There are a few possible ways to measure and calculate sound power of your test object. Depending on the product, the acoustic test environment available and the amount of test that have to be carried out you must choose one of these three methods:
Sound intensity measurement method is used for in situ measurements and product engineering. Optimal for measuring a larger noise emitting object in any acoustic environment, with a steady background noise. Learn more about Sound Intensity.
Reverberation Sound power measurement method as described in ISO 3741 are particularly suitable when performing measurements of small machines where the sound emitted is predominantly steady in character. The testing is quite quick and affordable, and it provides engineering-grade results. Even the test lab; the reverbant test room, is quite east to set up as most unfurnished hard-walled rooms can comply to the requirements set in the standard.
Free-field Sound power measurement method for determining noise emitted from a product placed in an acoustically open area. Such an open area can be a quiet open-air space far from human activity, or an anechoic chamber/ laboratory.
The Nor850 multi-channel software for sound power testing offers an intuitive and direct solution for a complete measurement and reporting according to relevant ISO standards. The system automatically calculates the Sound Power of the product and display the resulting sound power frequency spectrum.
Examples of products that requires a LWA noise label on units sold in EU:
- EC/2000/14 covers noise emission by equipment for outdoor use; includes products like lawnmowers, hedge trimmers, saw machines, chain saws, compactors, drills, hydraulic hammers, leaf blowers, power generators, snow removing machines, water pumps, and more.
- ISO 6395 covers earth-moving machinery; like dozers, scrapers, graders and many more.
- ISO 7779 / ISO 9296 / ECMA 74 covers information technology, computers, and telecommunication equipment; includes products like PC’s, typewriters, printers, copiers, fax machines, etc.
- IEC 60704 Household electrical appliances; includes products like vacuum cleaners, fan heaters, dishwashers, washing machines, electric shavers, electric hair care appliances, ovens, microwaves, refrigerators, etc.
These product specific standards all refers to the general test and measurement standards of acoustics:
Pressure based measurement methods:
Standard – Test environment – Accuracy
ISO 3741 – Reverberant room – Precision
ISO 3743-1 – Hard-wall room – Engineering
ISO 3743-2 – Reverberation room – Engineering
ISO 3744 – Free-field over reflective plane – Engineering
ISO 3745 – Semi- or anechoic room – recision
ISO 3746 – Semi- or anechoic room – Survey
ISO 3747 – Reverberant field in-situ – Engineering/Survey
Direct method: ISO 3741, 3743-2, 3744, 3745, 3746
Comparison method: ISO 3743-1, 3747
Sound Intensity: ISO 9614
The comparison method requires the use of a calibrated Reference Sound Source like the Norsonic Nor278.