Essentially, broadcasting static during a call on is a sign of the fact that signal power is degrading (or that there’s no sound coming through in any way). When signal power degrades sufficiently, the static sound emerges.
When there’s no communication coming through, it is a complete different story. A walkie talkie has what’s acknowledged as a ‘squelch’ monitor circuit that keeps tabs on the signal power. The squelch circuit will mute the amplifier as soon as it realizes that there’s no signal coming through into the radio. This is, fundamentally, a similar function as your Television has when it cuts off an unavailable channel after a set time. However, in the moments before your two way radio ‘squelches’ the signal, you will hear static, or ‘white noise’ as it is also known as.
‘Squelching’ is a fairly vital a part of any/all broadcasting gear. The method utilised in your walkie talkie is called a ‘carrier squelch’ and is more than likely to be manually changeable.
From Wikipedia (as of 17/5/13):
So what exactly is ‘white noise?’ In accordance to Joe Shambro, writing for About.com’s guide to household recording,
“White noise is a static sound that has equal energy on every frequency. Think about this for a second: every frequency from 20Hz to 20kHz is equally represented at the same velocity; this type of frequency scale is called a “linear” scale. This gives the noise a uniform, static sound that the human ear detects as somewhat harsh and heavy-handed toward the high frequencies. However, white noise represents a very unnatural way of presenting frequency data in terms of how our ears work.”
If you are experiencing signal degradation on your two way radio, there may be numerous causes for this. ‘Wireless Woman’ a writer with an brilliant website about two way radios, has this to say:
So there you have it.