BS ISO 14878 pdf free download

BS ISO 14878:2015 pdf free download.cycles一Audible warning devices – Technical specification and test methods.
5.1 Instruments for acoustical measurement
5.1.1 General
The apparatus used for measuring the sound pressure level shall be a sound level meter or equivalent measurement system meeting the requirements of class 1 instruments (inclusive of the recommended windscreen, if used). These requirements are described in IEC 61672-1.
The entire measurement system shall be checked by means of a sound calibrator that fulfils the requirements of class I sound calibrators according to IEC 60942.
Measurements shall be carried out using the time weighting “Fm of the acoustic measurement instrument and the A frequency weighting curve also described in IEC 61672-1. When using a system that includes a periodic monitoring of the A-weighted sound pressure level, a reading should be made at a time interval not greater than 30 ms.
The instruments shall be maintained and calibrated in accordance to the instructions of the instrument manufacturer.
When no general statement or conclusion can be made about conformance of the sound level meter model to the full specifications of IEC 61672-1, the apparatus used for measuring the sound pressure level shall be a sound level meter or equivalent measurement system meeting the requirements of class I instruments as described in IEC 61672-3.
NOTE The tests of IEC 61672-3 cover only a limited subset of the specifications in IEC 61672-1 for which the scope is large (temperature range, frequency requirements up to 20 kl-Iz, EMC tests). It is economically impossible to verify the whole IEC 61672-1 standard requirements one each item of a computerized data acquisition systems model.
5.1.2 Calibration
At the beginning and at the end of every measurement session, the entire acoustic measurement system shall be checked by means of a sound calibrator as described in 5J..J.. Without any further adjustment, the difference between the readings shall be less than or equal to 0,5 dB. If this value is exceeded, the results of the measurements obtained after the previous satisfactory check shall be discarded.
5.1.3 Compliance with requirements
Compliance of the sound calibrator with the requirements of IEC 60942 shall be verified once a year. Compliance of the instrumentation system with the requirements of IEC 61672-3 shall be verified at least every two years.
All compliance testing shall be conducted by a laboratory which is authorized to perform calibrations traceable to the appropriate standards.
5.1.4 Meteorological Instrumentation
The meteorological instrumentation used to monitor the environmental conditions during the test shall meet the following specifications:
— ±1 °C or less for a temperature measuring device;
— ±1,0 rn/s for a wind speed-measuring device;
— ±5 hPa for a barometric pressure measuring device;
— ±5 % for a relative humidity measuring device.
6 Acoustical environment, meteorological conditions, and background noise
6.1 Test site
The AWD shall 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).
The test facility shall meet requirements of ISO 26101 with the following qualification criteria and measurement requirement appropriate to this test method as recommended by ISO 26101:
— space to be deemed anechoic shall be at least a 5-metre radius volume;
— test sound source location shall position in the middle of the space to be deemed anechoic, on the floor;
— microphone transverses shall be from the centre of the source to each microphone position;
— the maximum spacing of the measurement points shall depend on the size of the space to be deemed anechoic. A minimum of 10 points shall be used for spatial resolution of measurement;
— qualification band width shall be defined to cover the typical of the spectral range of interest that will be measured. Without any information, it is recommended from 100 Hz to 10 000 Hz;
— generation of sound shall be a broadband noise and a 1/3 octave filter for measurement requirements.
For indoor test site, the test facility shall have a cut-off frequency lower than the frequency of the lowest component of the sound emitted by the AWD under test.
In the vicinity of the microphone, there shall be no obstacle that could influence the acoustic field and no person shall remain between the microphone and the noise source. The meter observer shall be positioned so as not to influence the meter reading.
NOTE It is expected that users of this International Standard will understand that valid measurements can only be made when the cut-off frequency is lower than the lowest frequency of interest. A specific numerical requirement for cut-off frequency is not given due to the range of variation of appropriate cut-off frequencies depending upon the measured article.
6.2 Meteorological conditions
The meteorological instrumentation shall deliver data representative for the test site and shall be positioned adjacent to the test area at a height representative of the height of the measuring microphone.
The measurements shall be made when the ambient air temperature is within the range from 10 °C to
30°C.
The tests shall not be carried out if the wind speed, including gusts, at microphone height exceeds 5 rn/s. during the sound measurement interval.
A value representative of temperature, wind speed and direction, relative humidity, and barometric pressure shall be recorded during the sound measurement interval.BS ISO 14878 pdf download.