In order to improve the system and make it smaller, there are some alternative implementations that bear further discussion. 


It might be possible to use a single transducer to both send and receive the signal.  This was tested at the onset of the experiment, but rejected due to the fact that a speaker sensitive enough to receive the echo was not readily available.


Another suggested implementation was to use the aircraft noise itself in place of the pulse.  A directional microphone would be used to receive the echo of the aircraft noise from a chosen surface, and an autocorrelation function would be employed to determine the delay.  This implementation was not investigated due to time constraints, but could prove to be a viable solution and is worthy of consideration.