Subject: how to detect occurrence of standing wave by microphone in kundt tube

the kundt tube is well known for calculating speed of sound. I want with the 
same setup, but with tube of unknown (finite) length, to determine tube's length
with speed known and the frequency a parameter. this means I need to detect the 
occurrence of standing wave. The measurement (by microphone) would happen at 
the point where the speaker is. If the mic is connected to oscilloscope, can 
you tell a standing wave from non-standing wave and hence determine length of 
tube ? I would guess the mic would record zero signal because all is cancelling 
out in a node of standing wave. is this correct ?

reason I ask : I want to do this in water, and use a slowly varying "chirp" to 
determine distance of objects in the water from their echo up to 2 meters 
distant. this could be built into remote control submarine (see 
www.subcommittee.com and check who is the mad scientist here ;-)

Regards,
Ronald van Aalst  

Re: how to detect occurrence of standing wave by microphone in kundt tube