Am a bit out of my depth here, not familiar with any of the tools being used. Not sure where else to look for anything audible besides /etc/audisomething
https://i.imgur.com/SHhU2A8.png
Also found /etc/audio/volume which has sinks defined for speakers(?) and headphone(not BT?), which might be just a red herring.
[root@kindle audio]# cat volume
# The number of possible sinks
Sinks = 2
# Sink 1
sink = speaker
size = 16
1 = 256 1.0
2 = 325 1.0
3 = 332 1.0
4 = 338 1.0
5 = 343 1.0
6 = 347 1.0
7 = 350 1.0
8 = 353 1.0
9 = 356 1.0
10 = 359 1.0
11 = 362 1.0
12 = 365 1.0
13 = 368 1.0
14 = 371 1.0
15 = 374 1.0
16 = 377 1.0
# Sink 2
sink = headphone
size = 16
1 = 256 1.0
2 = 319 1.0
3 = 326 1.0
4 = 332 1.0
5 = 337 1.0
6 = 341 1.0
7 = 344 1.0
8 = 347 1.0
9 = 350 1.0
10 = 353 1.0
11 = 356 1.0
12 = 359 1.0
13 = 362 1.0
14 = 365 1.0
15 = 368 1.0
16 = 371 1.0