Strange Audio Distortion When Using Bluetooth Audio in My Car

**rosshaden** · February 17th, 2025 02:55 PM

Hello

I've been experiencing a weird audio distortion issue when using Bluetooth to stream music from my phone to my head unit. The sound is fine when connected via USB or AUX; but once I switch to Bluetooth, there's a noticeable crackling sound; especially during high-volume tracks or bass-heavy music. ItÂ’s not the speakers themselves because they work perfectly on other sources.

IÂ’ve already tried unpairing and repairing my phone, checking the Bluetooth settings & ensuring my head unitÂ’s firmware is up to date, but the distortion persists. I also tried a different phone and it didnÂ’t solve the issue. Is this a known problem with Bluetooth connectivity in car audio systems, or could it be something related to interference, head unit settings, or wiring?

I have checked https://www.tsikot.com/forums/car-audio-video-systems-153-cyber security guide for reference .

Any tips or advice on troubleshooting this would be appreciated. IÂ’d love to get this fixed without having to resort to using a wired connection. Thanks in advance!

Thank you !

**cityfolk** · February 18th, 2025 08:42 AM

Have you tried moving your phone around to different locations inside your car's cabin? Signal might be getting blocked or there might be a source of rf interference within the cabin.

**oj88** · February 18th, 2025 09:46 AM

Low quality DAC on the head unit and/or the two devices can't negotiate a higher codec (ie. aptX, etc.) and just defaults to SBC.

**Dr.Kamiya** · February 18th, 2025 03:29 PM

Originally Posted by oj88

Low quality DAC on the head unit and/or the two devices can't negotiate a higher codec (ie. aptX, etc.) and just defaults to SBC.

Could be the opposite. Device connected via aptX but the signal isn't good enough to maintain the connection, so it's occasionally dropping out.
On the Sony Headphone Connect/Sound Connect App if you choose "Prioritize stable connection" it will use SBC. If you choose "Prioritize sound quality" it'll use aptX, AAC or whichever is your best available codec.
The app specifically says use Stable Connection/SBC if the sound is cutting out.

Either way if you can change codec it's worth trying.

**oj88** · February 18th, 2025 05:40 PM

Originally Posted by Dr.Kamiya

Could be the opposite. Device connected via aptX but the signal isn't good enough to maintain the connection, so it's occasionally dropping out.

The way the issue was described....

...noticeable crackling sound; especially during high-volume tracks or bass-heavy music.

I don't think those are characteristics of RF drop-outs. Sounds more like over-modulation and/or audio clipping. If the problem is not on the codec, it could be a signal mismatch on the analog interface between the Bluetooth module and the amplifier inside the radio.

**Dr.Kamiya** · February 19th, 2025 12:44 AM

Originally Posted by oj88

The way the issue was described....

I don't think those are characteristics of RF drop-outs. Sounds more like over-modulation and/or audio clipping. If the problem is not on the codec, it could be a signal mismatch on the analog interface between the Bluetooth module and the amplifier inside the radio.

Good point, if it was drop outs then it would be happening no matter what kind of music was playing. If only loud or bass-heavy stuff causes it the analog output from the BT module might be triggering some kind of clipping protection circuit in the amp.

**rosie87** · February 25th, 2025 02:55 AM

It looks like a Bluetooth codec or interference problem.
Try to force the SBC or AAC codec in the developer options of your phone.
Also check if your car stereo has a "high quality audio" mode that can be activated.
If the problem persists, test with another Bluetooth device to see if it is the source or the receiver.
Keep us posted if it changes anything!

^_Tutuapp