Loudness perception with headphones versus loudspeakers

This study examines whether human loudness perception is influenced by the type of sound source, or determined exclusively by the sound pressure received at the eardrum. The literature contains conflicting views on this issue, particularly for the case of listening to earphones compared to, for example, listening to loudspeakers. To begin with, the paper summarizes the controversial results of earlier experiments. Ambiguities and loose ends worth investigating are pointed out; crucial aspects of experimental design are considered, e.g., the test sound material, various ways of binaural versus monaural presentation, and the psychometric method. Following this, new experiments are proposed. They comprise: (1) subjective equal-loudness comparisons (2-AFC) between various types of headphones and loudspeakers at different locations, and (2) probe-microphone measurements of the corresponding sound pressures in the listener’s ear canals. Finally, first results are presented. As a practical application, consequences to techniques of headphone calibration are discussed.