Change audio playback speed in whatsapp web
Change playback speed from 1 (normal speed) up to 2 (2x faster playback) in 0.25x intervals.
Over the "knob", a right mouse button click will increase and a left mouse button click will decrease playback speed. Each click, your preference is saved to remains as you like next time you access Whatsapp Web.
To apply (o reapply) the playback rate on entering on a chat or loading old audios, just cycle the "knob" (e.g.: 1 click with mouse right button, 1 click with left mouse button).
Simple, as life should be :)