| Résumé | Laboratory and working standard microphones are calibrated using the current international standard based on the reciprocity method yielding the pressure and free-field sensitivities of the device under test. The typical uncertainties associated with reciprocity are so low that they exceed the requirements of the most demanding end-user applications, and so the drive for improvement from an uncertainty perspective is low. However, reciprocity also limits the microphone technologies that can be calibrated as it is only applicable to condenser microphones of specific characteristics, standards and dimensions. Microphones, in the broader sense, vary with regards to dimensional and even technological perspectives and in addition are used in free-field conditions. As such, a potential new primary standard that can accommodate and calibrate any microphone for airborne and audible frequencies has been developed based on the photon correlation method in free-field conditions. In this case, the pressure of a propagating sound field in a fully anechoic chamber is measured remotely for a range of specific frequencies, either set or even user-defined. Following, the device under test is placed at the same point of the propagating sound and its electrical output is combined with the optically measured pressure to yield the device sensitivity directly and in an absolute manner. This paper discusses the properties and numerical contributions of potential uncertainty factors associated with the proposed new standard. |
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