New York ? “Bright. Crisp. Clean. Pure,” says the silky smooth, perfectly masculine voice on the beer commercial. “This is Budweiser. THIS is beer.”

Quick, who is that? Hint: It’s a big movie star. Though his name’s never mentioned, the makers of Budweiser are banking on the fact that you’ll get it eventually – and that you’ll say “Wow!” when you do.

Twenty years ago, voiceovers were the domain of the baritone radio announcer or the character actor. No longer. These days, more A-list stars than you might imagine are cashing in.

Kevin Spacey’s pitching Honda. Kelsey Grammer does Disney. Kiefer Sutherland voices Apple commercials, and his dad, Donald, did Volvo. There’s Queen Latifah (Pizza Hut), Sean Connery (Level 3 Communications), Christian Slater (Panasonic), Gene Hackman (Oppenheimer Funds) – oh, and then there’s Julia Roberts.

That’s right, Julia Roberts, in a recent campaign for America Online.

It seems no one’s too rich or famous to do a voiceover. It’s not too hard to see why the celebs like it: It’s an easy, lucrative form of work – a few recording sessions where you can show up with messy hair and no makeup. The more difficult question is why advertisers are willing to spend a huge chunk of their budget on a star whose voice, however distinctive, likely won’t be recognized by many.

“Honestly, sometimes I’m mystified,” says Maureen Kelly, a casting director who’s worked in the voiceover field for two decades. “I guarantee you most people couldn’t tell the AOL voice was Julia Roberts. I’m just not sure why advertisers spend this astronomical amount of money when the voice isn’t even identifiable.”

By astronomical, we’re talking seven figures, easy. Although companies won’t say how much they pay, industry experts say a megastar like Roberts would have to make well into that range.

Or George Clooney, that mysterious Budweiser voice. When Anheuser-Busch was searching for “a classic voice” last year, the company hit on Clooney as the perfect embodiment of its product. “George Clooney – it’s almost a brand in itself,” says Dan McHugh, vice president for trademark brands. “It just made a lot of sense for us.”

The idea, says McHugh, is that the consumer will “sort of know the voice. They may not necessarily place it right away, but when they do, they say, ‘Wow!'” It’s that whole intrigue of discovery.” In other words, the “cool” factor is higher because there’s mystery involved.

Advertisers didn’t always have such an array of choices. Twenty years ago, says Linda Weaver, of the Access Talent agency, jobs went to announcers from the radio world, with the so-called “Voice of God.” Martin Sheen was one of the first actors to make the plunge, voicing ads for Pepsi and Maxwell House in the 1980s.

In recent years, many rank-and-file actors have turned to voiceovers for a steady stream of income. The best of them have an impressive repertoire: they can do sexy, perky, the harried mom or the guy who drives fast cars. One good national commercial can bring in $15,000 to $20,000. A successful voiceover career can yield a comfortable six-figure income.

American stars still often head overseas for commercials that won’t be seen at home, but lately, doing it at home seems OK too. Catherine Zeta-Jones appears on camera for T-Mobile. Ellen DeGeneres does American Express. The most well-respected actresses become the “faces” of fashion and beauty houses – Nicole Kidman (Chanel), Gwyneth Paltrow (Estee Lauder), Hilary Swank (Guerlain), Charlize Theron (Dior). Brad Pitt even did a Heineken ad last year.