SynthMaker

Zombie pitch detector

Archive · 2011 2 old posts

From the original SynthMaker forum (2004–2014), with its members’ names and dates.

lesobrod ·

The process of frequency and/or pitch detection of human is very complex and interesting. It includes many areas of nature - math, chemistry, physics, acoustic and psychology.

Here a simple, primitive model of human pitch detection. It based on some conception that for freq "calculation" most important are zeroes (or middle level crossing, if there is DC) of air pressure vibrations.

This model has another " artificall intellect" features (thats why I call it "Zombie")))) - Parallel data processing - Averaging and rounding accordingly to sensitivity of ears and brain - Model of "making solution" about pitch presence (I can't post here detailed info. If someone will be interested, please send a PM.)

Left side of GUI is auxiliary - ranges of meters, rounding of values and update of data freq. Central part include 3 detectors - two about pitch (by pure "Pure" and averaging "Mean" signal ) and one about LFO (tremolo, vibrato) that is very significant part of psychoacoustics. "Pure" detector (in almost all cases) find the most strong harmonic; "Mean" - the lowest harmonic. When the frequency of succefull "zeroes" is stable, the signal identify as "pitched" and freq displaying using bold orange font. Also there is a DC detector.

Right side has knobs for the next parameters: Latency. "Mean" signal are smoothed by this number of samples. Pitch gate. From which degree of uncertainty signal classified as pitch. LFO gate. Relative level of extra-low vibrations that recognized as significant LFO envelope. Noise gate. Relative total signal volume that recognized as significant.

Mode switcher has two positions. With "1", all succefull frequency values are displaying; with "2", only pitch values will be shown. Please note that I don't use in this detector any musical pitch or notes correspondence. There are many scales and theories about tonality, tone ranges etc. They are all about higher intellect activity and products of some historical compromises, and "Zombie" is a biological detector modell. Anyone could easy add (standard or not) note scale corresponding to this osm.

"Zombie" was tested on SM oscillators, WAV files and external microphone and showed good but in some way unstable results.

So I will be very glad to see anyone's opinions, tests conclusions (and no system crash' logs please!) 😈

Dell ·

It performs well. I will find better use of it on the sound reinforcement side than the recording/mastering side.

What is the starting point of the frequency that triggers the DC LED indicator?

Possibly it is detecting a specific dB level for it appears to trigger around 9 Hertz whereas DC is 1 Hz and below.

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