Introduction to Reading a Spectrogram

By Jeremy Fisher

When reading a spectrogram, you are usually presented with two screens. The upper screen displays the sound signal and the lower screen displays the particular type of analysis you are using.

To see/download a larger version of the illustrations in this article click on the images below. Enlargements open in a new window.

When you input a sound, either by loading a pre-existing sound, or using a microphone, the inputted sound appears on the upper screen.

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This example shows the sound EE (/i/) repeated three times. On real-time input, you can check the volume of your vocalising, and change the settings, move the microphone, or speak/sing softer our louder as appropriate. Time (in seconds) is show across the page and volume (amplitude) is shown going up the page. On this programme (MultiSpeech from Kay Elemetrics), the signal colour on input changes from green to yellow to red, depending on whether your vocalising is overloading your soundcard.

On the lower screen, the information going up the page changes depending on what you want to study. On a Spectrographic screen, the harmonics in each sound are shown.

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The pitch (Frequency in Hz) is shown going up the page, and strength of signal is shown by how black each area is the stronger the signal, the blacker the harmonic. A white area within a signal means those harmonics are missing or too weak to be read. The spectrographic screen can be used to discover a great deal of information including fold mass activity, the relationship between phonation and airflow, and activity of the false vocal folds.

On a Formant screen, the position of the formants in each sound is shown.

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Formants are clusters of harmonics that are stronger than the surrounding areas. In spoken or sung examples, formant readings are used to identify vowels and also the relationship between laryngeal height and the tongue.

A Formant screen may be overlaid onto a spectrographic screen.

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Most of the examples on this site show spectrographic information (in black and white) and formant analysis (in red).