Document ID: chunk:federal_register_of_legislation:F2018L01513:body:0:p7
Version: federal_register_of_legislation:F2018L01513
Segment Type: other
Provision Reference: 
Character Range: 21109–24131

sound; its acoustic spectrum shall not vary substantially during its operation.

 For audible warning devices, audible warning system, multiple audible warning system supplied with alternating current, this requirement shall apply only at constant generator speed, within the range specified in paragraph 6.3.4.2.

               The type approval tests shall be carried out on two samples of each type submitted by the manufacturer for approval; both the samples shall be subjected to all the tests and must conform to the technical specifications laid down.

6.1.2. The audible warning device, audible warning system, multiple audible warning system shall have acoustic characteristics (spectral distribution of the acoustic energy, sound pressure level) and mechanical characteristics such that it passes, in the order indicated, the tests according to paragraphs 6.3. and 6.4.

6.2. Measuring instruments

6.2.1. Acoustic measurements
6.2.1.1. When no general statement or conclusion can be made about conformance of the sound level meter model to the full specifications of IEC 61672-1:2013,[3] 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 as described in IEC 61672-3:2013.3 Measurements shall be carried out using the "fast" response of the acoustic measurement instrument and the "A" weighting curve as described in IEC 61672-1:20133. 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.
 When measurements of the sound pressures in the one-third mid-band frequencies 2,000, 2,500 and 3,150 Hz are carried out for one-third octaves, the instrumentation shall meet all requirements of IEC 61260-1-2014, class 1. 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.
When measuring the rated sound frequency (or frequencies), the digital sound recording system shall have at least a 16 bit quantization. The average auto power spectrum shall be determined, using a Hanning window and at least 66.6 per cent overlap averages.
 The instruments shall be maintained and calibrated in accordance with the instructions of the instrument manufacturer.

              6.2.1.2.  Calibration of the entire Acoustic Measurement System for a Measurement Session
               At the beginning and at the end of every measurement session the entire measurement system shall be checked by means of a sound calibrator that fulfils the requirements for sound calibrators of at least precision Class 1 according to IEC 60942:2003. Without any further adjustment the difference between the readings of two consecutive checks shall be less than or equal to 0.5 dB.
               If this value is exceeded, the results of the measurements obtained after the