Quality Assurance

The laboratory tests for EN 54-24 voice alarm loudspeakers are the focus of product conformity and place high demands on acoustic properties as well as on the reliability of the voice alarm loudspeakers.

Here is a short overview, for a detailed consideration we recommend obtaining the original text of the standard.

The loudspeaker tests depend on the type of environment in which the loudspeaker is to be used (Type A indoor or Type B outdoor) and ultimately on the characteristics that the manufacturer wishes to attribute to the product in the Declaration of Performance. Essentially, however, the tests and the permitted tolerances are identical for both types of loudspeakers, with a few exceptions.


Performance

The EN 54-24 loudspeaker test series starts with the "performance test", in which the frequency response of each test sample is measured with a measurement signal between 85Hz and 12kHz and compared with the permissible values specified in the standard.

Further extensive acoustic tests follow, such as the measurement of the nominal impedance, the horizontal and vertical dispersion angle, as well as the maximum sound pressure level

Further tests focus on durability, e.g. the nominal noise power is measured after 100 hours of continuous exposure to "pink noise". The sound pressure level of the loudspeaker shall not deviate from the original result by more than ± 3 dB after a rest period.

Temperature

Proof that the loudspeaker functions properly even at high ambient temperatures is also a relevant test criterion. A distinction is made between dry heat (in operation) and dry heat as an endurance test. In the last test, a de-energized sample shall be used to demonstrate that the loudspeaker does not show long-term effects of ageing. Temperatures can reach up to 70 degrees Celsius for outdoor speakers.

In addition to heat tests, cold tests are also carried out, with temperatures as low as -25 degrees Celsius for outdoor speakers. Another particularly demanding test is the test of resistance to an environment with high humidity, where there is an increased risk of condensation. The humidity is kept at a high level between 93-95%, while the temperature varies between 25 and 55 degrees Celsius.

Resistance

But that's not all, in the SO2 corrosion resistance test the loudspeaker is exposed to a sulphur dioxide mixture over a period of 21 days in a climate chamber at 93% humidity. This test impressively simulates the possible exposure to atmospheric contaminants.

Finally, the loudspeaker is also subjected to tests to simulate typical mechanical damage. This is a matter of insensitivity to mechanical impacts as well as robustness against impacts on the surface of the loudspeaker.

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