Environmental NoiseOctober 8, 2019
Loudest Recorded Sounds on the PlanetDecember 16, 2019
Nuisance Factors and Noise Ordinances
In this, the second of our ongoing series intended to help our readers better understand what is involved in the study of environmental noise, we address nuisance factors and different types of noise ordinances created to limit the transfer of noise from one property to the next.
What factors make a sound a nuisance?
Is it wanted? Since "Noise" is defined as "unwanted sound", this is the critical factor. A "sound" is what we make. A "noise" is what someone else makes. Noise is the sound of a party to which we weren't invited! Similarly, noise from industrial or commercial centers is better tolerated in a community where the residents' livelihood and/or the local economy is dependent upon the work carried out there.
The noise level. Some noise levels are too loud and annoying no matter when, or for how short a duration, they occur. Each community sets its own standards as to how much is too much.
The time of day. The noise level in our environment can be more or less annoying depending on the time of day. While we are active in our community during business hours, often we don't notice the noise level. But in the evening, nighttime, and early morning, the same noise level can be highly intrusive and irritating.
The character of the noise. A simple tone or "hum" created by rotating machinery (e.g. an air conditioner), impulsive sounds (sudden repeated or irregular noises like hammering), or sounds composed of speech and/or music can be very disturbing. Most jurisdictions penalize these types of sound with a +5 dB correction.
What is a noise ordinance?
A noise ordinance is a set of rules to establish the permissible level of noise that can propagate from one property to another, and is an integral part of municipal code. The provisions attempt to take into consideration the nuisance factors described above. The noise levels promulgated by the ordinance can be absolute, tiered or relative.
How do noise ordinances differ?
Many noise ordinances quote an absolute level that may not exceed when measured at a source property line or on the receptor property at certain times of day or night. Absolute levels are easy to assess and to apply. Tiered levels can be difficult to apply. They are stated, for example, as: "Noise level that cannot be exceeded for a cumulative period of more than 30 minutes in any hour - 60 dB(A) daytime, 55 dB(A) nighttime; 15 minutes in any hour - 65 dB(A) daytime, 60 dB(A) nighttime; 5 minutes in any hour - 70 dB(A) daytime, 65 dB(A) nighttime" etc. The difficulty arises in the interpretation of the noise level once it has been measured and any penalty for the character of the noise has been added to the measured level.
Relative levels with respect to the local ambient noise, state that a noise source may not exceed the ambient plus x dB. If no ambient level is quoted, such ratings invite argument. What exactly does ambient include? To further muddy the waters, some ordinances define the presumed ambient plus x dB as the to-not-exceed standard, which can lead to inequitable results. An actual "live" ambient measurement at the specific location in question will always give a more accurate level.
In our next article we will look at noise measurement equipment and how to accurately take noise measurements to verify compliance with standards.