Is it possible to play a sound so briefly, during such a short period of time, that it isn't noticed by humans?
I have the idea to use sound for distance measurements. This is common with ultrasound, but I want to do it with common smartphones and thus in the ordinary audible frequences they are capable of generating and detecting. Ultrasound is prefered because it doesn't disturb people, so I wonder if audible frequences could be made inaudible by being brief.
If I make a phone generate a tone during only a millisecond once every five seconds, would it be perceived?