## Mel Spectrogram

Mel Spectrogram is a graphic representation of a Sound Wave, visualising frequency over time.

Here is a Mel Spectrogram of the audio of a Trumpet

The process of generating a Mel Spectrogram works like this:

- Break the audio signal down into short frames
- Convert time signal into the frequency domain using a Fourier Transform
- Convert frequencies into Mel scale, to more closely align with our intuition of frequencies. This operation is called Mel Filter Bank.
- Plot the Mel values over time.

## Mel Scale

The Mel Scale is a *perceptual scale* of audio frequencies. In other words, it represents our perceived distance of the frequencies from others.

The Mel scale is a logarithmic formula where 1000Mel = 1kHz. You can convert Hz to Mel using this formula:

$Mel(f) = 2595 \log_{10} (1 + \frac{f}{100})$