I sometimes watch BBC channel and see heavy debate in the British parliament. What interests me is, when one politician speaks about one policy and expresses his own view on something, some other politicians stand up and yell 'whooo.....'. Can you explain this phenomenon for me? Why do they yell? In support of the speaker or against him?
During a debate in the house of commons, the MPs shout out their support or their disagreement for a statement being made . So they shout in both cases, a "Yeahhh" for support and a sort of "No/Whoo" for their disagreement.
Of course the Tories shout their support for a statement being made by a conservative MP and the Labour MPs for a statement being made by one of their party.
Have a look at a debate between David Cameron and Gordon Brown to get a impression for people who haven't seen it.
Why they are doing this? This is what I found on www.parliament.uk
The form and style of debate in the House of Commons
The style of debate in the House has traditionally been one of cut-and-thrust; listening to other Members' speeches and intervening in them in spontaneous reaction to opponents' views.
This style of debate can make the Commons Chamber a rather noisy place with robustly expressed opinion, many interventions, expressions of approval or disapproval and, sometimes, of repartee and banter.
Ultimately it is the Chair, The Speaker of the House of Commons, who controls the House and who speaks and when. Members have the right, when speaking, to be heard without unendurable background noise (deliberate or accidental) and the Chair will call for order if it appears there is an attempt to drown out a Member or when a number of Members are leaving the Chamber, or conversing loudly.
The rules on what can be said in Parliament are old and basically boil down to members not interrupting each other, except to say "hear, hear" at the end of a sentence they agree with. So most of what you hear is MPs saying "hear, hear" to indicate agreement.
The origin of this phrase seems to be a shortening of "hear him, hear him", which in old English means "listen to him".
MPs do sometimes also boo and hiss, or laugh. Clapping is forbidden as it got out of hand in the past, and in theory MPs are supposed to listen to each other without interruption. In practice you often have to shout to be heard during a lively debate.