What is an "impulse sound" ?

Question

I was listening to a classical station as I was drifting in and out of sleep and I heard the broadcaster talking about impulse sounds which "contain all frequencies in them" and for this reason were used in various composers' music. He said that an example of an impluse sound is a very large balloon popping. This is fascinating to me but I wish I had a better understanding of what these things are and why. Anybody know? I looked it up and could find nothing.

Answer 1

An impulse is a zero-duration pulse that contains finite energy (and thus is of undefined amplitude). Being of zero duration, it theoretically contains energy at every imaginable frequency.

Obviously it is a mathematical concept and can only be approximated in real signals such as an electric or sound wave. A zero-size, nonzero-energy explosion would generate an impulse.

A very large balloon popping is not a good example, since this is of relatively long duration, at least the time sound takes to travel the diameter of the balloon. A cap gun, or the slat or whip occasionally found in classical scores, comes closer.