ANSI/ASA S3.7-1995 (R2008)

The physical configuration and acoustical performance of couplers for calibration of supra-aural and insert earphones are specified. The standard which is a revision of S3.7-1973, describes a family of 6.0 cm^3 and 2.0 cm^3 couplers, and provides information on the methods for coupler calibration of the respective supra-aural and insert earphones. The family of 6.0 cm^3 couplers includes the NBS 9-A Coupler for testing supra-aural earphones (ANSI S3.6-1989), the Type-1 Earphone coupler for testing supra-aural earphones without cushions, and the IEC Coupler for supra-aural earphones. The family of 2.0 cm^3 earphone couplers includes the HA-1 Coupler for earphones mounted in an ear insert or an ear insert connected to an earphone, the HA-2 Coupler for tests in which an acoustic tube connects an earphone to an ear mold or ear insert, the HA-3 Coupler for testing the modular portion of a hearing aid, and an HA-4 Coupler for testing post auricular hearing aids or eyeglass hearing aids assumed to have a uniform 1.93 cm diameter sound path.