Following the opening of Sonoma State University's Weill Hall this fall, the $125-million concert venue has been under intense scrutiny as patrons, musicians and staff proceed through the process of evaluation and fine-tuning.

"It's been a trial period for us and our patrons, and we've taken in a lot of feedback," said Jessica Anderson, marketing manager of the Green Music Center, which oversees the hall. "The first year is about testing the waters and seeing what works and what doesn't."

During the last two concerts of the MasterCard Performance Series, the university started sending out online surveys to ticket-holders to gather even more input.

"So far, we're getting really valuable feedback," Anderson said. "And we're scoring high on overall satisfaction."

Among the MasterCard series shows, the Jazz & World Music Series has attracted the most audience members, followed closely by orchestral offerings, Anderson said.

"The vocal concerts have not sold as well as our other performances," she added. "We're working closely with the artistic administration to provide analytics on what the audience is really supporting."

Regional data collected on ticket sales reveal that the hall has primarily lured in local music lovers. Among single-concert purchases by households, 83 percent of the sales were in Sonoma County, 5.6 percent in Marin, 3.8 in the greater Bay Area, 1.9 percent in San Francisco and 1.3 percent in Napa.

One of the first things the university plans to address this year is improved signage across the campus and parking lot to help with traffic flow.

"As people are coming in, especially from the main entrance, we want to help move people to the back corner of the campus," Anderson said.

They also hope to improve the sound of amplified concerts.

"When Chucho Valdes is on tour, he has a sound team, so they do their normal set-up and work closely with us," Anderson said. "But the end result is that things are drowned out or muddled."

The hall's acoustician, Larry Kirkegaard of Kirkegaard Associates in Chicago, has been working closely with the university on fine-tuning the hall for acoustic as well as for amplified music.

Kirkegaard started the process in May 2010, when the San Francisco Symphony first took the hall for a test drive.

"Tuning began with that concert and understanding the creature we had to work with," he said of the hall. "Mostly what we do is listen. We listen to music, we listen to musicians and the conductors and what it's like for them."

The experienced acoustician already knew that the shoebox-shaped hall was superior to a fan-shaped hall. Its narrow, parallel side walls ensure clarity, since sound traveling back and forth between them reflects quickly to the listener.

"Somewhere around 60 and 75 feet of width is where the sound blends and becomes a full, rich, chewy sound," he said.

Also, the hall's walls are 16 inches thick, so that when the sound hits the walls, it doesn't create vibration or movement and lose energy.

"You want it to turn around with full energy, like a great swimmer," he said.

Height is also important to a concert hall, but that can vary according to the repertoire being performed and how much reverberation it requires.

That's where most of the customized tuning takes place at Weill Hall, which boasts adjustable fabric banners along the windows and walls at all three levels.

"What really is tuneable is the fabric that we can bring out as banners," he said. "They lower from the ceiling and unfurl."

While testing the hall with a pianist, Kirkegaard noticed that the bass, played by the left hand, was not as deep and resonant as one would expect.

"We extended the banners by 5 or 6 feet," he said. "It cleared up the bass. ... I think it took away a low-frequency reflection that was interfering with the sound."

Sound reflection off the onstage risers has also led the Santa Rosa Symphony to experiment with different riser configurations. The risers tend to reflect the sound that reaches them back to the violinists, Kirkegaard said, like a wave hitting a pier, then sending wavelets back.

While the symphony is still working on a riser compromise, Kirkegaard believes the strings will ultimately settle on playing from the flat floor.

"When you put the orchestra on the flat floor, there's a more homogeneous sound and a warmer sound," he said. "I learned this from (conductor) Marin Alsop."

Meanwhile, patrons are also experimenting with seating, moving around in the hall to try out different sightlines and acoustic preferences.

Like the musicians, they are learning to adapt, finding their favorite spots on the orchestra floor, in the back balcony, or even behind the stage.

"The delight is that you can't make it all the same," Kirkegaard said. "You want them all to be valid and unique in their own right."

You can reach Staff Writer Diane Peterson at 521-5287 or diane.peterson@pressdemocrat.com.