It looks as though Google is poised to significantly expand its role in radio, as it’s hiring large numbers of radio sales people.

Other signs that it may be trying to take a bigger chunk of the $20 million industy is that Google is starting a public beta of Google Audio Ads before the end of the year. The service lets advertisers sign up online for radio ads in the same way they do to buy ads online, through AdWords.

Analysts also believe Google may be in talks already to acquire $1 billion in radio advertising inventory from Clear Channel Communications, which is rumoured to be for sale. The company controls nearly a fifth of all local radio industry revenues in the US.

Earlier this year, Google bought a service that links advertisers and radio stations through an automated system, paying $1 billion for dMarc Broadcasting. According to CEO Eric Schmidt, it’s part of a bigger plan to increase its role in radio advertising.