New innovation to measure wind turbine noise

Published: 24 March 2020 - 2:03 p.m.
By: Baset Asaba

The Boundary-Layer Microphone GF 1 is a new measuring equipment especially designed to record sound emissions at Wind Power Stations according to IEC/EN 61400-11.

The boundary GF 1 and the weatherproof power supply unit WN 1 are specifically developed extensions in order to record the sound emission of wind power stations with measuring microphones.

Additionally, the GF 1 is suitable for determining emission-relevant sound power levels in open spaces, e.g. measurements at power stations, construction sites, filtration and cooling plants among others.

Due to the Operation near the ground, unwanted influences on the measurement results by reflections from the ground are avoided. Measurements are largely independent of the position of measurement and the composition of the ground.

The lower wind speed near the ground causes a further reduction in wind-generated noise at the microphone.

Due to the acoustic effect of the sound-reflecting boundary surface, the microphone sensitivity increases by 6 dB as inherent to its functional principle. Thus, an overall improvement of the signal-to-noise ratio of approx. 46 dB can be achieved.

As measuring microphone element, class 1 measuring microphones are suitable, which consist of measuring microphone cartridges with a frequency range from 20 Hz to 10 kHz, a dehumidifier adaptor and a measuring microphone pre-amplifier with 200 V or IEPE supply.

The WN 1 is a weatherproof power supply unit with the measuring microphone power supply unit MN 921. It provides an operating voltage for conventional measuring microphones (7-pin LEMO ®) as well as for IEPE measuring microphones. It can be operated with accumulators, batteries or mains voltage. The amplification of the microphone signal can be set using a rotary switch. The integrated cable driver allows a transmission of the microphone signals over a cable length of up to 100 m.

The structural design of the GF 1 allows a simple calibration with a sound calibrator. With the divisible ground plate and the secondary windscreen reduced as far as possible, transportation in a compact transport case is possible. With the impregnated secondary windscreen, the groundplate coated with varnish and the weatherproof power supply unit, GF 1 and WN 1 form a weatherproof System for the standard-conforming sound emission measurement of wind power stations.

The 1/2” measuring microphone preamplifier type MV 203 is a high-impedance transducer for 1/2" condenser measuring microphone capsules.

The MV 203 permits sound level measurements with a dynamic range from 11 dB up to 168 dB. The preamplifier has a low output impedance. This renders a good driver capability possible even for long cables. The preamplifier is equipped with a heater resistor preventing a possible condensation under extremely climatic conditions.

The Adaptor A 63.1 allows 1” condenser measuring microphone capsules to be mounted on the 1/2” preamplifier and the Adaptor A 67 makes the same for the 1/4” condenser measuring microphone capsules possible. The thread of the preamplifier confirms to the international standard according to IEC 61094.

The measuring microphone preamplifier MV 203 is designed for sound level meters of IEC Type 1 according to IEC 61672.

The dehumidifier TA 202 is mounted between a ½“- measuring microphone capsule (the capillary for the equalization of the static air pressure is to behind), f. i. MK 202 and MK 221, and a 1/2” – microphone preamplifier.

The TA 202 contains silica gel and effectively removes humidity from the air in the microphone capsule. A small window in the case of the dehumidifier allows to control the humidity of the silica gel. The silica gel changes its colour. By heating for some hours at maximum + 130 °C, the gel is easily dried out again.

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