Spectrogram Interpretation

A spectrogram is a visual way of representing the signal strength, or “loudness”, of a signal over time at various frequencies present in a particular waveform. Not only can one see whether there is more or less energy at, for example, 2 Hz vs 10 Hz, but one can also see how energy levels vary over time.

1. What do the colors mean on a spectrogram?
2. What is sound spectrogram used for?
3. What do the black lines on a spectrogram represent?
4. What does intensity mean on a spectrogram?

What do the colors mean on a spectrogram?

Colors in a Spectrogram

With spectrogram displays, colors indicate vertical displacement. Different colors represent different y-axis values. The color bar at the left side of the display indicates the color scheme used.

What is sound spectrogram used for?

Spectrograms map out sound in a similar way to a musical score, only mapping frequency rather than musical notes. Seeing frequency energy distributed over time in this way allows us to clearly distinguish each of the sound elements in a recording, and their harmonic structure.

What do the black lines on a spectrogram represent?

When we see dark lines in a spectrum, they correspond to certain wavelengths being missing due to absorption by matter (in the form of atoms/molecules) on their way. So the dark line represents "absence of light" in a spectrum, not any particular wavelength (color) of light.

What does intensity mean on a spectrogram?

A spectrogram is a graphic representation of the components (harmonics or formants) of a sound as they vary in frequency and intensity over time. Frequency is shown on the vertical axis; time is shown on the horizontal axis, and intensity as relative darkness of the image.