attention, and it works as a quick signal that the microphone is ready.