Web search leader Google is hiring scores of radio sales people and is spending heavily in a bid to expand its position in the $20 billion radio industry.

Google spokesman Michael Mayzel said this week that the company will begin a public test of Google Audio Ads by the end of the year. Advertisers will be able to go online and sign up for targeted radio ads using the same AdWords system they use to buy Web search ads.

Google is generally testing its ability to move into offline media, this week saying it would help customers buy advertisements in 50 U.S. newspapers.

It made a clear move into radio in January when it agreed to pay more than $1 billion, depending on performance, for dMarc Broadcasting Inc., which connects advertisers to radio stations through an automated advertising system.

It's all part of what Google Chief Executive Eric Schmidt has said is an investment in radio advertising that could grow over time to include up to 1,000 Google employees -- not just in ad sales, but also in engineering and operations.

"Google is hiring salespeople in most major markets and they're hiring sales people to sell radio. They're paying about 50 percent more than a typical radio sales person might make," said Bill Figenshu, chief operating officer of Softwave Media Exchange Inc, a unit of SWMX Inc .

Figenshu said three people he had spoken with believed Google was in talks to buy about $1 billion in radio advertising inventory from Clear Channel Communications Inc. Softwave Media Exchange sells radio ads online and competes with Google's dMarc.

Google's move into radio comes at a time when Clear Channel, the biggest radio station operator, is weighing a possible sale of the company.