6.

TESTING PROCEDURES AND PERFORMANCE STANDARDS FOR SOUND SIGNAL APPLIANCES

6.1

WHISTLES

6.1.1

Samples

Samples submitted for testing shall be representative of the devices as regularly manufactured and marketed.

6.1.2

Power Source

Samples must be powered in the same manner as specified by the manufacturer.  If tolerances are allowed in the powered source the device shall be tested at the tolerance extremes.

.1

Test shall be carried out either in an anechoic chamber large enough to meet the requirements of measurement of sound power at 70 Hz or may be carried out in open fields (grass surface) with the device at least 3 metres above the field surface.

.2

The test location should be proven by obtaining sound level readings at various distances to prove that the field in use obeys the inverse square law.

.3

If an area outdoors is used, readings should also be taken with the measuring microphone and sound device at various heights above the ground to show that a further increase in height does not alter the sound pressure level.

.1

The equipment used shall be a sound level meter with an incorporated 1/3-octave band filter (or with an external 1/3-octave filter) which complies with ANSI S1.14 - 1971, IEC 179, BS 4197 (Sound level meters) and ANSI S1.11 - 1971, IEC 225, BS 2475 (Filters).

.2

The measuring system must have valid calibration, supplied by a national standards laboratory.

.4

If measurements are made outdoors, care must be exercised to ensure that calibration accuracy is maintained under humid conditions.

6.1.5

.1

All of the following readings must be taken within the field where the inverse square law is valid.

.2

As some of the frequencies specified in Annex III do not coincide with 1/3-octave band centre frequencies, care must be exercised in selecting the appropriate 1/3-octave band.

.4

When measuring sound pressure levels for the specified frequencies the following bands shall be selected:

Note:  It would also be permissible to rotate the measuringmicrophone through 360 degrees around a stationary whistle while maintaining a constant horizontal plane passing through the centre of the whistle and staying within the field where the inverse square law is valid.  The distance from the centre of the whistle to the microphone must be recorded for each station.

.5

The dB(A) readings may be required every 15 degrees up to ±45 degrees from ahead and every 30 degrees for the remaining 270 degrees.  However, if the data exhibits a large standard deviation it may be necessary to increase the number of readings.

.6

The dB(A) readings shall be reduced to an equivalent distance at 110 dB(A) and 100 dB(A); the angular position shall also be reported.