This is an extremely low-budget solution, but you could load the audio into a program that charts the amplitude of the signal over its length, like most audio editors (e.g. Audacity [1])

Then you can visually see spikes [2].

You may be able to use such an editor to remove the ambient noise and see it more clearly as well.

[1] http://www.audacityteam.org/download/

[2] http://manual.audacityteam.org/