Midicode Oscilloscope Support

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Oscilloscope
Synthesizer

Midicode Oscilloscope Analyser Support Page

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How can I get smaller frequency bins on the analyser trace?
Why does Actual time base indicate a time which is different from the time I select?
What do the Window modes Hanning, Hamming, etc. mean?
How can I access help from within the program?
Can I always see all of the frequency analyser bins?
How do I know the frequency of a partial in the analyser display?
What are meant by the terms 'time domain' and 'frequency domain'?
How does Midicode Oscilloscope Analyser produce the frequency display?
What do the height of the frequency analyser lines mean?
I am looking at a single frequency signal but the energy is distributed amongst several frequency bins. Why is this?
How do I get rid of clicks from a sample loop?
Can I write a text file with just the frequency domain data?

Q	How can I get smaller frequency bins on the analyser trace?
A	Select a longer time base. The frequency bin width is the reciprocal of the time base. Frequency bin width indicated on the Frequency tab is the same as Equivalent frequency indicated on the Time tab.

Q	Why does Actual time base indicate a time which is different from the time I select?
A	The time base needs to be an integral number of samples. The number of samples closest to the time base you select will be chosen and the actual time base will be displayed. There is less likely to be a difference if you choose an integral sampling rate on the Options tab, i.e. 24 kHz, 48 kHz or 96 kHz.

Q	What do the Window modes Hanning, Hamming, etc. mean?
A	An input signal is not necessarily periodic in the time base buffer period. Consequently the effect of the 'window' of the input buffer is superimposed on the signal. The various 'window functions' seek to reduce this effect. For more information about window functions please follow the links on the links page.

Q	How can I access help from within the program?
A	Click on the question mark button near the top right of the window. There is extensive illustrated help available with the program.

Q	Can I always see all of the frequency analyser bins?
A	Usually several frequency bins are drawn per display line so that the entire frequency range can be shown across the viewing pane. The magnitude of the largest bin is shown. The number of bins per line is shown on the Frequency tab. Use the Zoom control to zoom in on the display so there are less bins per line. Pan across all the available bins using the View control.

Q	How do I know the frequency of a partial in the analyser display?
A	Point to the line. A pop up hint will appear giving the lower bound of the lowest frequency bin for that display line.

Q	What are meant by the terms 'time domain' and 'frequency domain'?
A	The oscilloscope style display of an input signal is know as the time domain representation as it shows how the signal varies with time. The spectrum analysis of this signal is known as the frequency domain representation as it shows the relative strengths of the frequency partials present in the signal.

Q	How does Midicode Oscilloscope Analyser produce the frequency display?
A	The program uses a discrete Fourier Transform. According to Fourier Theory any periodic waveform can be represented as a set of harmonically related partials (cosines and sines) of differing amplitudes. The cosines and sines can be taken together to represent the magnitude and phase of these partials. For more information on Fourier theory follow the links from the links page.

Q	What do the height of the frequency analyser lines mean?
A	They show the relative strength of the partials on the logarithmic decibel scale. If the input is 16 bit then the maximum amplitude of any partial is 96 dB. If the mode is set to Magnitude then each line may be up to 8 grid squares high or 12 dB per grid square.

Q	I am looking at a single frequency signal but the energy is distributed amongst several frequency bins. Why is this?
A	The frequency of the input signal does not match the frequency bands of the analyser. Try adjusting the Time base fine control to get a better match.

Q	How do I get rid of clicks from a sample loop?
A	Use the Find zero start and Find zero end controls to remove sharp transitions from your loop.

Q	Can I write a text file with just the frequency domain data?
A	Yes. Use controls on the View tab to hide the time domain traces then write the file.

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Oscilloscope
Synthesizer

January 2010