Here's why Beyoncé could be heard all over S.F. Ear-splitting concert's sequel tones it down - slightly

Cynthia Faison and daughter Ashley arrived from Sacramento without tickets, so they sat outside AT&T Park, hoping they'd get in to see the show. Many S.F. residents were able to hear the concert without tickets. less Cynthia Faison and daughter Ashley arrived from Sacramento without tickets, so they sat outside AT&T Park, hoping they'd get in to see the show. Many S.F. residents were able to hear the concert without ... more Photo: Michael Short, The Chronicle Buy photo Photo: Michael Short, The Chronicle Image 1 of / 32 Caption Close Here's why Beyoncé could be heard all over S.F. 1 / 32 Back to Gallery

Unlike most concert acts at AT&T Park, Beyoncé and Jay Z kept the viewing area open in the right-field fence so fans could watch Tuesday and Wednesday's shows for free.

But their generosity didn't stop there. With booming speakers and deep, penetrating bass lines, they also broadcast to much of San Francisco, including apartments and stores miles away. Some residents were happy to listen in for free, but others had everyday concerns - like sleep.

Miranda Tsang, who lives in a Bernal Heights apartment that Google Maps says is more than 3 miles from the park, says she felt like she'd bought a ticket.

"You could hear every word," she said. "I started making a set list. I would have liked to have gone to sleep, but I had my own little personal concert in my room."

The Giants, who hosted the event, were made quickly aware there was a problem.

"There were a lot of calls that went into the city hotline," said Alfonso Felder, a senior vice president. "This was pretty significant. We heard a lot from adjacent neighborhoods south of the ballpark and on Potrero Hill."

Staci Slaughter, director of communications for the Giants, says team officials wanted to make it clear that they understood.

"We've been apologizing to the neighbors all day," she said Wednesday. "We've been doing concerts here for the last 15 years. Ninety-nine percent of the time there we don't have a problem. Last night we did. We've worked to make the proper adjustments."

The tour sponsors and the Giants worked hard all day Wednesday to lower the volume, at least in the neighborhoods, and it seems to have been an improvement.

The weather to blame

At Bloom's Saloon on 18th Street on Potrero Hill, the patrons could actually hear the announcers on the Giants game Wednesday night. That was impossible Tuesday.

"It was like the sound was coming right up through your feet," said bartender Sheila Dalton. "I had a full bar and I could still hear the music."

Derek Watry, an acoustic engineer and CEO at Wilson Ihrig & Associates in Emeryville, says the tweaks to the sound system may have improved things, but he thinks what we had Tuesday night was a classic inversion layer phenomenon. He said that because of unseasonably warm weather on a still night, the sound sailed out of the park and bounced off the inversion layer, bending back to earth. It touched down miles away in places like the Mission and Noe Valley.

"The noise goes up over people's heads and then lands somewhere else," Watry said. "Typically, a mile or two away is the sweet spot. That's a classic inversion layer."

Which sounds exactly like what happened.

Bass shook building

Austin Hoffman lives way out on Mission Street near Cesar Chavez, nearly 4 miles away, but the bass line from the concert shook his building.

"I could put my hand on the wall and feel it," he said. "I have lived here two years, and this is the first time I have ever heard anything from AT&T Park. I was wondering what it was like to actually experience the concert. It must have vibrated your entire skull."

Felder says despite the atmospheric conditions, the organizers felt some adjustments could be made to mitigate the volume.

"The weather definitely plays a factor," he said. "We had a problem one night with the Rolling Stones, and we adjusted some of the speakers for volume and direction."

But, as Watry says, it always starts with the bass.

"Low frequencies transmit better than high frequencies because they don't get absorbed by the air," he said. "More importantly, when low frequencies hit a wall they transmit through it. That's why, when your neighbor is playing his stereo too loud, you hear the bass."

And, with Beyoncé's dance beats you can expect a lot of bass. Amy Ferrara, manager of the Greek Theatre in Berkeley, says she gets complaints when acts there have a heavy bass beat.

Called an 'assault'

"If they have a whole bunch of subwoofers, sometimes our neighbors say their windows shake," she said. "They say they can feel the walls shaking. One woman compared it to an assault because it came into her home."

But for many residents that was just the start of it.

"At first I thought it was somebody in a car with the sound turned up," Hoffman said. "Then I went outside and realized that it was Beyoncé. I thought, no one in their right mind pumps Beyoncé that loud. And that's when I realized I could hear every word."

Felder thinks topography is another factor. The ballpark is on the banks of Mission Creek, which used to extend farther west.

"If you just follow the natural geography, the old Mission Creek used to travel up to the Mission," he said. "There is a corridor that the sound tends to travel up."

Loudest concert yet

Something happened. In the 15 years the park has been hosting concerts, the centerfield stage has featured everyone from Green Day to Bruce Springsteen to Paul McCartney. None of them has caused such a sensation.

And it should be said that not everyone was upset. The Twitterverse was full of comments like the one from Irvin, who said, "I can hear ... the concert from Geneva and Rolph (out by McLaren Park) and I'm not complaining."

But as his walls shook and his bedtime was postponed, Hoffman had trouble finding the silver lining.

"The worst of it," he said, "is that I'm not even a Beyoncé fan."