Appliance Design - November 2007 - (Page 35)

QUALITY & STANDARDS will measure the magnitude and direction of sound across the plane of the microphone and from there the noise can be tracked back to the surface of the product. “It is like shooting an arrow and knowing the angle of the flight,” he says. “Because I can track the waves back to the surface of the product, I can predict where the noise is coming from.” This is one of the tests that laboratories such as MSC and Owens Corning can do, but not the only type of test. While not all labs can do every test, some tests that can be undertaken include airflow resistance of acoustical materials (ASTM C522), normal incidence sound impedance and absorption (ASTM E1050), diffuse field sound absorption (ASTM C423), sound transmission loss (ASTM E90), sound power (ISO 3741/ANSI S12.31 or ISO 3745/ANSI S12.35) and sound Intensity (ISO 9614). Owens Corning Acoustic Research Center can conduct these material and other product tests. Two of the most often run material tests at Owens Corning are the impedance tube testing and the airflow resistance testing. The impedance tube test is a fast way of generating the absorption characteristics of a material or material system. In this test, researchers use a tube about 4 inches in diameter. A speaker is at one end and a rigid hard wall is on the other end. The sample is mounted against the wall. Sound is generated with a speaker and it flows down the tube. The sound energy goes through the material, hits the rigid wall and is reflected back. Microphones measure the sound that is flowing down the tube and the sound energy reflected back and the difference between the two is what was absorbed by the sample. The airflow resistance test works on the idea that sound energy can be turned into heat through viscous flow loss as sound waves move through the porous material. The determination of this property measures the ability of the material to dissipate acoustic energy. For example, noise from a dishwasher is often muted with a blanket. The goal is to ensure that the right amount of flow resistance is designed into that blanket material to match the performance requirements of that product. The test blows air through a material at a velocity that maintains laminar flow and pressure behind the material develops and is measured. The backpressure is directly proportional to the resistance to flow within that material and the flow resistivity can be calculated from that. “Ultimately, from flow resistivity, we can predict the sound absorption from that material,” says Herreman. In short, a good acoustic lab can provide an OEM with a wealth of information about the noise level and sound quality of their products, but in order to optimize the use of such facilities, OEMs should have some clearly defined objectives. And, as with any testing whose results may lead to a product design change, it is better to find solutions earlier in the design process than later. < For more information, enter: R.H Lyon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 Or email: lyoncorp@lyoncorp.com Material Sciences Corp. . . . . . . . . . . . . . . . . . . . . . . 308 Or email: Jeffrey.Vellines@matsci.com Owens Corning Acoustic Research Center . . . . . . . . 309 Or email: Kevin.herreman@owenscorning.com For more Information Enter 113 www.applianceDESIGN.com applianceDESIGN November 2007 35 http://www.dsmotor.com http://www.oshore.com http://www.dsmotor.com http://www.appliancedesign.com

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Appliance Design - November 2007 Contents Editorial Shipments/Forecasts News Watch Today’s LEDs are Brighter and More Colorful than Previous Versions, Allowing Designers More Opportunities to Improve and Differentiate Their Products. When Converting from CCFL to LED Backlights in LCD Panels, New Driving Methods are Needed. Electrowetting Technology Allows Displays to be Designed in an Extensive Range of Colors. Noise Problems are Not Always Easy to Find or Fix, but Acoustic Labs Can Help Designers Ferret Out the “Good” Noise from the “Bad.” A New Sanitization Protocol for Clothes Washers Combines the Best of Three Well-Established Provisions to Ensure Efficiency, Quality and Safety. Stricter EMC Requirements Raise the Bar for Appliances with Electronic Controls and Require Testing to New Levels. Despite Added Cost and Complexity, Gas-Modulating Systems have Migrated from Large-Scale Boiler Applications to Smaller Residential and Commercial Furnaces and Appliances. A New Treatment Technology Hardens the Surface of Light Alloys such as Aluminum and Magnesium and Expands Their Potential Applications. DesignMart Advertiser’s Index Association Report: AHAM

Appliance Design - November 2007

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