ISO 14257:2001 pdf download

ISO 14257:2001 pdf download.Acoustics – Measurement and parametric description of spatial sound distribution curves in workrooms for evaluation of their acoustical performance.
NOTE 2 When the room is large enough, there can be several possibilities regarding the choice of paths. Two of them are of special relevance depending on the purpose of the measurements, as follows.
a) Determination of several spatial sound distribution curves along the longitudinal and lateral axis of the room in different contiguous zones of it, e.g. when the purpose is evaluation of the acoustical performance of the room (see clause 6) in the middle region in each of these zones. This is of particular interest in the case of large workrooms whose acoustical performance varies from one zone to another due to spatial variations of the room architecture and/or sound absorption properties.
b) Determination of one spatial sound distribution curve for the room along its longitudinal axis and one along its lateral axis. This is of particular interest in the case of large workrooms with homogeneous architecture and absorbing properties for which it is desired to know the acoustical performance.
5.4 Measurement procedure
If possible, measurements shall be carried out with all machines, ventilation system, high-pressure pipework leading through the room, etc. being inoperative except for the sound source used for the test.
The sound source used for the test shall fulfil the requirements of 5.1 and shall be positioned precisely with its acoustical centre as specified in 5.1 .3.
The room under test shall be under its normal operating conditions (normal fittings in terms of type, volume and location in the room; doors and windows closed if this corresponds to the normal operating conditions).
It shall be verified that the requirements regarding background noise given in 5.1.4 are met. If necessary, background noise corrections shall be made according to 5.1 .4.
With the sound source used for the test in operation, the sound pressure level shall be measured at the discrete points located on the measurement path(s), as specified in 5.3, for the six octave bands from 125 Hz to 4 000 Hz.
The overall measurement time may be kept short (so that there is only a short interruption of activity of the workroom) by the use of recording equipment. In this case, the signal shall be recorded without any frequency filtering and the spectral analysis shall be performed later in the laboratory for each measurement point. The dynamic behaviour of the recording equipment shall be taken into account. As a rule, it is recommended to use a pre-amplifier with calibrated decibel ranges.
If several locations of the source used for the test fulfil the requirements of this International Standard and if the purpose of the test is the evaluation of the acoustical performance of the room (see clause 6), the location retained shall be, if possible, in the zone of the room where the noisiest machines are or will be located.
NOTE For a given workroom, results of the measurements described above can be influenced by the type and sound power uncertainty of the sound source used for the test, and by the position and direction of the measurement path. The specifications given in this International Standard ensure that the uncertainty of the measurement method is kept within an acceptable range. Quantitative information on the accuracy of the measurement method cannot presently be given.
However, the following maximum values of the uncertainty for A-weighted levels could be expected for tests carried out under repeatability conditions (same source, same height and orientation of the source, same path, same height of the measurement path, same number and position of microphones, same instrumentation, same operator, unchanged acoustical environment):
5.5 Representation of the measured data
The spatial sound distribution curve shall be drawn into a diagram as shown in Figure 1. The distance drawn on the abscissa is the distance from the microphone to the acoustical centre of the source. Values of D shall be tabulated as shown in Table 4.