How to stop Firefox page-opening sound?

[rjbull]

Lately Firefox (16.0.2) has been making silly noises each time it opens a Web page.  It didn't used to do this, and I haven't even had any recent updates that I know of.  I badly want this irritating sound turned off, but I can't see where to do it under Options.  Please can someone point me in the right direction?

Thanks...

[Curt]

it is certainly not Firefox itself, doing it. So it must either be an addon, doing it, or your installed security program scanning each Internet page. But I have never before heard of such "sound feature", so I cannot say one or the other.

[rjbull]

Thanks