Sound effects

A sensor that measures localised sonic cavitation could be used to monitor and improve the quality of numerous production processes, according to its developers at the

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Ultrasonic cavitation is used to produce consistent crystalline pharmaceuticals and chemicals, clean printed circuit boards, aerospace and automotive components and sterilise medical equipment. It occurs when sound waves are passed through a fluid to oscillate bubbles of dissolved gas, causing them to implode and so generating heat and localised chemical effects.

Mark Hodnett, senior researcher at NPL, said that ultrasonic cleaning has been used in a variety of manufacturing sectors for more than 50 years.

'In industries using it for cleaning, frequencies of the order of 20 to 40kHz are fired into the fluid and excite millions of these bubbles, which then undergo this implosion process next to the surface of whatever piece is in the vessel to be cleaned,' he added. 'When this happens you get microscopic jets produced from these bubbles that dive down onto the surface that are able to remove particulate and dirt contaminants. It is effectively an acoustic scrubbing process.