The standard specifies two test methods for the determination of the sound reduction index in the field for quality testing of exteroir building elements. (i.e. windows, doors, ventilation elements, facades, roofs). The two methods differ from each otherby the sound source used for excitation of the test object. The test object is excited either by loudspeaker noise or by the existing traffic noise, incident on the test object. In both cases the sound average pressure level in front of the test object is determined at a distance less than 10 mm or >= 2 m. In case of measurement with traffic noise the sound pressure levels on both sides of the test object are measured simultaneously.