Technical Booklet G Resistance to the Passage of Sound·Page 119·B2.5
Sound source stability during measurements
Once the sound source spectrum has been correctly adjusted, all measurements in source and receiving rooms must be made without moving the sound source or changing its output level.
It is essential that all measurements made in the source and receiving rooms to determine a level difference should be made without moving the sound source or changing the output level of the sound source, once its spectrum has been correctly adjusted (where necessary).
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