Most likely that is the sound associated with the Screen Lock/Unlock setting

go to Settings/Applications/Sound/Screen Lock Sound

once you find that, uncheck it.

Lots of settings on that page you can turn off if you do't like the noise, such as the keypad, Haptic, etc.... most of mine of OFF

On my phone, it was just a short 'click' or 'tick/tock' noise. I turned it off for the same reason, my wife bitches about any kind of noise.

 

I think I'm having the same problem. I've had the phone a year now and this is a new noise, maybe appeared after a recent software upgrade.
It's like a beep beep that happens when I press the home button to wake the screen from black.
I have tried everything to get rid of it. It only goes if I silent the notifications.
I've tried going into sounds and disabling the screen lock sound, but it's still there.
Currently driving me insane. The most ridiculous and unnecessary sound!
Please help

 

Sorry, have to disagree with you there, the most ridiculous and unnecessary sound has got to be the the stupid click noise when you hit the keys or screen, extremely irritating as well if you are near someone who has the bad manners to have the sound switched on. Phil

 

I've solved the noise my phone was making. Well my flatmate did.
Go to settings => connections => turn the NFC setting off.
No idea what it's for, but that was the source of the noise in my case.
Hope that helps

 

Well, I had already turned NFC off and was not even aware that NFC would make a noise.

I do not have any sound at all from my phone UNLESS a SMS text message comes in, or a phone call is trying to get my attention. I have everything else muted....

My wife can hear a pin drop in the basement and gets mad because it wakes her up. So, the phone went silent the moment it got unwrapped.

 

Thankyou! That sorted my problem - turns out after updating, NFC got turned on and was constantly recognizing my credit card (stored in my mobile wallet).

 

Is it this sound?