A new technique of measurement of airborne sound insulation by means of adaptive processing

Abstract

In situ measurement of the airborne sound insulation, according to the ISO 140 Part IV specifications, needs the sound level pressures taken in the source room and in the receiving room, and the background noise level in this last room. Whenever the receiving room presents a great sound insulation, a high sound pressure level excitation is required in the source room in order to guarantee the appropriated margin over the background noise level. This higher sound pressure level is not ever attainable due to the limitations of the conventional sound sources. This procedure describes a new technique of measurement of the airborne sound insulation using a classical adaptive filter configuration that separates the background noise from the excitation sound in the receiving room so that a lower power excitation level can be used. Also, due to the possibility to obtain simultaneously and during a single measurement process the receiving sound pressure level and the background noise level, this technique allows to measure the actual background noise instead of a prior or post estimation of this magnitude once the receiving room level is measured.