Understand the Difference Between Amplitude Spectrogram and Magnitude Spectrogram

By | August 30, 2023

Amplitude Spectrogram and Magnitude Spectrogram are two terms we often find in some books. What the difference between them? In this tutorial, we will discuss it.

Amplitude Spectrogram

It represents the magnitude of the complex-valued Short-Time Fourier Transform (STFT) coefficients of an audio signal.  We can compute it by taking the absolute value (or modulus) of the STFT coefficients. The amplitude spectrogram provides information about the distribution of energy or signal strength across different frequencies and time.

In order to get an audio amplitude spectrogram, we can read this tutorial:

Understand Audio Amplitude Spectrogram and Compute it in Python – Python Tutorial

Magnitude Spectrogram

It is similar to the amplitude spectrogram and also represents the magnitude of the STFT coefficients. However, it is often used when the STFT coefficients have been squared or processed in a manner that preserves their non-negative values. In other words, the magnitude spectrogram refers to the squared magnitude or power spectrum of the STFT coefficients.

In practice, amplitude spectrogram and magnitude spectrogram are sometimes used interchangeably. The difference between them may not always be significant. Both of them provide a visual representation of the frequency of the audio signal over time.