Danger on the Air (1938).

Lee J. Cobb in
Danger on the Air (1938)

An unpopular sponsor is murdered during a radio broadcast, and an engineer (Donald Woods) investigates. This comedic mystery, based on Death Catches Up with Mr. Kluck by Xantippe (aka actress, writer, and radio producer Edith Meiser), features Nan Grey, William Lundigan, and Lee J. Cobb.