Geneva, 15 July 2015
On June 17, 2015 the 109th Ecma General Assembly approved the Technical Report:
- ECMA TR/107 1st edition – An alternate background noise correction sensitive to the steadiness of background noise
As Dr. Charles Oppenheimer (Hewlett-Packard Acoustics and Vibration Expert) explained this Technical Report will be beneficial to laboratories testing quiet products in a laboratory in which the background sound level is close to the product sound level. This Technical Report describes an alternate background noise correction that depends not only on mean background noise proximity to measured source levels, like the standard background noise corrections of ISO 3741, ISO 3744, ISO 3745, and ISO 11201, but also on the steadiness of the background noise. Like the standard background noise corrections, the alternate background noise correction tends to increase as the background noise level approaches the measured source level, but the alternate background noise correction also increases with the steadiness of the background noise, unlike the standard background noise corrections.
Using the alternative procedure in this Technical Report would result in lower reported sound levels for quiet products tested in a laboratory when the background level is close to the measured source level (which includes both product and background contributions). The reported sound level for a low noise product can be more than 3 dB lower than what can be reported according to the procedures currently contained ECMA-74 when the measured source level is less than the background level or 1 – 2 dB lower when the measured source level is approximately equal to the background sound level.
It is intended that this Technical Report will be used by acoustic testing laboratories before it is proposed as an alternative method for background noise corrections in the basic ISO sound power standards (ISO 3741, ISO 3744, ISO 3745, and ISO 11201) and in ECMA-74. Users are encouraged to report any problems discovered or possible improvements.
For more information: please contact Dr. Istvan Sebestyen, Secretary General of Ecma International. Email: firstname.lastname@example.org.