Division 3 SOUND LEVEL MEASUREMENTSF1

United Kingdom Repealed

1. 3.1Audible warning devices must preferably be tested in an anechoic environment. They may alternatively be tested in a semi-anechoic chamber or in a cleared outside space. In this case, precautions must be taken in order to avoid reflections off the ground in the measuring area, e.g. by providing a number of absorbent screens. It must be checked that the spherical distortion is no more than 1 dB within a hemisphere having a radius of at least 5 m up to the maximum frequency to be measured, this mainly being in the direction of measurement and at the height of the device and microphone. The ambient noise must be at least 10 dB lower than the sound pressure levels to be measured.
2. 3.2The measurements of the sound pressure level must involve the use of a class-1 precision sound level meter meeting the requirements of IEC publication No 651, first edition (1979).
3. 3.3The audible warning device must be supplied with one of the following voltages, as appropriate:
4. 3.4Division 3.4
5. 3.5The resistance of the electrical conductor for audible warning devices receiving direct current, including the resistance of the terminals and contacts, must lie as closely as possible to:
6. 3.6Division 3.6
7. 3.7Under the conditions set out above the A-weighted sound level must not exceed the following values:
8. 3.7.1Moreover the sound pressure level within the 1 800—3 550 Hz frequency band must be higher than that of any frequency component above 3 550 Hz, and in any case be at least:
9. 3.7.2Division 3.7.2
10. 3.8Division 3.8
11. 3.9Division 3.9
12. 3.10Division 3.10
13. 3.11Division 3.11