ISO 7240-24:2010 pdf free download – Fire detection and fire alarm systems一 Part 24: Sound-system loudspeakers.
5.4 Horizontal and vertical coverage angles
5.4.1 Object of the test
To check that the horizontal and vertical coverage angles specified by the manufacturer [see 4.5.2 c)] are
achieved.
5.4.2 Test procedure
5.4.2.1 General
Measure the horizontal and vertical coverage angles as described in Annex A.
Use octave band filters centred on 500 Hz, 1 kHz, 2 kHz and 4 kHz.
Perform the measurements by supplying the loudspeaker either
a) with a pink noise signal spread over the full range of frequencies from 89 Hz to 11,2 kHz and analysing the microphone output signal by means of octave band filters centred on 500 Hz, 1 kHz, 2 kHz and 4 kHz; or
b) sequentially with an octave band filtered pink noise signal with centre frequencies of 500 Hz, I kHz, 2 kHz and 4 kHz.
The measurement level should be chosen such that the loudspeaker operates within its linear region.
5.4.2.2 Horizontal coverage angle
Measure the sound pressure level for each octave band at the measuring distance in accordance with Annex A. The measurement value shall be the average RMS value over a period of at least:
— 10 s for the 500 Hz octave band, and
— 3 s for the other octave bands.
Rotate the measuring microphone or the loudspeaker in the horizontal plane in an arc about the reference point to one side until the sound pressure level is —6 dB from that recorded on the reference axis. Then rotate the microphone or the loudspeaker to the opposite side of the reference point until the sound pressure level is -6 dB.
Record the total angular movement in degrees as the horizontal coverage angle for each octave band.
5.4.2.3 Vertical coverage angle
Repeat the procedure as specified in 5.4.2.2 for the vertical plane. Record the total angular movement, expressed in degrees, as the vertical coverage angle for each octave band.
5.4.3 Requirements
The measured horizontal and vertical coverage angles shall be within ± 5° of the values specified by the manufacturer.
5.5 Maximum sound pressure level
5.5.1 Object of the test
To check that the maximum sound pressure level specified by the manufacturer is achieved.
5.5.2 Test procedure
5.5.2.1 General
Measure the maximum sound pressure level as described in Annex A.
The clipped noise at the terminals of the loudspeaker under test shall have a peak-to-RMS ratio of between 1,8 and 2,2.
NOTE Peak-to-RMS ratio is commonly called crest factor.
The power amplifier shall have an output impedance not greater than 1/3 of the rated impedance of the loudspeaker system in accordance with 5.3. The amplifier shall be capable of supplying the loudspeaker with a peak voltage of a sinusoidal signal that is at least 2,2 times the rated noise voltage of the loudspeaker.
Supply the loudspeaker with the simulated program signal at the rated noise power and over the full range of frequencies (from 100 Hz to 10 kHz 1/3 octave bands).
5.5.2.2 Measurement of maximum sound pressure level
Measure the maximum sound pressure level, Lmax, expressed in decibels, by integration over a period of at least 30 s, at the measuring distance, on the reference axis.