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Drive Thru

Almost exactly 25 years ago, in June of 1982, I had the opportunity to help design and set up a portable sound system for the first ever Detroit Grand Prix, a Formula 1 event that took place on city streets near the Renaissance Center in Detroit, MI. I was working with Community Loudspeakers at the time, and our products had been chosen to provide sound for the event. It was a pretty exciting time at Community. The M4 Midrange Driver was new and the Detroit Grand Prix was a great opportunity to demonstrate its high-power, outdoor voice reinforcement capabilities. But we gained far more than product exposure at the Detroit Grand Prix. In particular, I learned several important lessons about racetrack sound.

1. You Need Good Partners
Our dealer, Arnold Williams Music, worked with Destiny Sound and the local phone company to set up the systems and provide cabling over the 2.5-mile course. They did a great job.

2. Formula 1 Racing Is Loud
I probably don't have to tell you this, but motor racing is very loud. We measured A-scale sound levels exceeding 140 dB at the street level when the cars went past. Bring your earplugs!

3. Don't Put The Announcer's Booth At The Track Level
The city had a temporary announcer's booth at the finish line. It had absolutely no sound isolation-not even a window. When the cars roared past, the motor noise at the microphone was so loud that we amplified the car noise more than the announcer.

To help solve this, I put together a makeshift differential mic from a pair of small diameter omnis we found somewhere. This is an old-timer's trick. You tape the two mics together with the second mic about a half-inch behind the first. Reverse the polarity on the second mic and teach the announcer to close-talk the first mic as close as he or she can get. At the Detroit event, this cut the motor noise problem substantially.

4. Don't Try To Out-Shout The Cars
All of the seating was within a few yards of the track, so the motor noise was very high for the audience. The Community M4 drivers and their horns were fully capable of providing announce levels above the motor noise. However, this would have produced uncomfortably high announce levels. As a partial solution, we asked the announcer to speak only after the cars had gone past and to repeat his announcements so that everyone would have a chance to hear.

5. Distributed Loudspeaker Layout Is Best
The Detroit Grand Prix had distributed seating areas, so we had no choice but to provide a distributed loudspeaker layout. However, the benefits of distributed loudspeaker systems are so great that most larger sports facilities use them today. One of those benefits is the ability to keep more of the sound inside the facility. This way, the neighbors may complain about the motor noise, but they are less likely to complain about the sound system.

6. What I've Learned Since
Okay, I've learned a few things since 1982. I now believe that, under controlled conditions, it is possible to achieve intelligible voice paging even if the paging level is several dB below the track noise. To achieve this, start with a well designed, distributed loudspeaker system using high-quality, high-output loudspeakers and high-power amplifiers. You also need a trained announcer using a good noise-canceling microphone in a sound-isolated booth. Use a broadcast-style compressor (not just a limiter) and add a few dB of extra boost from 2 to 6 kHz. Then, suggest that the announcer repeat messages. Most professional sports announcers do this anyway.