What are the quality assessment metrics for audio generation (FAD, MOS)?

Audio generation quality is often evaluated using the following metrics:

• FAD (Fréchet Audio Distance) — a metric similar to FID in images. It measures the distance between the feature distributions of real and generated audio, obtained using a pre-trained model (e.g., VGGish). The lower the FAD, the closer the generated audio is to real in perception.

• MOS (Mean Opinion Score) — a subjective assessment of audio quality based on listener surveys. Typically, people rate audio on a scale from 1 to 5, where 5 is the best quality. MOS is considered the gold standard but requires effort and cost to conduct surveys.

In practice, objective metrics (FAD) are often combined with subjective ones (MOS) to obtain a more comprehensive understanding of audio quality.