# Understand Frame Rate of the Mel-spectrogram in Audio – Librosa Tutorial

By | March 5, 2022

In this tutorial, we will introduce how to compute the frame rate of the mel-spectrogram using python librosa.

You may find this description in some papers:

In our implementation, the frame rate of the mel-spectrogram is 62.5 Hz and the sampling rate of speech waveform is 16 kHz

This sentence contains two questions:

• 1.How to compute the sampling rate of an audio?
• 2.How to compute the frame rate of the mel-spectrogram?

Here we will answer these two question one by one.

## How to compute the sampling rate of an audio?

It is easy to get the sampling rate of an audio. Here is the tutorial:

View Audio Sample Rate, Data Format PCM or ALAW Using ffprobe – Python Tutorial

Meanwhile, we also can use librosa.load() to read audio data using a customized sampling rate.

Understand librosa.load() is Between -1.0 and 1.0 – Librosa Tutorial

## How to compute the frame rate of the mel-spectrogram?

In order to compute mel-spectrogram, we can use librosa.feature.melspectrogram(). Here is the tutorial:

Compute and Display Audio Mel-spectrogram in Python – Python Tutorial

The key parameter is: hop_length

We can use formula below to compute the frame rate of the mel-spectrogram.

frame_rate = sample_rate/hop_length

For example: frame_rate = 62.5, sampling rate = 16 kHz

hop_length = 16000 / 62.5 = 256

It means we will set hop_length = 256 when using librosa.feature.melspectrogram().