Figure 2.

Spectrogram of a recorded breathing sound. The spectrogram shows the spectro-temporal features of an air intake (left) and output (right) in a single breathing-sound cycle. Frequency-modulated, ultrasonic tonal components can be observed during air intake. These components result from turbulences in the nasal cavity during depression. Note the good signal-to-noise ratio, which was realizable with the recording equipment described in the methods.

Gröger and Wiegrebe BMC Biology 2006 4:18   doi:10.1186/1741-7007-4-18
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