Spectrogram log(f) ViewĬhoosing Spectrogram log(f) from the Track Dropdown menu will display a logarithmic vertical scale. Note that this is still at a window size of 2048. In the case of this particular test track we can get even better frequency resolution by changing the Window Type to Blackman-HarrisĬhanging to a rectangular window causes the track to be redrawn faster at the expense of very bad frequency smearing. You can zoom in on the vertical (frequency) axis.Īfter zooming in, the vertical ruler changes to allow greater precision of the scale. Looking at the first 0.04 seconds of the track, we can see the the "time smearing" has increased with a window size of 2048 compared to 256. Note that the "spikes" every two seconds are the result of the discontinuities created when joining the segments of tone at different levels. That is, there is much less "frequency smearing" with the larger window size. We can see that the frequency resolution has increased. The image below shows the time smearing at the start of the track.Ĭhanging the Window Size to 2048 and displaying the entire track results in this view of the track. When using the default window size of 256 the spectrogram is drawn quickly, but the frequency resolution is not so good. There is an inherent trade-off between frequency resolution and time resolution. Spectrogram view uses the Fast Fourier Transform (FFT) to display the frequency information versus time. If this is a pure tone, why does the spectrogram show energy at frequencies between 0 Hz and 5000 Hz? levels from -100 dB to -80 dB transition from light blue to dark blue (the tone at -90 dB in the image above is light blue).levels from -80 dB to -60 dB transition from dark blue to magenta (the tone at -70 dB in the image above is bluish purple).levels from -60 dB to -40 dB transition from magenta to red (the tone at -50 dB in the image above is magenta).levels from -40 dB to -20 dB transition from red to white (the tone at -30 dB in the image above is light red). ![]() anything above -20 dB is indistinguishably white (the tone at -10 dB in the image above is white).With the default settings of Gain = 20 dB and Range = 80 dB, the colors correspond to the following levels: The Range setting determines the spacing between colors. There are six color bands in spectrogram view: white, red, magenta, dark blue, light blue and grey. Similarly the "lower" level bands will also "get brighter". With the default setting of 20 dB, any frequency band that originally had (before amplification) a level of -20 dB or greater (and now, after amplification has a level greater than 0 dB) will be displayed as white. It does this by amplifying the signal by the indicated amount. Gain can be said to increase the "brightness" of the display. What do these settings mean and how to they relate to what you see on the screen?Īs you can clearly see, the minimum and maximum frequency settings determine the minimum and maximum frequencies displayed, as indicated in the track vertical scale. This is how the track appears in spectrogram view, using the default settings. This is how the track appears in waveform view. ![]() ![]() The first segment is at a level of -10 dB, the second at -30 dB, and subsequent segments at -50 dB, -70 dB and -90 dB. It consists of five segments of a sine wave tone at 2000 Hz, each 2 seconds long. To demonstrate how the various settings affect the appearance of an audio track in spectrogram view, we will start with this artificially constructed test track. Here is the same recording in spectrogram view: Here is a stereo music recording in waveform view: Spectral selection is used with special Spectral edit effects to make changes to the frequency content of the selected audio.Ĭomparing Waveform View to Spectrogram View A spectral selection is a boxed vertical selection of frequencies within the horizontal time selection. Spectral Selection is active whenever you are in Spectrogram or Spectrogram log(f) view.
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