scope:

This part of IEC 60704 specifies methods for measuring airborne acoustical noise emitted by electric refrigerators, frozen-food storage cabinets, food freezers and their combinations for household and similar uses, supplied from the mains or from batteries.

The term "similar use" means "use under conditions similar to those in a household", for example, in cafés, restaurants, hotels, and similar establishments.

This standard does not apply to appliances, equipment or machines designed exclusively for industrial or commercial purposes.

This standard is concerned with objective methods of engineering accuracy (engineering method, grade 2, according to IS0 2204) for determining sound power levels, (LW expressed in decibels with reference to a sound power of 1 pW, of airborne acoustical noise within the specified frequency range of interest, and for specified operating conditions of the appliance to be measured.

The frequency range of interest includes the octave bands with centre frequencies between 125 Hz and 8 000 Hz (this interval being, for practical reasons, narrower than the frequency range of audible sound).

The following sound power levels are used:

- A-weighted sound power level, L_WA;

- octave band sound power levels, L_WOct.

In general, the methods described are specified for appliances operated with no operator present.

The noise measurements are made while the compressors are running.

Requirements as to an indication of the noise emission values are not the subject of this standard.

NOTE 1 The uncertainties of measurement according to this standard usually result, for A-weighted sound power levels, in standard deviations generally not exceeding approximately 2 dB, provided that the noise spectrum does not contain pronounced discrete frequencies; if it does, the magnitude of the uncertainties will be larger. The standard deviations referred to reflect the cumulative effects of all causes of measurement uncertainties, excluding variations in the noise level of the appliance from test to test.

NOTE 2 The noise values obtained under the conditions described in this standard will not necessarily correspond with the noise experienced under the operational conditions of practical use (see 6.4.1).

NOTE 3 For quality control during production, etc., simplified methods may be appropriate. For noise control purposes (for example, development of quieter appliances, insulation of equipment, etc.), other measurement methods using, for example, narrow-band frequency analysis will usually have to be applied. These methods are not covered in this standard.

This standard does not include methods for determining sound power levels with precision accuracy (precision method, grade 1, according to IS0 2204) specified, for example, in IS0 3741, IS0 3742 and IS0 3745; they may, however, be applied if the appropriate instrumentation and test environments are available.