Quality of audio output changes when starting a new window

Has anybody else experienced a similar problem? Or can you help me trouble shoot this issue please? I'm busy playing audio in a tab of the browser. The sound quality is good (rich, full, deep). Next, I open a new window by any means (Ctrl+N / Open link in new window / Menu > New window) As the new window appears, the current audio playback becomes tinny / lower quality. After a 3 seconds, the normal good sound quality starts again. I'm currently using Bluetooth connected headphones and this happens on different headphones. I have to find some wired headphones first before I can try that. This happens with every new window that I open, regardless of the number of open tabs in current windows or how many previous open windows I already have. This happens regadless if audio enhancements of the output device are enabled or not. Spatial sound is set to off. Windows is set to 'do nothing' & will not adjust the volumes of different sounds when I'm using my PC to place or receive telephone calls. OS: Windows 11 with latest patches Firefox: latest & older builds Hardware drivers: All manufacturer drivers applied PS I can replicate this issue by changing between the 'Playback' & 'Recording' tab in the Sound Control Panel applet. That is to say, the same decrease in audio quality happens when I change from the Playback tab to the Recording tab. Audio quality improves again when I change from the Recording tab to the Playback tab https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2026-09-12-15-38-23-1accad.png PPS My new windows are set to open on 'about:support' PPPS Can't reply to previously archived question : https://support.mozilla.org/en-US/questions/1525613