Amex,
Unless you fly a jet with the fans at flight idle then we can hear you coming a mile off, however, fixing you in our sights is not always as easy due to being in a rate 3 turn trying to get the most out of the lift we are in.
In summer a lot of gliders will go up in the bowl of the cloud while still VMC, which is where 7 out of the 11 contacts will be which is why normally you will only see 2 or 3.