By Dan Daley
SVG Audio Editor

Last year during a crucial MLB game at Yankee Stadium last year, play was halted so the umpires could discuss whether a fly ball down the line had hit the foul pole or whether a fan interfered. The umpires made their call based on their visual from the field. But Fox Sports Senior Audio Mixer Joe Carpenter, just like a crime scene expert, has access to a set of audio tools that let him discover the truth. Welcome to CSI: Yankee Stadium and the world of audio forensics.

Carpenter routinely places crowd microphones on foul poles and, during the years, has learned what it sounds like when a ball hits a foul pole. The next day, he went to scene of the foul and tapped the pole, with a colleague monitoring the channel in the audio truck. “We didn’t hit it as hard as it would have been if it was a baseball slamming into it,” he says. “But when we checked the recordings of the previous night’s game, we determined that the ball definitely did not hit the foul pole.”

Carpenter says some stadiums have a yellow line that runs along an outfield wall that’s used to call a home run if [the ball] goes above it. "Usually, there's signage above that line," he says. "When it's a close call, we can check the recording to see if we hear the signs being hit. Then we know it was a home run."

MLB will be in its third season in 5.1 Surround Sound this year, and the prolificacy of microphones around the field would delight any forensics specialist. "There's very little you can't hear from the field," says Carpenter. League rules forbid "snooping"microphones that can pick up strategic chatter (or the occasional FCC-alerting f-bomb) from dugouts. But for the World Series last year, the audio crew managed to get plenty of sound from the covered bullpen at Fenway Park. Pitchers, catchers and coaches will often use plastic bottles and other paraphernalia to bang on the roof during rallies. "We made sure to position our crowd microphones to be able to pick that up," says Carpenter.

Unfortunately, time constraints during regular season games compel the audio crew to mix in stereo. That feed gets upmixed in Hollywood and is used for the HD broadcast. But full 5.1 Surround Sound miking is used for the All-Star and post-season play.

The central weapon in the microphone closet for Carpenter this season is the Sennheiser 8000 short shotgun microphone, which he began working with in prototype form during post-season play last year. Working with both the cardioid and hypercardioid versions, Carpenter used them to create the surround sound array of the ball field, with 8000s in centerfield aimed straight at the plate and others positioned down the base lines. Three microphones in parabolic capsules, sometimes the 8000, sometimes a Sennheiser MKE2 lavalier, cover the plate itself two along the base lines and one directly behind the umpire. "That's the one that gets the calls," he explains.

The other two dishes will start the audio pursuit of the ball after a hit, with the crowd noise along the trajectory boosted as it sails past, and into the surround channels created by a pair of microphones in the centerfield position. "In most situations, you're watching every pitch from behind the pitcher," he says. "So the rear channel is set up that way, too."

But the real challenge for MLB audio is that, unlike other sports that have clearly defined playing field, every baseball stadium is different. "As soon as the ball is hit, camera 2 is the first cut," he says. "You want your microphones placed where the ball tend to go, and that's different for every field. At Fenway, for example, the Green Monster is a magnet, so you want to have crowd mics up there. It's just like forensics: you just follow the trail."

Could audio forensics one day be part of an instant replay system in MLB? For now any sort of instant replay in MLB is a dream. But a few more miscalls during a crucial game and it might be time to revisit the status quo.