ASTM C634-13 (R2021) pdf free download.Standard Terminology Relating to Building and Environmental Acoustics.
maximum sound level, LAFMAX,I[dimeIzsionIess], (dB), n—Ten times the common logarithm of the square of the ratio of the largest frequency-weighted and exponential-ti me-weighted (or otherwise time-averaged) sound pressure during the measurement period to the square of the reference-sound- pressure of 20 jiPa. The subscripts designate the frequency weighting (A or C). and time the weighting or averaging (F for fast. S for slow. I for impulse, or a number with proper units to indicate time interval).
Discussion—The time weighting or averaging time must be spedlied. The frequency weighting should he specified; otherwise, A-weighting will be understood.
measurement plan, n—a document formally describing the specific steps to be taken during a measurement, including any unique requirements.
measurement set, n—the set of acoustical measurements and related data obtained at a single measurement location during a specified time interval.
Discussion—The specified time interval may include brief documented periods during which data recording or analysis are paused lir the purpose of eliminating the effects of interference.
metric sabin, [L2], n—the unit of measure of sound absorption in the metre-kilogram-second system of units.
noise isolation class, N IC[diinensio,zless], n—a single-number rating calculated in accordance with Classification E413 using measured values of noise reduction. It provides an estimate of the sound isolation between two enclosed spaces that are acoustically connected by one or more paths.
noise reduction, NR[dimcnsionlessl, n—the difference between the average sound pressure levels either at two well defined locations based on existing conditions, or at a single location before and after some mitigation measure is implemented.
DIscussion—Specific sLandards may use a more restrictive definition related to the difference either between two locations or before and after a mitigation measure, and some standards may require the noise reduction to be measured in specified frequency bands.
noise reduction coefficient, NRC[dimensionless], n—a single- number rating, the average, rounded to the nearest 0.05, of the sound absorption coefficients of a material for the four one-third octave bands at 250 H.. 500 Hz. 1000 Hz. and 2000 Hz, inclusive, measured according to the test method described in Test Method C423.
normal incidence sound absorption coefficient, cx11[dimensionless], n— of a surface, at a specified frequency, the fraction of the perpendicularly incident sound power absorbed or otherwise not reflected.
normal mode, n—of a room, one of the possible ways in which the air in a room, considered as an elastic body, will vibrate naturally when subjected to an acoustical disturbance. With each normal mode is associated a resonance frequency and, in general, a group of wave propagation directions comprising a closed path.ASTM C634 pdf download.