Bug 243260 – When a bluetooth headset is attached, the internal mic gain is very low

• Status: NEW
• Component: WebRTC

[Joshua Smith]

In Safari 15.6, the internal mic gets very quiet when a bluetooth headset is attached. I've created this simple test page to demonstrate:

https://kaontest.s3.amazonaws.com/mictest/index.html

It starts with the default mic (showing a level meter and a DB estimate). If you click a button to select a different mic, it will reload the page and use that mic instead.

Test 1:

With no bluetooth headset attached, the levels from the internal mic are strong.

Test 2:

Attach a bluetooth headset and reload the page.
Click the button to select the bluetooth headset.
The levels from the headset mic will be strong.
Click the button to select the internal mic.
The levels from the internal mic barely register.

Notes:

- In a video-conferencing application, you can hear that internal mic works. It is just extremely soft.
- I checked that this isn't a system preferences issue; cranking internal mic gain there does not help.
- Using the same test page in Firefox 103, everything works correctly, so this appears to be a Safari issue, not a Mac OS issue

[Radar WebKit Bug Importer]

<rdar://problem/97707103>

[Joshua Smith]

I am unable to reproduce this in Mac OS 12.4 on an M1 2020 macbook air. So it may be a Mac OS 11-only problem.

[Michalis]

I can replicate this, there is a substantial difference in how the VU meter on the test page behaves when having my Bluetooth headset (Powerbeats Pro) connected and without, always monitoring my MBP Internal Mic (M2 Pro). I have also come across an issue (which I believe to be similar) with Safari in a web-RTC-enabled app where having the BT headset connected but selecting the MBP internal mic produces a distorted sound.