Hawthorne Municipal Code Art. 1 General Provisions

This objective portion of the city's noise standard restricts noise from machines, animals, or devices (or any combination thereof) from producing noise that exceeds the specified, measurable noise limits (as summarized in Tables N-1 and N-2 below). In general, this type of regulation is aimed at controlling stationary or on-going noise sources that are more established (in both location and periodicity) than the subjective-related occurrences (of Chapter 9.33). Such sources might include, for example, noisy HVAC or pool equipment, on-going loud music (over repeated instances), excessively and frequently barking dogs, or home/landscaping activities that are too early or too late in the day (see also Section 9.34.060). Such objective criteria give the city's enforcement officers the capability of demonstrating a measurable violation while using the defined enforcement procedures to document potential violations and to implement penalties (see also Sections 9.34.050 and 9.34.100).

(Ord. 2169 § 3, 2019)

Note: As a supplement to Section 17.04.010, dealing with general code definitions, the following noise- and vibration-specific definitions apply throughout.

Ambient sound level.

The sound level of the all-encompassing sound associated with a given environment, being usually a composite of sound from many sources and excluding the specific sound under investigation. For measurement purposes, the ambient sound level is equal to the A-weighted sound pressure level exceeded ninety percent of the time for sixty minutes (L90).

A-weighted sound level.

An overall frequency-weighted sound level, expressed in decibels, that approximates the frequency response of the human ear. The sound pressure level in decibels as measured on a sound level meter using the A-weighting network as specified in American National Standards Institute documents for sound level meters. The level so read is denoted as "dB(A)" or "dBA."

Code enforcement officer.

The person who is designated as a code enforcement officer under the Hawthorne Municipal Employees Association MOU or the person designated by the city manager to administer the provisions of this chapter.

Community noise equivalent level (CNEL).

The energy-average of the A-weighted sound levels occurring during a twenty-four-hour period, with five dB added to the levels occurring during the period from 7:00 p.m. to 10:00 p.m. and ten dB added to the sound levels occurring during the period from 10:00 p.m. to 7:00 a.m. See also Day-Night Sound Level.

Community noise officer.

The person, police officer or code enforcement officer designated by the city manager to administer the provisions of this chapter.

Construction.

Any site preparation, demolition (of existing facilities or structures), assembly, erection, substantial repair, alteration, or similar action, for or within private rights-of-way, structures, utilities, or similar property.

Cumulative period.

An additive period of time composed of individual time segments which are either continuous or interrupted.

Day-night sound level (Ldn or DNL).

The energy-average of the A-weighted sound levels occurring during a twenty-four-hour period, with ten dB added to the sound levels occurring during the period from 10:00 p.m. to 7:00 a.m.

Decibel.

A unit measure of sound (noise) level used to express the relative intensity of sounds on a logarithmic scale and with respect to a defined reference sound pressure. The standard reference pressure is twenty microPascals. The resulting logarithmic scale nominally ranges between zero dB (representing the least perceptible sound) to approximately one hundred thirty (representing the threshold for pain). For "A-weighted decibel," see A-weighted sound level.

Domestic animals.

Includes dogs, cats, birds (but excepting fowl), and other animals kept primarily for the purpose of personal enjoyment.

Equivalent continuous noise level (Leq); also called the energy-equivalent noise level.

The value of an equivalent, steady sound level which, in a stated time period (often over an hour) and at a stated location, has the same A-weighted sound energy as the time-varying sound. Thus, the Leq metric is a single numerical value that represents the equivalent amount of variable sound energy received by a receptor over the specified duration.

Fowl.

Domestic poultry and game birds kept chiefly for their eggs and/or flesh; e.g., a domestic cock or hen, turkey, duck, goose, and guinea fowl.

Frequency.

The number of times that the quantity repeats itself in one second (i.e., the number of cycles per second). The standard unit is hertz, denoted as "Hz" (previously, cycles-per-second). Frequency is the reciprocal of the signal's period. See also Hearing Acuity.

Hearing acuity.

Individuals differ greatly in their hearing acuity. Reasons for the differences are many, and include age, long-term exposure to high-level noise, and ear disease. 'Normal hearing' is the median hearing level of a large group of young adults of ages between eighteen and twenty-five having no know history or ear disease and no appreciable exposure to high-level noise. Hearing acuity varies by frequency content of a given sound, but the nominal frequency range of hearing is taken to be from twenty Hz to twenty thousand Hz (for the set of young adults). Presbycusis is the loss of hearing that takes place with increasing age. Such a loss occurs even for persons who are otologically normal and have not been exposed to high occupational noise levels. For an average person, presbycusis may begin to appear as early as the twenties, occurring mainly at high frequencies. Thus, older people tend to hear less high-frequency tonal content then younger people. Also, the loss is generally greater for men than women at any given sampling age.

Impact insulation class (IIC).

A single number rating used to compare the effectiveness of floor-ceiling assemblies in providing reduction of impact-generated sounds such as foot-falls or foot-steps. This rating is derived from values of normalized impact sound pressure levels in accordance with ASTM Standard E462. The impact insulation class values that are measured in the field (in-situ) are abbreviated as FIIC.

Intrusive noise.

A sound which has a variance in character such as audibility, dissonance, duration, loudness, tonality, pitch, and/or timbre and is perceived adversely compared to the character of the environment in the absence of that sound.

Noise.

Sound that is loud, unpleasant, unexpected, or otherwise undesirable.

Noise control officer.

The person, code enforcement officer or police officer, designated by the city manager or police chief to administer the provisions of this chapter or designee.

Noise-sensitive receptor (or noise-sensitive land uses).

Noise-sensitive receptors include land uses where quiet environments are necessary for enjoyment and public health and safety. Residences, schools, motels and hotels, libraries, religious institutions, hospitals, nursing homes, and community care facilities are examples. This generally also applies to vibration-sensitive receptors.

Off-road vehicle.

Any motorized track or wheeled vehicle such as, but not limited to, racing motorcycles, trail bikes, minibikes, dune buggies, or all-terrain vehicles, designed or used for ground travel over private or public natural terrain.

Sound-amplifying equipment.

Any machine or device used for the amplification of the human voice, music, or any other sound. "Sound amplifying equipment" shall not be construed as including standard automobile radios when used and heard only by the occupants of the vehicle in which the automobile radio is installed. Sound-amplifying equipment, as used in this code, shall also not include warning devices on authorized emergency vehicles or horns or other warning devices on any vehicle used only for traffic safety purposes.

Sound transmission class (STC).

A single number rating used to compare the sound insulation properties of walls, ceilings, windows, or doors. The sound transmission class is derived from measurements in sixteen test bands (of frequency). The sound transmission loss values that are measured in the field (in-situ) are abbreviated as FSTC.

Supplementary definitions of technical terms.

Definitions of technical terms not defined herein shall be obtained from the American National Standards Institute's (ANSI) Acoustical Terminology S1.1-2013, or the latest revision thereof.

Vibration decibel (VdB).

A unitless measure of vibration, expressed on a logarithmic scale and with respect to a defined reference vibration velocity. In the U.S., the standard reference velocity is one micro-inch per second (1x10-6 in/sec).

Vibration-sensitive receptor (or vibration-sensitive land uses).

As with noise-sensitive receptors (above), vibration-sensitive receptors include land uses where quiet and vibration-free environments are necessary for enjoyment and public health and safety. Residences, schools, motels and hotels, libraries, religious institutions, hospitals, nursing homes, and community care facilities are examples. Additionally, vibration-sensitive uses can extend to specialized manufacturing, research, or production facilities that require additional vibration-related precautions that are more restrictive than those associated with human annoyance. Examples of specialized uses would include most audio/video recording studios, computer chip manufacturers, and entities utilizing optical microscopes, electron microscopes, and/or micro-lithography etching/printing/inspecting equipment.

Zoning district or areas.

As defined in Title 17.

(Ord. 2169 § 3, 2019)