Sound Systems: Electronics for Sports Facilities

Too Soft or Too Loud?

Outdoor stadiums don't have walls or a ceiling, so reverberation isn't a problem. Actually, the problem with outdoor sound is the opposite. Since there are no room boundaries to reflect the sound, the distance from the loudspeakers will directly affect the loudness level. This is why an outdoor sound system has to work harder. The level of sound at the loudspeakers must be much louder in order to overcome this loss in loudness over distance.

Figure 1

In addition, all sports events suffer from a common problem: the crowd noise is very loud. In order for the announcer to be heard, the sound system has to be louder than the crowd (See Figure 1). This is basically a problem of dynamic range. Simply, dynamic range is the spread between the softest sound that can be heard and the loudest sound possible. Here's an example. You are riding in your car listening to classical music. A quiet passage becomes difficult to hear above the road noise, so you turn up the car stereo. A few moments later, the orchestra begins to get louder. Within seconds the music is at an ear splitting level and your car stereo is crying for mercy. In this example, the dynamic range is the difference in volume between the loudest sound that the car stereo can produce with out self-destructing (or destroying your hearing) and the softest sound that can be heard above the road noise. In terms of an outdoor sound system, the announcer's voice must be turned up loud enough to be heard in a normal speaking level. However, when the an-nouncer begins to shout in excitement or to overcome a roaring crowd, the sound system level should be reduced to protect the loudspeakers from damage and the crowd from hearing loss.

Electronic devices known as compressor/limiters were made just for this purpose. This type of device reduces the extreme dynamic range of a voice or music and also limits the maximum level the sound system can produce. A compressor/ limiter can be inserted into the system so the announcer does not have to shout to be heard. It also reduces the level when the announcer does shout. If the right compressor/limiter is chosen and set up correctly, it can also provide system protection so the sound system has an overall limit of how loud it can be adjusted. This protects the system loudspeakers and electronics from damage.

Don 't Wait . . . Ask for the Equalizer!

Not only does the an-nouncer have to be heard, he must be understood. An equalizer is often useful in improving intelligibility. Equalizers adjust the tonal balance of a sound system by increasing or reducing specific frequencies of sound. A basic example of this can be found on most home hi-fi or car stereo systems. The bass and treble controls are used to adjust the balance between low and high frequencies. A 1/3 octave band equalizer does the same thing as your hi-fi bass and treble controls, only much more accurately. A 1/3 octave band equalizer can be used to compensate for the absorption of high frequency sounds in outdoor systems. They can also be used to compensate for handheld microphone applications.

When the announcer gets very close to most directional microphones, the bass (low frequency) response is boosted. This is called proximity effect. This makes the announcer's voice very boomy and indistinguishable. Using a 1/3 octave band equalizer, the low frequency response of the system can be re-duced to compensate for the bass boost. This results in better intelligibility. Finally! The participants' names can be heard above the crowd after a touchdown! The music for the dance line can be enjoyed! The group at the next pep rally can be understood!

Custom-tailored Sound for Each Event

Recently many equalizer manufacturers have introduced digital programmable equalizers that allow the user to set and program equalizer settings and store them for future use. For example, the gymnasium equalizer could have separate programs for assemblies, basketball games, dances, half-time presentations, etc. This allows any staff member the ability to choose, with a single switch, the equalizer settings for a particular event.

Summary

These different pieces of equipment can be very helpful if applied correctly. They cannot take the place of good sound system design or correctly chosen loudspeaker components. They can, however, im-prove a marginal sound system. Your existing sound system could sound better than you ever imagined. When included in a new sound system design, these electronics will help the system achieve quality sound with good protection for your new system.

by Travis Ludwig © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com

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