The WebAudio test is not the only measurement in these scripts. Inspection of the bundles found code that queries or measures:

• canvas rendering and toDataURL()
• WebGL renderer information, extensions, and shader precision
• audio oscillator and analyser output
• screen and viewport dimensions
• device pixel ratio
• hardware concurrency and device memory
• installed browser plugins
• supported audio and video formats
• WebRTC behaviour
• browser performance timing
• mouse, touch, focus, and scroll events
• device motion and orientation
• properties commonly associated with browser automation

There is also code for serialising and encrypting results, making requests to Alibaba telemetry services, and sending data with fetch() or sendBeacon().

Not sure you need all this to play audio.

If that's actually their problem, they could easily just play a small amount of silence before a video's content. They don't need to be constantly tying up an audio stream.

Audio fingerprinting works because small differences in browser versions, operating systems, audio libraries, and hardware can produce slightly different results from the same generated signal. It is not necessarily enough to uniquely identify a device by itself, but it becomes much more useful when combined with canvas, WebGL, hardware, timing, and interaction data.

The gaining happens after retrieval of the results it seems: so it's just silent for the end user. And perhaps they do both fingerprinting, and ensure audio devices remain awake.