2.

The AAD shall have acoustic characteristics (spectral distribution of the acoustic energy sound pressure level) and mechanical characteristics such than it can satisfy the following tests, in the order indicated. 2.1. Measurement of sound characteristics 2.1.1. The AAD should, preferably, be tested in an anechoic environment. Alternatively, it may be tested in a semi-anechoic chamber or in an open space. In this case, precautions shall be taken to avoid reflections from the ground within the measuring area (for instance by erecting a set of absorbing screens). Compliance with the spherical divergence to a limit of 1 dB within a hemisphere of not less than 5 m radius, up to the maximum frequency to be measured, especially in the measuring direction and at the height of the apparatus and the microphone, shall be checked. The ambient noise level shall be at least 10 dB lower than the sound pressure level to be measured. The device to be tested and the microphone shall be placed at the same height. This height shall be between 1,15 and 1,25 m. The axis of maximum sensitivity of the microphone shall coincide with the direction of the maximum sound level of the device. The microphone shall be so placed that its diaphragm is at a distance of 2 ± 0,01 m from the plane of the sound outlet of the device. In the case of devices with several outlets, the distance shall be determined in relation to the plane of the nearest outlet to the microphone. 2.1.2. The measurements of the sound pressure levels shall be made with a class 1 precision sound level meter conforming to the specifications of IEC Publication No 651, first edition (1979). All measurements shall be made using the time constant ‘F’. The measurement of the overall sound pressure level shall be made using the weighting curve A. The spectrum of the sound emitted shall be measured according to the Fourier transform of the acoustic signal. Alternatively one-third octave filters conforming to the specifications of IEC Publication No 225, first edition (1966) may be used: in this case, the sound pressure level in the mid-band frequency 2 500 Hz shall be determined by adding the quadratic means of the sound pressures in the one-third mid-band frequencies 2 000, 2 500 and 3 150 Hz. In every case, only the Fourier transform method shall be regarded as a reference method. 2.1.3. The AAD shall be supplied with current, as appropriate, at the following voltages: 2.1.3.1. in the case of AAD supplied with direct current, at one of the test voltages of 6,5, 13 or 26 volts measured at the terminal of the electric power source and corresponding respectively to rated voltages of 6, 12 or 24 volts; 2.1.3.2. in the case of AAD supplied with alternating current, the current shall be supplied by an electric generator of the type normally used with this type of AAD. The acoustic characteristics of the AAD shall be recorded for electric generator speeds corresponding to 50 %, 75 % and 100 % of the maximum speed indicated by the manufacturer of the generator for continuous operation. During this test, no other electrical load shall be imposed on the electric generator. The endurance test described in item 3 shall be carried out at a speed indicated by the manufacturer of the equipment and selected from the above range. 2.1.4. If a rectified current source is used for the tests of an AAD supplied with direct current, the alternating component of the voltage measured at its terminals, when the warning devices are in operation, shall not be more than 0,1 volt, peak to peak. 2.1.5. For AAD supplied with direct current, the resistance of the connecting leads, including terminals and contacts, shall be as close as possible to: — 0,05 ohms for a 6 volt circuit, — 0,10 ohms for a 12 volt circuit, — 0,20 ohms for a 24 volt circuit. 2.1.6. The device shall be rigidly mounted, using the part or parts provided by the manufacturer, on a support whose mass is at least 10 times that of the device and not less than 30 kg. In addition, arrangements must be made to ensure that reflexions on the sides of the support and its own vibrations have not appreciable affect on the measuring results. 2.1.7. Under the conditions set forth above, the sound-pressure level weighted in accordance with curve A shall not exceed 118 dB(A). 2.1.7.1. In addition, the sound pressure level in the frequency band 1 800 to 3 500 Hz shall be greater than that of any component of a frequency above 3 500 Hz and in any event equal to or greater than 105 dB (A). 2.1.8. The specifications indicated above shall also be met by a device subjected to the endurance test referred to in item 3 below, with the supply voltage varying between 115 % and 95 % of its rated voltage for AAD supplied with direct current or, for AAD supplied with alternating current, between 50 % and 100 % of the maximum speed of the generator indicated by the manufacturer for continuous operation. 2.1.9. The time lapse between the moment of activation and the moment at which the sound reaches the minimum level laid down in item 2.1.7 shall not exceed 0,2 seconds, measured in an ambient temperature of 20 ± 5 °C. This provision shall apply in particular to pneumatically or electro-pneumatically operated devices. 2.1.10. Devices which are pneumatically or electro-pneumatically operated shall, with the pneumatic circuit arranged in accordance with the manufacturer's specification, have the same acoustic performance as that required for electrically operated audible AAD. 2.1.11. In the case of multiple-tone devices in which each sound-emitting unit is capable of functioning independently, the minimum values specified above shall be obtained when each of the constituent units is operated separately. The maximum value of the overall sound level shall not be exceeded when all the constituent units are operated simultaneously.