-1

In class the lecturer asked us a question, during a concert the conductor hears a false note (noise), translating this into signal fundamentals how does the conductor detect this noise?

My guess is that it may be related to the Fourier transform, but I'm not sure I'm even close to the answer.

maofyn
  • 1
  • 1
    This is not a question about programming, and therefore does not belong on Stack Overflow. [Signal Processing Stack Exchange](https://dsp.stackexchange.com) is a more suitable place for your question. – Cris Luengo Sep 06 '22 at 15:11

1 Answers1

2

Check out a spectrogram. it's a 3d representation of a frequency domain over a time. As a general routine:

  1. divide your time-domain recording of a musical piece into suitably sized time segments, small enough that they can capture the shortest musical note you want to represent (preferably smaller than this amount as you want more granular measurements of when the note starts/stops).
  2. take the Fourier transform of each time segment, and represent this information in a spectrogram (X-axis for time, Y-axis for frequency, and Z-axis (colour) for signal power).
  3. do appropriate filtering on each time segment to keep only frequencies with significant signal power.
  4. compare this against your sheet music. Sheet music is essentially a spectrogram, telling you which notes(frequencies) should be played at which times (using the BPM or time signature of the music). if you have a note present in the spectrogram but not in the sheet music, it's spurious or accidental (or the result of a badly formed spectrogram).
Raphael Treccani-Chinelli
  • 66
  • 6