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!? 389.30 MINNEAPOLIS CODE Sound level: A quantity measured with a sound level meter and expressed in decibels. The weighted sound level meter and frequency weighting net- work, such as A, B, C as specified in ANSI specifications for sound level meters (ANSI S1.4- 1983, or the latest approved revision). If the frequency weighting employed is not indicated, the A-weighting is implied. Sound level meter: An instrument or combina- tion of instruments, which meets or exceeds the requirements for a type SlA of S2A sound level meter as specified in American National Stan- dards Institute specification for sound level meters S1.4-1983, or it81atest revision. It is comprised of a microphone, amplified, output meter, and fre- queney-weighting networks which is used for the measurement of noise and sound levels. Spectrum: The description of a sound wave's resolution into its components of frequency and amplitude. Steady-state sound: Sounds whose average char- acteristics remain relatively constant in time. A practical example of a steady-state sound source is an air conditioning unit. Threshold of audibility: The minimum sound pressure level at which a person can hear or detect a specified frequency of sound over a spec- ified number of trials. Threshold of pain: The minimum sound pres- sure level of a sound outside the ear that will produce a transition from discomfort to definite pain. Tone: A sound of definite pitch. A pure tone has a sinusoidal wave form which changes from dis- comfort to pain. Vibration: An oscillatory motion of solid bodies described by displacement, velocity, of accelera- tion with respect to a given reference point. Wave: A disturbance that travels through a medium by virtue of the elastic properties of that medium. Wavelength: For a periodic wave (such as sound in air), the distance between analogous points on Supp. No. 16 any two (2) successive waves. The wavelength of sound in air or in water is inversely proportional to the frequency of the sound. Weighting. Prescribed frequency filtering pro- vided in a sound level meter. Windscreen. A porous device used to cover the microphone of a sound level measurement system which is designed to minimize the effects of winds and wind gusts on the sound levels being mea- sured. Typically made of open cell polyurethane foam and spherically shaped. (Code 1960, As Amend., ~ 948.090; 82-0r-163, ~ 1,8-13-82; 86-0r- 105, ~ 1, 5-9-86; 97-0r-063, ~ 4, 7-11-97; 98-0r- 099, ~ 1, 10-2-98; 98-0r-144, ~ 1, 12-4-98) 389.40. Enforcement. The director of inspec- tions and the chief of police are authorized and directed to administer and enforce the provisions of this article. (Code 1960, As Amend., ~ 948.100; Ord. of 5-11-73, ~ 1; 97-0r-063, ~ 5, 7-11-97) 389.50. Noise prohibited. It shall be unlaw- ful to make, continue or cause to be made or continued any noise in excess of the noise levels set forth in section 389.60 unless such noise is reasonably necessary to the preservation of life, health, safety or property. (Code 1960, As Amend., ~ 948.020) 389.60. What constitutes violation. (a) Any activity, not expressly exempted by section 389.50 or this section which generates sound regardless of frequency that is more than ten (10) decibels (A scale) above the ambient noise level when mea- sured within any dwelling unit (other than the one of sound source) in a condominium, townhouse, apartment house, multi-unit dwelling, single- family dwelling, or similar dwelling between the hours of 6:00 a.m. and 10:00 p.m. All measure- ments applying to the above shall be made in- doors with the doors closed, and within the dwell- ing. (b) Any activity not expressly exempted by section 389.50 or this section which generates sound regardless of frequency that is more than five (5) decibels (A) scale above the ambient noise level when measured within any dwelling unit (other than the one of sound source) in a condo- 1654.4