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How should one measure the 'casing-radiated' noise for a single room ventilation unit not intended to be equipped with duct connections?

The emitted casing-radiated noise for ventilation units without duct connections can be measured using the sound intensity method as described in ISO 13347-4. This makes it possible to differentiate the emission of sound from different (partial) surfaces of the casing. Thus, a surface with openings (inlet or outlet) can be subtracted. With high air velocities, some caution must be observed; this can be achieved by using windscreens, observing larger measurement distances, etc.

Please note that the total noise from a non-ducted unit should include the noise emitted from the openings in order to be a usable measure of the sound in a room with the unit installed.

If measurements are taken using only sound pressure methods, testing ducts with efficient silencers may be a remedy for reducing duct noise. However, these may influence the pressure loss /air velocity, and thus the sound made by the fan, etc. This is not a problem when using the sound intensity method. (See also ISO 9614-2).

Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.