You can now vary the window length in the spectrogram settings and see how the thickness of the lines varies. The spectrogram will show a horizontal black line. by typing 1/2 * sin (2*pi*1000*x) as the formula, then click View & Edit.
To see how the window length influences the bandwidth, first create a 1000-Hz sine wave with Create Sound from formula. Thus, if the highest peak in the spectrogram has a height of 30 dB/Hz, and the dynamic range is 50 dB (which is the standard value), then values below -20 dB/Hz will be drawn in white, and values between -20 dB/Hz and 30 dB/Hz will be drawn in various shades of grey. Values in-between have appropriate shades of grey. The other window shapes give slightly different values.Īll values that are more than Dynamic range dB below the maximum (perhaps after dynamic compression, see Advanced spectrogram settings.) will be drawn in white. To get a “broad-band” spectrogram (bandwidth 260 Hz), keep the standard window length of 5 ms to get a “narrow-band” spectrogram (bandwidth 43 Hz), set it to 30 ms (0.03 seconds). For a Gaussian window, the -3 dB bandwidth is 2*sqrt(6*ln(2))/(π* Window length), or 1.2982804 / Window length. the width of the horizontal line in the spectrogram of a pure sine wave (see below). The window length determines the bandwidth of the spectral analysis, i.e. If this is 0.005 seconds (the standard), Praat uses for each frame the part of the sound that lies between 0.0025 seconds before and 0.0025 seconds after the centre of that frame (for Gaussian windows, Praat actually uses a bit more than that). You can see this if you record a Sound at 44100 Hz and set the view range from 0 Hz to 25000 Hz. If this maximum frequency is higher than the Nyquist frequency of the Sound (which is half its sampling frequency), some values in the spectrogram will be zero, and the higher frequencies will be drawn in white. The standard is 0 Hz at the bottom and 5000 Hz at the top.
All these settings have standard values ("factory settings"), which appear when you click Standards. These settings will be remembered across Praat sessions. from the Spectrogram menu, you can determine how the spectrogram is computed and how it is displayed.
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