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Identify noise sources - in pictures

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article image Measuring noise levels from wind turbines on wind farms.

A UNIQUE "acoustic camera", that produces a digital image overlaid with a colour-coded noise map showing precisely where noise is being emitted, is making its Australian debut during National Manufacturing Week 2006, at Sydney's Darling Harbour until June 2.

The GFaI acoustic camera is being demonstrated at the show by HW Technologies on Stand 2718.

It combines an array of microphones to record sound waves with a digital camera to calculate a noise map, then combines both the acoustic and optical images to produce a graphic and easily understood image showing precisely where the noise is coming from.

The acoustic camera is completely portable, able to be used both inside and externally, and gives a rapid and very accurate diagnosis.

The base configuration consists of a microphone array, a data-recording device, a notebook computer and the software "NoiseImage".

According to Hugo Waibel from HW Technologies, the uses for the acoustic camera are virtually unlimited, and include troubleshooting sources of excessive noise emissions in manufacturing plants, R&D and product development, environmental noise testing and management, through to scientific research and even assistance with threatened species protection.

"A key advantage of the acoustic camera is that it allows noise sources to be identified rapidly and very precisely from the position of the listeners - which is very important - even at distances of several hundred metres," Waibel said.

"This gives many advantages over traditional noise-measuring systems.

"For example, instead of placing microphones in a machine or plant and tediously looking for noise sources, the object as a whole can be included with only a few measurements from the relevant listeners' perspectives.

"Using traditional technology, data from numerous measurement points must be acquired using microphones or vibration transducers."

Waibel gave as an example measuring noise levels from wind turbines on wind farms, which can be cause of community concern due to noise and vibration from misaligned blades.

"This is typically a difficult task, given the size of the object and the danger of rotating blades. Even when this has been done, it remains questionable whether the sources that are found to be the loudest are responsible for the noise exposure in the neighbouring community," he said.

“Then there is always the risk of taking the wrong measures to reduce the noise emissions, since these measures would be based on insufficient (and sometimes inadequate) data. Significant amounts of money can be spent without the desired effect."

Other uses for the acoustic camera have included:

* Identifying where noises are coming from in engines and working machinery.

* Highlighting areas of wind noise in new car design.

* Locating small species of threatened frogs in the wild which could be heard but not easily found.

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