There's an article about It's a Mad, Mad, Mad, Mad World here and another one over here. The first of these pieces notes…
Karen Sharpe Kramer said her husband also broke cinematic ground with the project, presenting it in the then-new process of Cinerama, and keeping the show going during the intermission with an interactive feature — the playing of scripted police radio transmissions over speakers located throughout the theater.
The male voice on many of those faux police calls was that of the aforementioned Lennie Weinrib, who is also heard in many places during the film. He's most identifiable as the voice on the police radio that announces that the cabs are chasing Captain Culpeper, and dubbing for the stuntmen at the end who play fire fighters.
Lennie may be better known to you from his many on-camera appearances which ranged from Magic Mongo to The Dick Van Dyke Show. On the latter, he was the guy who phoned Rob, got him to dismantle his phone and told him to "Scream like a chicken!" He was in two other episodes of that, as well, and just about every sitcom of the sixties and seventies. His voice appeared on hundreds of cartoon shows, and many a Krofft production. He was the voice of H.R. Pufnstuf, for example. A talented, funny man…and a regular reader of this website, I'm happy to say.