Stopping Disco Noise Cold

Richard J. Peppin - peppinR@Scantekinc.com
Scantek Inc., Columbia, MD USA
Joan Casamajó
DICESVA, Barcelona, Spain

Popular version of paper 3aNSb5
Presented Wednesday morning, April 7, 2003
145th ASA Meeting, Nashville, TN

Community noise is one of the prices we pay for a society that uses more and more energy as part of its living conditions. As we use more power, one of the side effects is increased noise. Nowhere is this more evident than the pervasive nature of roadway and aircraft noise. Next might be noise from air-conditioning systems and other mechanical equipment.

But some noise we make intentionally and it seems the noise from nightclubs, discos, exercise studios, theme parks, fairgrounds, and automobile dealership loudspeakers is one of the most widespread causes of citizens' complaints.

Noise that is expected, like air conditioner noise, can often be controlled simply. Barriers, maintenance, judicious site location, and noise abatement measures are some techniques manufacturers and acoustical engineers use to keep the equipment within acceptable levels. But entertainment noise, and other similarly generated noises, is unique. Mostly, the producer of the noise, such as a DJ, for example, has complete control of the volume and can often cater the volume to the preferences of him/herself or the audience. As a result the noise perceived by the community may or may not exceed local noise limits, depending on the whim of the operator. In addition the sound frequency spectrum changes almost instantaneously because of the nature of the music, so the A-weighted noise level at the property line, a very common descriptor of community noise, can vary because of changes in level or changes in spectrum.

DICESVA, an acoustical instrument company from Spain, developed a very capable device to handle this problem. It is simple to use too and, even better, indicates when and if, it was tampered with to assure compliance. Here's how it works:

1. Suppose a community near a disco (which sometimes leaves its doors open) has a noise ordinance of 55 dBA at night at the property line.
2. Suppose the disco produces noise inside that varies from 95 dBA to 110 dBA (yes, that is very loud!).
3. First an acoustical consultant produces a loud pink noise in the disco, through the sound system.
4. She leaves the doors open and measures the attenuation in the sound as it travels from the source and as it hits any barriers between the disco doors and the property line.
5. That data is input to a CESVA "Amplified Noise Limiter LRF-04" which is placed between the mixing console and the speaker amplifiers in the disco.
6. Now a tamperproof microphone is placed in the ceiling in the middle of the dance floor and connected to the LRF-04.
7. The unit is programmed to allow only 55 dBA at the property line, is scheduled for planned sessions (so that people don't play at the wrong times) and is turned on.
8. The unit controls the outgoing music so that it does not exceed the 55 dBA limit. If it looks like it is going to be exceeded it can be quickly controlled to keep it low (but the audience notices the abrupt changes) or controlled slowly to keep it low (where the 55 dBA may be exceeded but the audience will not notice much change in the volume.).
9. The data records all exceedances, all times when additional, non-controlled equipment is added, if/when someone tampers with the microphone, if the power is turned off, etc. If somehow the unit cannot possibly reduce the noise to meet the property line limits, it attenuates the sound so it is effectively silent. In addition, the LRF-04 also keeps in memory the time history of acoustical parameters measured.

Now this control system does not depend on the skill of a DJ, the level of amplifiers, or the need for a community noise inspector to be at the site to record the violations. Thiscost-effective solution is used in hundreds of discos in Europe. Its potential for noise control in the USA is great.