There are no sounds being played for any mobs, events, noises behind the player.
To test I created a rectangular minecart tract with powered rails to keep it going forever. I stood in the middle and I can correctly hear the cart through the front right and left speakers but it goes silent as it goes behind me. (obviously I'm standing on the ground looking forward in the test, the flying is just to show the setup)

Speakers are 4 speaker surround (windows labeled quadraphonic).
Windows speaker test plays the chimes from all 4 speakers correctly.
Soundcard Creative X-fi
Minecraft Bedrock has no audio settings.

Doing the same thing in Java Edition has sound working correctly.