[eightoeight]

I hear these sounds when using Safari, not on most webpages, but on certain webpages like Apple's Support login page I notice it...

[slow moe]

There were threads a while back where some people heard high pitched noises coming from their PB's while viewing a secure web page in Safari, but I could never hear what they were talking about.

[ElBerserko]

I can hear it on my new aluminum 15inch. It only happens when you visit secure sites (https) and it is fine with IE. I also noticed that I get the same noise sometimes when using First Class Client 7.101, but slightly less loud as in Safari.