ASME PTC 36 pdf free download

ASME PTC 36 pdf free download Measurement of Industrial Noise Performance Test Codes
2-1 DEFINITIONS
For definitions or descriptions of any other terms, please refer to ANSI/ASA S1.1.absorption: see sound absorption.
acoustic, acoustical: qualifying adjectives meaning containing, producing, arising from, actuated by, related to, or ass0-ciated with sound.Acoustic is used when the term being qualified designates something that has the properties, dimen-sions, or physical characteristics associated with sound waves.Acoustical is used when the term being qualified does notexplicitly designate something that has such properties, dimensions,or physical characteristics.
airborne sound: sound that arrives at the point of interest by propagation through air.
ambient noise: all-encompassing sound at a given place, usually a composite of sounds from many sources. When theintent is to measure or record a specific source or signal, the ambient noise does not include sounds of interest.A-weighted sound level: a sound level to which an A-weighting electrical filter, or its equivalent, has been applied thatconforms with ANSI/ASA S1.4/Part 1/IEC 61672-1.This filter attenuates low- and high-frequency sound.
background noise: total of all sources of interference in a system used for the production, detection, measurement, orrecording of a signal, independent of the presence of the signal.Ambient sound detected, measured,or recorded with thesignal is part of the background noise.Included in the definition of background noise is the interference resulting fromprimary electric power supplies that are commonly described as hum.
decibel (dB): unit of the level, L, of a power or power-like quantity when the base of the logarithm is 10.
L = 10log1o(Q/Qo), dB
where
Q = is the power-like quantity concernedo = is the corresponding reference value
discrete frequency a sound wave, the instantaneous sound pressure of which is a simple sinusoidal function of time.far field: the region not included in the near field.
filter: a device for separating sound signal on the basis of frequency.
free field: the region where the sound-pressure level decreases 6 dB from a given point source for each doubling ofdistance from thesource.Thisregion will existifthe soundsource isin the free field or when in anenclosure, the enclosureis large enough so that the reverberant field had not been reached first. The acoustic field should be sufficiently distantfrom a distributed sound source so that the sound pressure decreases linearly with increasing distance(neglectingreflections, refraction, and absorption). Figure 2-1-1 depicts in a general way the application of this terminology.
p(r)~1/r
where
p = pressure
r = distance from source
Practically, the sound-pressure level decreases 6 dB with each doubling of distance from the acoustic source.When making measurements inside buildings, the near field and reverberant field frequently overlap,eliminating thefree field. See Figure 2-1-1.
frequency:The rate of change with time of the instantaneous phase of a sinefunction divided by 2T,with thedimensions ofcycles per second or hertz (Hz).
hertz (Hz): see frequency.
level: in acoustics, logarithm of the ratio of a variable quantity to a corresponding reference value of the same units.Thebase of the logarithm, is assumed to be 10.Unless otherwise specified, the reference value and the kind of level are to bespecified. See also ANSI/ASA S1.8.
microphone: electroacoustic transducer that produces electric signals when excited by acoustic signals.
near field:the part ofthe sound source field that lies between the source and the farfield.In this region,the sound pressuredoes not decrease 6 dB for each doubling of distance from the source.
octave band: sound contained within a restricted frequency band where the highest frequency is twice the lowestfrequency.Octave and one-third octave (octave band divided into three parts) band measurements are found on acous-tical instruments. See also ANSI/ASA S1.6.
reflecting surface: an acoustically non-absorptive (acoustically hard) surface, as opposed to an acoustically absorptive(acoustically soft) surface.
reverberant field: the sound in an enclosed or partially enclosed space that has been reflected repeatedly or continuouslyfrom the boundaries.
sound: an oscillation in an elastic medium that can produce the sensation of hearing.Also,the sensation of hearing causedby a pressure oscillation.
sound absorption: reduction in sound energy as it reflects off a surface.
sound level: measured in decibels, a frequency-weighted sound-pressure levelobtained using a sound-level meter whoseweighting characteristics are specified in ANSI/ASA S1.4/Part 1/IEC 61672-1.
sound-level meter a device that is used to measure sound-pressure level, functioning in accordance with the standardspecifications for sound-level meters established by ANSI/ASAS1.4/Part 1/IEC61672-1and filters established by ANSI/ASA S1.11/Part 1/IEC 61260-1 (see Section 7).
sound-power level (L.w): ten times the logarithm to the base ten of the ratio of the sound power produced by the soundsource to the reference power of 10-12 watts (w.
sound-pressure level (L.): ten times the logarithm to the base ten of the ratio of the square of the sound pressure of thesound under consideration to the square of the standard reference pressure. The standard reference pressure is 20micropascals (Pa) or its equivalent,2 × 10-5 N/m2.
tone: a sound wave capable of exciting an auditory sensation of pitch (see also discrete frequency).