A new artificial ear for telephone use

Abstract

Up until today the CCITT has recommended provisionally the use of the IEC artificial ear as an acoustic load to measure the sensitivity/frequency curve for telephone receivers. This artificial ear was obtained for audiometric requirements. In the telephone use the acoustic leak greatly influences the acoustic load. In this paper we describe an automatic system for the impedance measurement in module and phase versus frequency of the human ear measured during the telephone use. The measurements were obtained with a telephone handset in a normal use. The telephone handset was the acoustic source. A microphone probe at the handset auricle center drew the acoustic pressure. Measurements were made on 50 subjects at two different sound levels. After obtaining the electric simultation of the acoustic impedance shape we built a prototype of a new artificial ear for telephone use. The results obtained using constructed prototypes are shown. Measurements were carried out of the response curves of three different telephone receivers inserted in three types of handsets. The results obtained using human subjects are compared with those obtained using the IEC artificial ear and the new artificial ear for telephone use.