RealTerm is a useful, free, terminal program that can capture a serial input and display it in ASCII, or as a readable number if the word length is fixed or if there's an identifiable header.

As for aliasing, if there isn't a hairy antialiasing filter in the accelerometer, you're stuffed as it's already sampled by the time you get it. But it might not be a problem- I don't know much about it, but I'd expect higher- frequency sounds to couple poorly into the ground. In any case, if the higher frequencies contain information, the aliased signal is really as good as the original, as what you're loking for is a characteristic response.

There was a technique sometimes used in archaeology before resistometers, magnetometers and GPR became popular, that involved banging on the ground with one pickaxe while listening to the response with your ear on the end of another handle held against the ground. It wasn't dreadfully successful unless there were big cavities below ground.

If landmines are involved, please instruct the tuba player NOT to march, otherwise detection by another method could occur.