title: Free-field correction values for Interacoustics DD 45 supra-aural audiometric earphones.
abstract: OBJECTIVE
  This paper reports free-field correction values for the Interacoustics DD 45 audiometric earphone. The free-field correction values for earphones provide the loudness based equivalence to loudspeaker presentation. Correction values are especially used for the calibration of audiometric equipment for speech audiometry performed with headphones. Calibration values may be found in, e.g. the ISO 389 series of standards.
  
  
  METHODS
  The free-field correction values were determined by means of loudness balance measurements of one-third octave noises (centre frequencies 125 Hz to 8000 Hz) presented alternately from a loudspeaker in a free field and from the earphones. The procedure was essentially in accordance with the free-field frequency response procedure described in IEC 60268-7: Headphones and earphones.
  
  
  METHODS
  Four earphones and 14 test subjects.
  
  
  RESULTS
  Free field correction values are reported for the acoustic coupler IEC 60318-3 (NBS 9-A) and for the ear simulator IEC 60318-1. The results are in good agreement with the results of another independent investigation.
  
  
  CONCLUSIONS
  The reported free-field correction values may be used as part of the basis for future standardization of the DD 45 earphone.
authors.affiliation: Department of Electrical Engineering, Hearing Systems, Technical University of Denmark, Lyngby, Denmark. tp@elektro.dtu.dk
authors.forename: Torben
authors.initials: T
authors.lastname: Poulsen
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001302:Audiometry, Speech / Q000295:instrumentation* / Q000592:standards; D002138:Calibration; D004867:Equipment Design; D005260:Female; D006801:Humans; D008144:Loudness Perception; D008297:Male; D008422:Materials Testing; D011312:Pressure; D011571:Psychoacoustics; D013065:Speech Intelligibility; D013067:Speech Perception; D014160:Transducers, Pressure / Q000592:standards