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Brüel & Kjær gets low noise down under

09 December 2008

Brüel & Kjær assist New Zealand based wind farm project

As one of the windiest cities in the Southern hemisphere, Wellington is ideal for wind farming, but the plans for installing up to 68 wind turbines caused locals to raise concerns about the potential noise impact. Local energy provider, Meridian, was asked to monitor background noise at five of its wind farm locations before building of the new site began, but wind turbine noise is notoriously difficult to measure, as the low sound doesn’t trigger sound level monitors.

By using several Noise Management Terminals, from Sound and vibration expert, Brüel & Kjær, Meridian was able to set up timed recordings to carry out its investigation. The equipment used consisted of an Environmental Noise Management Server (Version 2) Type 3642, five Noise Monitoring Terminals Type 3639-E-203 with Weatherproof Microphone Units Type 4198 and Weather Stations MM-0256.

A time trigger recording option was created to capture sound recordings and the data saved as WAV files (instead of MP3) for subsequent tone assessment. In the UK, many Local Authorities receive complaints about low-frequency noise, but subsequent investigations are difficult and time-consuming to make.

With the introduction of modern noise monitoring instruments, such as sound and vibration expert Brüel & Kjær’s 2250 Hand-Held Analyser - with built-in sound recording and logging 1/3rd octave frequency spectrum - the procedure for practical assessment (developed by Drs Moorhouse, Waddington and Adams at Salford University) has been simplified.

An application note outlining how to make these assessments, with sound and vibration expert Brüel & Kjær’s 2250 meter, is available on the company’s UK website: The parameters to be measured: the Leq, 5mins values in each 1/3rd octave frequency band over a frequency range of 10Hz to 160Hz and, the L10,5mins and L90,5mins values in each 1/3rd octave frequency band over a frequency range of 10Hz to 160Hz. and, continuous logging of the short term LAeq values.

It is advisable that the complainant should have the ability to record the actual sound when the noise is present. For details of the required procedure visit Bruel & Kjaer UKs website at:

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Bruel & Kjaer UK