http://www.musicradiocreative.com/radio-imaging/radio-sweepers
A radio sweeper is not the person who knocks about the radio station corridors cleaning up after hours. It's a tool you can use to transition between songs hence the word 'sweeper'. You literally use it to 'sweep' or segue between two songs in any music playlist. Radio sweeper effects can be whooshes, bangs or crashes mixed with voice over and no longer than 20 seconds in duration.

You can use it to identify the radio station and the radio station tag line too. Radio sweepers are great for transitioning from fast music to slow music or vice versa. You can also play them over the intros of songs too.

Find radio imaging FX at AudioJungle. I made a video to show you how to do it: http://youtu.be/Ntba03kGWTk