SIOUX FALLS, S.D. (KELO.com) -- The City of Sioux Falls Health Department issued the following Frequently Asked Questions today regarding noise and noise ordinances in the city.
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This document answers some frequently asked questions regarding environmental noise regulation as it pertains to Chapter 93 of Sioux Falls City Ordinance.
Q: How does Chapter 93 regulate noise from an address?
A: Noise is defined as unwanted sound. Chapter 93 identifies sound levels in decibels for various land uses. These decibel limits are measured by the use of the L90 over the span of 10 minutes.
Q: Why is land use used as an identifier rather than zoning districts?
A:While it has been previously discussed to change the limits to zoning districts rather than land use, it was determined that land use is the most equitable distinction, as it represents individual citizens and businesses more fairly by giving both equal value for their given use.
Q: What is the L90?
A:The L90 reading is an average of the sound produced 90% of the sample time, in this case 10 minutes. This is measured by the sound meter recording the peaks and valleys of sound produced, then eliminating the bottom 10% and averaging the remaining 90%.
Q: Why use L90?
A:By discarding the bottom 10% of readings (people don’t complain about it being too quiet) it removes the quietest readings and leaves the sample with a representation of the loudest portion of the sample. Because noise is generally a series of sound and silence, the L90 will be lower than any given peak in the sample.
Q: Is a phone app an effective method of measuring L90?
A:No. A phone app will register peaks in real time but does not contain the appropriate software to calculate an L90.
Q: Does the location of the reading make a difference?
A:Yes. Ordinance requires sound readings to be taken at the property line of the most restrictive land use. The ordinance is written to be representative of sound as it is perceived by the human ear.
Q: Do sound waves move like water waves?
A:Sound waves have peaks and valleys similar to waves in water, but sound does not travel like water looking for a way out. Sound travels in a straight line until it hits a barrier, getting less and less intense as it moves away from the source. This means that sound absorption material or barriers placed between the source and the receiving land will lessen the impact of the sound. Sound also bends and reflects back from solid objects such as brick and concrete. For this reason, sound absorption material must be properly designed.
Q: Is there an annoyance factor that comes in to play?
A:While the ordinance does not address the annoyance factor of noise, it does play a role in complaint resolution. The ordinance addresses the loudness (decibels) of the sound, but people can be affected differently by various aspects of sound. For example: how clearly the sound can be heard, the frequency of the sound (high, moderate or low pitches), the nature of the sound (pleasing, such as running water or not pleasing, such as spoken profanity). These things are not regulated by Chapter 93.
Q: Why regulate environmental sound?
A: It has been shown that exposure to excessive environmental sound can adversely affect the health of a community over time. This can lead to symptoms of anxiety, high blood pressure and has shown to be a factor in anger management and domestic violence.
Q: Is a sound permit an option offered by Chapter 93?
A: A sound permit is generally for outdoor events and issued on a case by case basis taking in to account things such as stage placement, speaker placement, previous complaints and potentially a sound check. Permits are issued to allow for an excess of sound beyond the stated ordinance limits and are intended for events and special uses. Chapter 93.007 allows for an L90 of 70 dbA in the Sioux Falls Business Improvement District for the purpose of music or entertainment between the hours of 6AM and 10:30PM, except Friday and Saturday nights when they can be granted between the hours of 6AM and 11:30PM.
Q: Does the City Health Department regulate sound inside a building?
A: City ordinance 93.002(6) states:
(6) Enclosed places of public entertainment. Operating or permitting to be operated in any place of public entertainment any loudspeaker or other source of sound which produces, at a point that is normally occupied by a customer, maximum sound pressure levels of 100 dB(A) as read with the slow response on a sound level meter, unless a conspicuous and legible sign at least 225 square inches in area is posted near each public entrance stating: “WARNING: SOUND LEVELS MAY CAUSE HEARING IMPAIRMENT.” This division (b)(6) shall not be construed to allow the operation of any loudspeaker or other source of sound in a manner as to violate § 93.003;