The Program should be mainly self explainatory. There is a wave-view labeled in milliseconds, to the right there are two LCD-Displays one showing the actual frequancy, the other one showing the frequancy of the nearest note. Below these there are three parameter boxes for sampling frequency, sample number, and trigger level.
The sampling frequency affects the number of measurements per time.
The samplenumber affects the accuracy of the measurements.
The triggerlevel affects the reliability. (different settings are good for different waveforms)
Below the wave-view there is a note-scale with a pointer which shows the actual frequency. The note scale is lableled in Hz for several octaves and has a subinterval tiling of 10 cent.
In the options menu one can adjust the tuning and the note scale.
Normal | A = 440.0 Hz |
Wien | A = 435.0 Hz |
Physical | C = 16.0 Hz => A = 430.5 Hz |
Equidistant | Normal tuning |
Natural | Tuning by overtones |
For natural tuning the base tone has to be adjusted. This is done by simply clicking at the proper note on the note-scale.
US | A,Bb,B,C,Db,D,Eb,E,F,Gb,G,Ab |
US-Alternate | A,A#,B,C,C#,D,D#,E,F,F#,G,G# |
German | A,B,H,C,Db,D,Eb,E,F,Gb,G,Ab |
German-Alternate | A,B,H,C,C#,D,D#,E,F,F#,G,G# |
The accuracy of the frequency measurement depends only on the sample number. A rule of thumb is:
10000 accuracy[cent] = ---------------- 6*samplenumber
So you can get the saplenumber for a certain accuracy by:
10000 samplenumber = ------------------ 6*accuracy[cent]
( 1 cent = 1/100 of a halftone step )
The accuracy for a samplenumber of 1024 gives 10000/(6*1024) cent = 1.62 cent
However there is also a systematical error (bug) in my program which can result in a shift of all frequencies by some cent.
For more information check out the next page.