Open Radar

 
Summary:
An iPhone running iOS9.1 and using Voice Over sometimes stops correctly outputting and instead outputs low rumbling noises and hisses. It happens 'sometimes', but multiple times per day, rendering the iPhone completely useseless for a blind person.

Steps to Reproduce:
Use iPhone with iOS9.1 and Dutch Voice Over.

Expected Results:
Voice Over should always be understandable, not random noise.

Actual Results:
Voice Over sometimes doesn't work, just outputting random noise.

Regression:

Notes:
This isn't happening on my iPhone, but on my brother's iPhone, he's blind so the iPhone is literally his world. When it works it's great, Voice Over was leagues beyond what the rest of the world produced on mobiles. When it doesn't work it's arguably the most frustrating experience he has to endure.

I've tried to see if he could find some steps to reproduce the bug reliably, but so far no luck. This was happening on an iPhone 5S, we tried making a backup, completely erasin the device and then restoring from the iCloud backup, alas no luck.

We tried buying him a new iPhone 6S, restoring it from iCloud backup, the bug happened on that phone as well. I've suggested changing the Voice he uses, this sees tp have some effect, but at random times Voice Over still stops working.

Is there a way I can help you find out what is causing this?