Sound failure on iPad Air 2?

Just wondering if anyone else has experienced this. I recieved my ipad earlier in the week all working fine, using various apps playing music happily.

This morning when i went to watch a video on youtube it wouldn't play with sound...(obviously the volume was up and not in mute mode)

When i held down the button to bring SIRI up, a loud buzz came from the speakers, the same happens when i turn on the lock screen sounds.

I haven't gone to the extent of resetting everything back to factory defaults yet.

any help much appreciated!!