When I try an audio restoration of music containing trumpets, trombones, or other brass it breaks up. Why?
It turns out that the trumpet waveform is particularly un music-like! Rather than being a mixture of harmonics which is quasi-static, the mixture contains frequencies which are periodically present then absent. A typical waveform is shown below: Each one of the down going spikes has some high frequency content right at the tip, but not elsewhere. This makes the tip look like a “tick” or “click” to the audio click removing software. When this happens, some of the tips are replaced with smoother data like in the figure below: Notice how several of the down going spikes are missing. This makes the trumpet sound broken up. The best solution for this is to remove ticks manually for music containing brass. I am working on algorithms that are more robust with respect to brass. I’d like to know if there is interest in this. It should be noted that Cool Edit Pro has algorithms that look for pulse trains like this and then refuses to consider them as ticks. It works fairly well.
