A-WEIGHTING: A means of adjusting frequency specific sound pressure level measurements to reflect the approximate response of the human ear. A-weighting adjustments to full octave frequency bands are: -26dB @ 63Hz, -16dB @ 125Hz, -9dB @ 250Hz, -3dB @ 500Hz, OdB @ 1kHz, + 1dB @ 4kHz and -1dB @ 8kHz. (See definitions of Sound Pressure Level; C-Weighting.)
AMBIENT SOUND: The all encompassing sound associated with a given environment at a specific time. Usually it is a composite of sounds from many sources and directions, but not including any contribution from specific noise sources under investigation.
AUTHORIZED PUBLIC EVENTS: One time, special outdoor events, conducted pursuant to and in accordance with a city issued permit or with city authorization. For the purposes of the exemption from the provisions of this chapter, all events thus authorized shall begin no earlier than seven o'clock (7:00) A.M. and terminate no later than ten o'clock (10:00) P.M. on weekdays and eleven o'clock (11:00) P.M. on weekends.
C-WEIGHTING: A means of adjusting frequency specific sound pressure level measurements. C-weighting adjustments are made to only three (3) octave bands: -1dB @ 63Hz, -1dB @ 4kHz, and -3dB @ 8kHz. The use of C-weighting produces a nearly flat (unweighted) response, and gives a more accurate indication of low frequency energy than A-weighting. (See definitions of Sound Pressure Level; A-Weighting.)
COMMERCIAL AREA: Any area zoned and/or utilized for commercial purposes.
COMMERCIAL PROPERTY: Any premises, property or facility located in a commercial area.
CONTINUOUS NOISE: A constant or continual sound, or a repetitive series of sounds, lasting more than five (5) minutes in any fifteen (15) minute period.
DAY-NIGHT AVERAGE SOUND LEVEL (DNL. L d n): The twenty four (24) hour equivalent continuous (A-weighted) sound level, in decibels, from twelve o'clock (12:00) midnight to twelve o'clock (12:00) midnight, obtained after the addition of ten (10) decibels to sound levels from twelve o'clock (12:00) midnight to seven o'clock (7:00) A.M., and from ten o'clock (10:00) P.M. to twelve o'clock (12:00) midnight.
DAYTIME: The period of day from seven o'clock (7:00) A.M. until seven o'clock (7:00) P.M.
DECIBEL (dB, dBA): A logarithmic unit of measure based on the ratio of a measured parameter to a reference unit. (See definition of Sound Pressure Level.)
ELECTRONICALLY AMPLIFIED SOUND: Any sound which has been amplified, enlarged, manipulated or produced by any electronic process or means, e.g., loudspeaker system, public address system, sound amplification equipment, or any such similar device.
EMERGENCY: Any occurrence or circumstance involving physical trauma, property damage, actual or potential loss, and/or endangerment of the public, which demands immediate attention.
EMERGENCY VEHICLE: Any police, fire or other public service vehicle or conveyance which is actively engaged in emergency work, emergency transportation, firefighting or law enforcement activities.
EMERGENCY WORK: Any activities, performed by authorized individuals or organizations, in the course of or pursuant to an emergency situation. This includes firefighting, law enforcement, infrastructure repair, delivery of essential services, and activities necessary to prevent a potential emergency from occurring.
EQUIVALENT CONTINUOUS SOUND PRESSURE LEVEL (Leq): The level, in decibels, of a steady sound which, over a stated time period and at a stated location, has the same A-weighted sound energy as a time varying sound. (See definitions of Sound Pressure; Sound Pressure Level; Maximum Sound Pressure Level.)
EVENING: The period of day from seven o'clock (7:00) P.M. until ten o'clock (10:00) P.M.
FREQUENCY (Hz): In acoustics, the number of times in one second that a sound pressure wave fluctuates about a reference point. One hertz (Hz) is equal to one cycle per second. Humans are capable of hearing sound with frequencies from approximately 20 Hz to 20,000 Hz.
HERTZ (Hz): See definition of Frequency.
INDUSTRIAL AREA: Any area zoned and/or utilized for industrial purposes.
INDUSTRIAL PROPERTY: Any premises, property, facility or equipment located in an industrial area.
INTENSE PURE TONE: Any pure tone source of thirty (30) seconds duration or longer, in which the instantaneous sound pressure level of the one-third (1/3) octave frequency band containing the tone exceeds the arithmetical average of the sound pressure levels of the two (2) contiguous one-third (1/3) octave bands (upper and lower) by eight (8) decibels or more for frequencies 500 Hz and above, and by eleven (11) decibels or more for frequencies below 500 Hz.
MAXIMUM SOUND PRESSURE LEVEL (Lmax): The highest sound pressure level observed during a measurement. On meters equipped to capture and record this parameter, it is the highest RMS sound pressure level which occurs during a measurement interval. This is not the same as "peak level". (See definitions of Sound Pressure; Sound Pressure Level; Equivalent Continuous Sound Pressure Level.)
MOTOR VEHICLE: Any nonagricultural land vehicle with mechanized (nonhuman) propulsion, including, but not limited to: automobiles; trucks, buses; recreational vehicles; motorcycles; motorized bicycles, off road vehicles; high performance, racing and/or competition vehicles; trucks and tractors modified for nonhighway use; snowmobiles.
NIGHTTIME: The period of day from ten o'clock (10:00) P.M. until seven o'clock (7:00) A.M.
NOISE/SOUND SOURCE: Any building, structure, property, equipment, vehicle, operation, process, action, person, or phenomenon which generates and/or propagates a sound or noise.
OCTAVE: The frequency interval between two (2) sounds whose frequency ratio is one-half (0.5) or two (2).
OCTAVE BAND: A standardized segment of the audio frequency spectrum, one octave wide, with a defined center frequency. Standard octave band center frequencies are 63, 125, 250, 500, 1000, 2000, 4000 and 8000 Hz.
ONE-THIRD OCTAVE BAND: Similar to octave bands, except the bandwidth is only one-third (1/3) of the full octave bandwidth. One-third (1/3) octave analysis provides a more detailed spectrum, which is necessary to identify pure tone components.
OVERALL (OR LINEAR) MEASUREMENTS: A logarithmic summation of frequency specific sound pressure level measurements (octave band or 1/3 octave band measurements). Overall measurements are single number descriptors of sound pressure level.
PERCENTAGE EXCEEDANCE SOUND LEVEL (L10, L90, Etc.): The A-weighted sound level, in decibels, equaled or exceeded by a varying sound source during the stated percentage of a measurement period. For example, L10 = 80 dBa would indicate that the A-weighted sound level exceeded eighty (80) decibels for ten percent (10%) of the measurement period.
PERSON: Any individual, group of individuals, corporation, company, association, society, firm or partnership; the state or any political subdivision, agency or instrumentality of the state. Any entity, as described in the preceding sentence, which produces or creates electronically amplified sound, which owns and/or operates any facility where electronically amplified sound is created or produced, or which is responsible for planning, promoting or scheduling any event that produces or creates electronically amplified sound.
PUBLIC PROPERTY: Any real property, or structures thereon, that is leased, owned or controlled by a public or governmental entity, or privately owned property open to the public.
PUBLIC RIGHT OF WAY: Any street, avenue, boulevard, road, alley, highway, freeway or sidewalk that is leased, owned or controlled by a public or governmental entity.
PURE TONE: A sound or noise which has distinct and identifiable tonal components and a duration of thirty (30) seconds or longer. A pure tone exists if the instantaneous sound pressure level of the one-third (1/3) octave frequency band containing the majority of the tonal energy exceeds the arithmetic average of the sound pressure levels of the two (2) contiguous one-third (1/3) octave bands (upper and lower) by five (5) decibels or more for frequencies 500 Hz and above, and by eight (8) decibels or more for frequencies below 500 Hz. (See definition of Intense Pure Tone.)
RECEIVER/RECEIVING PROPERTY: Any person who hears, or any property or location which is subject to and/or affected by a noise source.
RESIDENTIAL AREA: Any area zoned and/or utilized for residential purposes.
RESIDENTIAL PROPERTY: Any premises or property located in a residential area.
SCHOOL SPONSORED ACTIVITIES: Any outdoor activity or event which is authorized by a legitimate school or educational authority.
SOUND: A pressure fluctuation in the air that is capable of being detected by the human ear. Important characteristics of sound are the amplitude of the pressure wave (level), the frequency (pitch), and the time duration of the sound.
SOUND PRESSURE: An instantaneous increase/decrease in local atmospheric pressure produced by acoustical or sound energy, measured in pascals.
SOUND PRESSURE LEVEL (SPL, Lp): A logarithmic representation of the amplitude of a sound wave. Sound pressure level, in decibels, is equal to twenty (20) times the common logarithm of the measured sound pressure, in pascals, divided by twenty (20) micropascals. (See definitions of A-Weighting; C-Weighting; Equivalent Continuous Sound Pressure Level; Maximum Sound Pressure Level.)
SPECTRUM: The total frequency specific content of a noise source, usually described/displayed as a graph of frequency versus sound pressure level.
WEEKDAY: Any time after six o'clock (6:00) P.M. Sunday night and before six o'clock (6:00) P.M. Friday night.
WEEKEND: Any time after six o'clock (6:00) P.M. Friday night and before six o'clock (6:00) P.M. Sunday. (Ord. 278, 9-16-2002)