ISO 14257 pdf download – Acoustics -Measurement and parametricdescription of spatial sound distributioncurves in workrooms for evaluation of their acoustical performance.
5 Measurement of the spatial sound distribution curve
5.1 Specifications regarding the sound source used for the test
5.1.1 Performance requirements to be met by the source
Part of the requwements br i’eberence sound sources accordng to ISO ó2ti are more sLriiiyri1 mar’ riry Iuq me purposes of this International Standard. Some characteristics of the reference sound source, however. must meet more stringent requirements for measurements to be wi accordance with this International Standard. Annex A therefore specifies the requirements for a reference sound source for the purposes of this International Standard.
5.1.2 Calibration and verification of the sound power of the source
The sound source shall be calibrated in octave and one-third-octave frequency bands in accordance with ISO 6926 Table 2 indicates the acoustical environments to be used for sound power and directivity determinations. depending on the position of the source in normal use, for calibration and verification purposes. The method for determining the directional ctiaracteristics of the Sound source is specified in annex A, Checks shall be done in octave bands. Intervals between checks depend on experience gathered with the source system used.
If the source system Is used rather frequently, It Is recommended to determine Its sound power level In octave bands every 3 months or more frequently until there are at least six Individual measurement results. Later on, time intervals between checks may be longer.
NOTE The purpose of the determinahon of the spatial Sound stñbuflon curve may not require knowledge of the sound power level of the sou,ce This is the case, for example. 4ien the acoustical pertonnance of a workroom (see d.ause 6) is evaluated usig oy the rate of spatial decay of sound pressure levels per distance doiMling (see 3.5).
5.1.3 Location of the source
For measurement of me spatial sound distribution jrve, the acoustical centre of the sound source shall be located
— either as close as possible to the floor, or
at a height above the floor of more than 0,5 m.
A source is considered as being close to me floor ((its acoustical centre is at a height less than or equal to 0,5 m.
The acoustical centre of the source shall be located at least 3 m away from any wall and any reflecting object other than the floor. If this requirement cannot be fulfilled because of the room dimensions, the distance used for the test shall be recorded and reported
5.1.4 Sound power versus background noise
The sound power of the source shall be such that, (or all distances and for all octave bands for which the spatial sound distribution curve is to be measured, the sound pressure level due to the source s at least 10 dB higher than the background noise from other sources. If, at a given measurement point and in a given octave band, the sound pressure level, when the source used for the test is in operation, is less than 10 dB but more than 6 dB higher than background noise, a background noise correction determined as specified in ISO 3744 shall be made.
5.2 Measurement Instrumentation
Sound pressure levels in each octave band and at each microphone position shall be measured using a class 1 sound level meter in compliance with IEC 60651 or a class 1 integrating-averaging sound level meter in compliance with IEC 60804. The miorophone shall be omnidirectional (taking into account any supplementary equipment connected to it). Octave-band filters shal comply with lEG 61260.
If the signal Is recorded (using, for example, analog or digital recorders) for oil-line processing, It shall be ensured that the instrumentation as a whole complies with the above-mentioned requirements.
ISO 14257 pdf download – Acoustics -Measurement and parametricdescription of spatial sound distributioncurves in workrooms for evaluation of their acoustical performance
