15 Feb Noise: Annoyance and Zoning Regulations
Noise creates annoyance through a combination of factors, both physical and psychological. In the physical realm, we include:
- The level of the noise
- The frequency (pitch) of the sound
- The sound’s duration
- Its periodicity and predictability
- Its tonal nature, and/or impulsive nature
All of this has to be compared to the background noise at the receiver (i.e., the noise that the receiver would experience in the absence of this intruding source). It is these physical factors that can be measured.
In the psychological realm, factors which have an influence on an individual’s reaction to noise include:
- The time of day that the noise occurs (relative to the receiver’s wake/sleep cycle)
- The activities of the receiver (a receiver undertaking tasks which require concentration will be more disturbed by a given sound than one undertaking tasks that require little concentration)
- The relationship between the receiver and the noise producer (one might be significantly more tolerant to a noise if one worked for, or was good friends with the noise producer)
- A fear of the noise source (people with a fear of flying can be less tolerant to airport noise)
- A sense of inevitability to the noise (individuals will complain more vigorously about a noise source if they feel that their complaints will be effective, and less if they feel that the noise is inevitable regardless of how much they complain).
There are a wide variety of ordinances or zoning regulations for noise in effect in jurisdictions throughout the world. Many of the regulations consider the zone of the noise producer, the zone of the receiver, the nature of the noise (continuous vs. non-continuous) and the time of day that the noise occurs. The zones could be a simple as “activity” and “quiet” zones, or more complex to include categories such as “industrial”, “commercial”, “active residential” and “quiet residential”. A matrix is then established to consider the interface between these zones, i.e., an “industrial” zoned source may be allowed to produce more noise to an industrial neighbour than the same “industrial” source to a residentially zoned neighbour.
There are a number of ways to consider the continuous nature of the noise. Perhaps the most common is the use of the duration versus exceedence principle. For example, many jurisdictions consider “continuous” noise to be noise with a duration of three minutes or longer in any fifteen minute time period. Noise with a shorter duration is then considered to be “non-continuous”. Acceptable limits are then placed on the noise in this zonal matrix based on whether it is continuous or non continuous.
There are other methods, however, which some jurisdictions also use to consider the fluctuating nature of the noise and one of the more common is to consider the equivalent sound level (LEQ). This is the level of an equivalent constant sound which would have the same total energy as the time varying sound being evaluated. There are sound level meters which measure and display the equivalent sound level directly. The noise contours developed by the FAA and others for airports are examples of the equivalent energy evaluation method.
Finally, the time of day that the noise occurs is considered, with the day being broken into two or more times; often “day”, “evening”, and “night”. Obviously, greater restrictions are placed on noise generated in the evening relative to that generated in the daytime, and still lower limits are placed on noise generated at night. Some jurisdictions also place special limits on noise produced on Sundays and Holidays.
The noise measure that is almost universally used for regulating community noise is noise measured with an “A-weighted” sound level meter using a “Slow” time response. These are specific meter settings and reference should be made to the American National Standards Institute (ANSI) Standard S1.4 or IEC 61672-1 and IEC 60942.