The effect of talker-listener angle on word intelligibility. II. In an open field

Two experiments were conducted to study the effects on speech intelligibility of talker angle and listener angle and the distance between talker and listener under free-field conditions. Some findings were that (1) speech intelligibility falls off with distance in a manner consistent with a 3 dB per distance doubled fall-off in speech sound pressure level; (2) the intelligibility in a broad arc from −45° to +45° in front of the talker was essentially equal; (3) the effect of turning the listener 15° to 75° away from the talker was a mean gain of about 4% or a gain equivalent to about 3.5 m in distance; (4) the observed directional aspect of intelligibility agreed quite well with SPL measurements made by other investigators around the heads of a model and a human; and (5) the effects of distance and wind in this study were in general agreement with the results of previous studies.