For the purpose of this Chapter, whenever any of the following words, terms or definitions are used herein, they shall have the meaning ascribed to them in this Section:
Acoustical Terminology, Definitions of:
All acoustical terminology shall be that contained in ANSI S1.l "Acoustical Terminology".
ANSI: American National Standards Institute or its successor bodies.
ARI: Air-Conditioning and Refrigeration Institute or its successor bodies.
ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning Engineers or its successor bodies.
ASTM: American Society for Testing Materials or its successor bodies.
DECIBEL: A unit for measuring the volume of a sound, equal to the logarithm of the ratio of the intensity of the sound to the intensity of an arbitrarily chosen standard sound; abbreviated "dB".
DISCRETE TONE: A discrete tone is a sound wave whose instantaneous sound pressure varies essentially as a simple sinusoidal function of the time.
FLUCTUATING NOISE: A fluctuating noise is a noise whose sound pressure level varies significantly but does not equal the ambient environmental level more than once during the period of observation.
IMPULSIVE NOISE: Impulsive noise is characterized by brief excursions of sound pressure (acoustic impulses which significantly exceed the ambient environmental sound pressure. The duration of a single impulse is usually less than one second.
INTERMITTENT NOISE: An intermittent noise is a noise whose sound pressure level equals the ambient environmental level two (2) or more times during the period of observation. The period of time during which the level of the noise remains at an essentially constant value different from that of the ambient is on the order of one second or more.
IEC: International Electrotechnical Commission or its successor bodies.
ISO: International Organization for Standardization or its successor bodies.
MOTOR VEHICLE: A motor vehicle is any passenger vehicle, truck, truck-trailer, trailer or semi-trailer propelled or drawn by mechanical power.
NONSTEADY NOISE: A nonsteady noise is a noise whose level shifts significantly during the period of observation.
PERIOD OF OBSERVATION: The period of observation is the time interval during which acoustical data are obtained. The period of observation is determined by the characteristics of the noise being measured and should also be at least ten (10) times as long as the response time of the instrumentation. The greater the variance in indicated sound level, the longer must be the observation time for a given expected accuracy of the measurement.
SAE: Society of Automotive Engineers or its successor bodies.
SOUND LEVEL (Noise Level): For air-borne sound, sound level (noise level) is a weighted sound pressure level, obtained by the use of metering characteristics and the A-weighing as specified in the referenced standards (Section 1.3). When the A-weighing is employed, it must be indicated.
SOUND PRESSURE LEVEL: The sound pressure level, in decibels, of a sound is twenty (20) times the logarithm to the base ten (10) of the ratio of the pressure of the sound to the reference sound pressure. Unless otherwise specified, the effective (rms) pressure is to be understood.
The reference sound pressure is 20 uN/M2.
STEADY NOISE: A noise whose level remains essentially constant (i.e., fluctuations are negligibly small) during the period of observation is a steady noise.