IEC 60704-1-2021 pdf download.Household and similar electrical appliances – Test code for the determination of airborne acoustical noise – Part 1: General requirements.
4 Measurement methods and acoustical environments 4.1 General This document is concerned with objective methods of engineering accuracy grade 2 in accordance with ISO 1 2001 :1 996 for determining sound power levels L W , expressed in decibels (dB), with reference to a sound power of one picowatt (1 pW), of airborne acoustical noise within the specified frequency range of interest (generally including the octave-bands with centre frequencies from 1 25 Hz to 8 000 Hz), and for prescribed operating conditions of the appliance to be measured. Methods for determining sound power levels with precision accuracy grade 1 in accordance with ISO 1 2001 :1 996, as specified for example in ISO 3741 and ISO 3745, are not included in this document.
They may, however, be applied if the appropriate test environment and instrumentation are available. NOTE 1 The noise values obtained under the described conditions of this document will not necessarily correspond to the noise experienced under the operational conditions of practical use. NOTE 2 For quality control during production etc., simplified methods can be appropriate. For noise reduction purposes, other measurement methods employing, for example, narrow-band analysis or intensity techniques usually have to be applied. These methods are not covered by this document.
The total noise emitted by machinery or equipment and radiated in all directions to the space surrounding the machine can be characterized by the sound power of the machine. Within the accuracy range of this document, the sound power of a machine is basically independent of the environment in which the machine is installed Therefore, the concept of sound power level has been chosen for expressing the noise emission of appliances for household and similar purposes. The preferred noise emission quantity is the A-weighted sound power level, L WA , in dB (re 1 pW). According to this document, two principal methods exist, the direct method and the comparison method, as described in 4.2 and 4.3. These two methods can be used alternatively.
Different types of environments, as described in 4.4, may be used. A part of the IEC 60704-2 series may, if necessary, exclude one or several combinations among those available.
4.2 Direct method The direct method can be used only for measurements in qualified test environments in accordance with ISO 3744:201 0 for free field conditions over reflecting plane(s), and in accordance with ISO 3743-2:201 8 for special reverberation test rooms.
With this method, the sound power level is determined
– in free field conditions over reflecting plane(s), from time-averaged sound pressure levels (on a mean-square basis) over the measurement surface and from the area of the measurement surface, S, or
– in reverberation and special reverberation test rooms, from averaged sound pressure levels, and from the reverberation time and the volume of the test room.
If for a measurement in a free field, reverberation or special reverberation room is not possible because the appliance cannot be placed or operated in such an environment, the intensity method in accordance with ISO 961 4-1 :1 993, ISO 961 4-2:1 996, and ISO 961 4-3:2002 shall be applied. For the intensity method, the standard deviations given in the parts of the IEC 60704-2 series and IEC 60704-3:201 9 are not applicable unless stated explicitly.
These methods yield results expressed in A-weighted sound power levels (and in octave- or 1 /3 octave-band sound power levels, if required) that are calculated directly from measured sound pressure levels.
NOTE This method can also be used in conjunction with more precise methods, such as those given in ISO 3741 and ISO 3745.IEC 60704-1 pdf download.