Understanding spectrograms

A spectrogram is a time-varying spectral representation that shows how the spectral density of a signal varies with time.

It represents a spectrum of frequencies of the sound or other signal in a visual manner. It is used in various science fields, from sound fingerprinting like voice recognition to radar engineering and seismology.

Usually spectrogram layout is as following: x-axis represents time, y-axis represents frequency, and the third dimension is amplitude of a frequency-time pair, which is color coded. This is three-dimensional data, therefore, we can also create 3D plot where the intensity is represented as height on the z-axis. The problem with 3D charts is that humans are bad at understanding and comparing them. Also, they tend to take more space than 2D charts.

Getting ready

For serious signal processing, we would go into low level details to be able to detect patterns and auto fingerprint certain specific, but for this data visualization recipe we, will...