MFCC (Mel-Frequency Cepstral Coefficients) magnitude reveals key audio characteristics:

Magnitude Insights indicate:

• Spectral envelope shape
• Energy distribution across frequencies
• Speech/sound timbre
• Phonetic information
• Noise levels

Magnitude Range:

• Typically normalized between -1 and 1
• First few coefficients (0–3) contain most significant information
• Lower coefficients represent overall spectral shape
• Higher coefficients capture fine details

This image shows two related visualizations of Mel-Frequency Cepstral Coefficients (MFCCs) extracted from an audio signal. Let’s break down each plot and what the magnitudes tell us:

Left Plot: MFCC Coefficients (Heatmap)

• X-axis: Time (in some unit, likely seconds or frames). This represents the progression of the audio signal.
• Y-axis: MFCC Coefficients. Each row corresponds to a different MFCC (MFCC 0, MFCC 1, MFCC 2, etc.).
• Color (Magnitude): The color in each cell represents the magnitude or amplitude of the corresponding MFCC at a specific time. The colorbar on the right indicates the dB (decibel) scale, showing the range from -400 dB (dark blue) to +200 dB (dark red). Red colors indicate higher magnitudes (more energy), while blue colors indicate lower magnitudes (less energy).

What the Heatmap Tells Us:

• Temporal Dynamics: The changes in color across the x-axis (time) show how the MFCCs evolve over the duration of the audio. This reflects changes in the spectral characteristics of the sound.
• Coefficient Importance: The different rows show the relative importance of different MFCCs. Some MFCCs might consistently have higher magnitudes (more red/orange), indicating they carry more information about the sound.
• Feature Patterns: Looking for patterns in the colors across time and MFCCs can reveal characteristics of the audio, which might correspond to specific sounds or phonetic events.