Spectrogram Plot

The spectrogram plot displays a frequency-domain representation of the audio signal. The horizontal axis represents time while the vertical axis represents frequency (measured in Hz, or cycles per second).

The horizontal ruler indicates time as measured from the beginning of the recording in seconds. Longer recordings will show minutes and seconds in MM:SS format, and still longer recordings will show hours, minutes and seconds in HH:MM:SS format.

Different colors are used to represent the relative signal power levels (on a logarithmic scale) for different frequency components. The color bar at the bottom of the spectrogram plot indicates which colors are used to represent the relative power levels as measured in decibels. The choice of colors can be changed by using the Display Controls.

Song Scope can display the frequency plot in one of three different ways as follows:

Linear Scale

The linear scale is displayed when a sound file is first opened and shows the frequency in Hz.

Logarithmic Scale

The logarithmic scale shows the same frequencies as in the linear scale above, but stretches out the range on a log scale such that low frequencies are spread out and high frequencies are closer together. The log scale is more representative of how sound is heard and is used internally by Song Scope when comparing sounds. The log scale can be changed by using the Spectrogram Controls.

Logarithmic Scale with Signal Normalization

The log scale with normalization shows the same frequency scale as above, but the power levels are "normalized" to illustrate how Song Scope will interpret the signal for pattern matching. Song Scope's signal detection algorithms are used to determine if a given time slice contains signal or not. Power levels are only shown for detected signal.

You can move the mouse pointer over the spectrogram plot to view the corresponding time, frequency and relative power levels as shown in the status bar at the bottom of the Song Scope window.

You can also hold down the left mouse button while moving the mouse to view the difference in time and frequency in the status bar. When the left mouse button is released, the time and frequency portion of the signal will be selected.

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