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Biamp Systems' AudiaFLEX and Sona

When the NCAA decided to move the Final Four portion of its national collegiate basketball championship to Ford Field in Detroit three years ago, the world watched as basketball was elevated to an even bigger stage. Yet while the change offered more people the chance to see the games live, it presented some unforeseen challenges in trying to preserve the feel and spirit of the games that fans nationwide had come to enjoy in arenas half the size of Ford Field.

So the NCAA enlisted the help of Coffeen Fricke & Associates to develop a system to meet the different acoustic challenges that the larger football stadiums presented, specifically acoustic intimacy.

In a basketball arena, fans typically sit on the floor, at the same level as the game. A football stadium the size of Reliant Stadium in Houston — with a capacity of more than 77,000 — doesn't have the same audio coverage because fans are sitting below the floor and further back, much more spread out. So those who attended the initial games in these larger venues commented that the games lacked the same feeling as a typical basketball arena.

The plan devised by Coffeen Fricke called for a single Biamp Systems AudiaFLEX with a SONA acoustic echo cancellation (AEC) card. (See Figure 1.) The fix combined taking live feeds from the CBS live broadcast — the one that picks up the live court sounds such as shoe squeaks, hoop swishes and rim rattles — and mixing those inputs with microphones that sit on the court. These “sound effects” were then mixed back in to the house sound, so that audience members sitting in the farthest seats would still get an experience that sounded as though they were sitting courtside.

Stephen Solberg, a senior associate with Coffeen Fricke, said the firm had used AudiaFLEX previously, but this setup was different. The distance between microphones and speakers was approximately 35ft, rather than 8ft-10ft as found in a boardroom setting. They also had to compensate for much more powerful speakers, Electro-Voice line arrays in this case. In the end, the system worked wonderfully.

The concept had been tested and applied in tournament finals games the last two years. However, in each instance, the remixed sound was causing echoes in the CBS broadcast mix. This was due to the announcer's voice being picked up a second time, creating a distracting echo in the CBS feed that prompted CBS producers to ask that the Coffeen Fricke microphones be switched off to eliminate the echo. This year, with Biamp SONA applied, the team was able to eliminate any echo and still provide the sounds of the game to the live crowd.

To solve the echo problem, a single AudiaFLEX was programmed with SONA acoustic echo cancellation to remove the announcer's voice from the feed back to the arena. The system received 10 mic feeds on the court, six from CBS and four of its own, and two additional inputs from the house feed to serve as reference points for what SONA should subtract from the court mics. It handled echo cancellation only and then sent all signals straight out to a Mackie console for a full mix. AudiaFLEX processing also performed some band limiting to isolate the desired effects from other things happening in the arena. The tuning of the arena was done on the actual arena house system.

The bandwidth of the SONA handled the acoustic demands of the stadium and its speakers. The AEC was run all the way out to 20kHz, and it handled the extremes well.

The raw feed that was being sent back to the house, with the long reverb time and the long distance between the mics and speakers, sounded strange acoustically. The direct announcer's voice that was being fed in to the PA was missing completely, but all of the reverberant tail in the room — approximately 7 seconds worth — was still there, because it was never there in the reference. When the team fed it back in to the arena, it actually sounded good.

Bob Ledo is senior vice president of Coffeen Fricke & Associates.