The Doppler effect is a real-life sound phenomena that shows up as a frequency change when either you the listener or the source of the audio is moving, its better explained here: Doppler Wiki.
Requires: Mod Menu (in version 1.0 only) | Fabric API
Compatible with Simple Voice Chat and Plasmo Voice.
Showcase
https://www.youtube.com/watch?v=dTkfkTWfMPQ
Config
Default effect "scale" is at 40%, noticeable but not too exaggerated, though I havent tested all means of movement next to audio sources, so you're free to change it in ModMenu's settings screen for the mod or in the config file located at <minecraft>/config/doppler.cfg (value is a decimal with ranges from 0-1 (default: 0.4), though no hard limits).
The Doppler Team
