App background "silent" mp3 isn't silent on iOS 18

[r1ch]

I notice that the app plays a strange hissing sound -

• this can be reduced by changing the system volume
• checking the code I see that this plays an mp3
• the mp3 file looks to be entirely silent so I suspect this is an iOS issue sadly

[r1ch]

(and btw - thank you for the great app - I gave 5⭐ on the App store!)