S Max Parking Sensor tone

[Elizabeth]

Hello, I hope someone can assist with an S Max parking sensor query. My parking sensors have very occasionally changed tone sound but have always reverted to the normal tone relatively quickly. For the past 4 or 5 days, the tone sound has been different (both the way it sounds and volume). Any idea why this is happening and how I can get them back to normal? Thanks!  

[Meta55]

Mines has done that once, sounded like the speaker was blown. It’s never done it again. 

[Elizabeth]

Thank you. It's done it before and reverted which is why I'm hoping it's something that can easily be fixed 😬

[tomtom70]

This is probably the fallback to instrument cluster "speaker" rather than the better audio quality provided by the chimes and beeps played through the stereo. A low battery may be the cause.

[DaSingh]

When the battery voltage is lower it doesn't use the Speakers. 

This happens to mine if its sat on the drive for awhile.