SEL: sound exposure level SII: speech interference index SIL: speech interference level SLM: sound level meter SPI: speech privacy index SPL: sound pressure level
STI: speech transmission index TTS: temporary threshold shift A1.2 Terms A-weighting: see frequency weighting absorption coefficient: see sound absorption coefficient
acoustical coupler: a cavity of predetermined shape and volume used for the calibration of earphones or microphones in conjunction with a calibrated microphone adapted to measure the sound pressure developed within the cavity anechoic room: a room whose boundaries absorb practically all of the sound incident thereon, thereby providing essentially freefield conditions articulation index (AI): a number (ranging from 0 to 1) which is a measure of the intelligibility of speech- the higher the number the greater the intelligibility. This metric has been replaced by the Speech Intelligibility Index (SII) defined in ANSI S3.5. average sound level: see equivalent continuous sound level background noise: the total noise from all sound sources other than a particular sound that is of interest band: a subsection of the frequency spectrum C-weighting: see frequency weighting coupler: see acoustical coupler day-night level (DNL): the 24 hour equivalent (average) A-weighted sound pressure level. A 10 dBA penalty is incurred between the hours of 10:00 PM and 7:00 AM. The DNL system has been adopted by the U.S. Department of Housing and Urban Development, the Department of Defense, and the Federal Aviation Administration. decibel (dB): a unit of level which denotes the ratio between two quantities that are proportional to power; the number of decibels is 10 times the common logarithm (base 10) of this ratio. diffuse field: a sound field which has statistically uniform energy density and in which the
42 of 58 Spendiarian & Willis Acoustics & Noise Control LLC
12/15/2019
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