In its 47th year, the Philadelphia Folk Festival is trying to get younger.

That was the plan presented yesterday at the World Cafe Live, where organizers unveiled the lineup for this year's festival Aug. 14 to 17, to be held, as always, on the Old Pool Farm near Schwenksville.

Acts booked for the festival include singer-songwriter Kimya Dawson (the voice behind the Juno soundtrack); roots-rocker Steve Earle and his wife, Allison Moorer; country-rock sibling act the Felice Brothers; Philadelphia psychedelic-folk band Espers; West Chester gospel rockers Hoots & Hellmouth; and Kensington bluesman Jack Rose.

On a more familiar front, Judy Collins will headline the Saturday night show on the 90-acre site. Also on the festival bill are heritage acts such as Janis Ian, Al Stewart, Tom Paxton and Cajun dance band Beausoleil.

The folk festival is the longest continuously running U.S. festival of its kind, according to WXPN-FM DJ Gene Shay, the host and the godfather of the Philadelphia folk scene.

But in recent years, "our core audience is atrophying," Shay said yesterday, before Hoots & Hellmouth hollered and stomped, and Baird sisters Laura and Meg, of Espers, spun a web of ethereal folk in afternoon performances at the University City venue.

"We're reinventing ourselves, in a way," said Shay, 73. "People who come to the folk festival are getting to be too old to sit on a muddy hillside in the rain. We have a tradition to uphold, but it has to get younger to survive."

This year, the festival brought in Jesse Lundy and Rich Kardon of Point Entertainment, of the now-defunct Bryn Mawr coffeehouse The Point, to book the festival.

"This is not your father's Philadelphia Folk Festival, though he's definitely going to want to be there," Kardon said. And 'XPN radio personalities David Dye, Helen Leicht and Kathy O'Connell will all present acts at the fest.

'XPN general manager and frequent folk-fest camper Roger LaMay said that the radio station, whose own XPoNential Music Festival will take place July 11 to 13 in Camden's Wiggins Park, will have an unofficial but "supportive" relationship with the folk fest. "We think it's a great institution."

But it's an institution that has struggled in recent years as it has stuck with stalwart acts like Arlo Guthrie and Taj Mahal and failed to generate new generations of fans.

For its 40th anniversary year in 2002, the festival drew nearly 40,000 people over three days, said Lisa Schwartz of the Philadelphia Folksong Society, which runs it. Last year, hurt by torrential rains on Sunday, the event pulled in closer to 20,000.

"There has been some attrition of the audience," said Schwartz, who's been attending the festival for more than 30 years and whose husband proposed to her last year during Son Volt's set.

"The festival has a lot of stuff to contend with. The good news is that in Philadelphia there are an absolutely unbelievable number of cultural opportunities. But the bad news is that in Philadelphia there are an absolutely unbelievable number of cultural activities."

And the folk festival requires a commitment. "People get analysis paralysis," Schwartz said. "There are so many choices that people can't decide. We have a core constituency of people who come every year, but we need to expand that."

Contact music critic Dan DeLuca at 215-854-5628 or ddeluca@phillynews.com. Read his blog, "In the Mix," at http://go.philly.com/inthemix.