Page "Pitch detection algorithm" Paragraph 3

One simple approach would be to measure the distance between zero crossing points of the signal ( i. e. the Zero-crossing rate ).

However, this does not work well with complex waveforms which are composed of multiple sine waves with differing periods.

Nevertheless, there are cases in which zero-crossing can be a useful measure, e. g. in some speech applications where a single source is assumed.

The algorithm's simplicity makes it " cheap " to implement.