The geniohyoid and the role of the strap muscles in pitch control

Abstract

Many investigators have noted a relationship between strap-muscle activity and pitch lowering, but there does not seem to be any single generally accepted theory to account for this connection. The articularly effect of strap-muscle contraction will depend in part on what other forces are acting on the hyoid bone; therefore, in the context of a general EMG investigation of English intonation, we recorded from a supraphyoidal muscle, the geniohyoid. In our data, the three strap muscles show nearly identical patterns of activity; as a group, their activity shows a strong negative correlation with the activity of the geniohyoid. By comparing these patterns of activity for otherwise identical utterances with systematically varied pitch contours, we are able to sort out the effects resulting from tongue and jaw movements from the activity specifically related to pitch control, and to arrive at an hypothesis concerning the effects on vocal-cord tension of the forces applied, by these extrinsic muscles, to the hyoid bond and the thyroid cartilage.