One of the types of objects in Praat. For tutorial information, see Intro 3. Spectral analysis.
A Spectrogram object represents an acoustic timefrequency representation of a sound: the power spectral density PSD (f, t), expressed in Pa^{2}/Hz. It is sampled into a number of points centred around equally spaced times t_{i} and frequencies f_{j}.
Inside a Spectrogram
With Inspect, you will see the following attributes:

xmin

start time, in seconds.

xmax

end time, in seconds.

nx

the number of times (≥ 1).

dx

time step, in seconds.

x1

the time associated with the first column, in seconds. This will usually be in the range [xmin, xmax]. The time associated with the last column (i.e., x1 + (nx – 1) dx)) will also usually be in that range.

ymin

lowest frequency, in Hertz. Normally 0.

ymax

highest frequency, in Hertz.

ny

the number of frequencies (≥ 1).

dy

frequency step, in Hertz.

y1

the frequency associated with the first row, in Hertz. Usually dy / 2. The frequency associated with the last row (i.e., y1 + (ny – 1) dy)) will often be ymax  dy / 2.

z_{ij}, i = 1 ... ny, j = 1 ... nx

the power spectral density, in Pa^{2}/Hz.
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© ppgb, March 21, 2007