LAUSR

The term ‘multimodal’ typically refers to the combination of two or more sensory modalities; however, through the advancement of technology, modality variations within specific sensory systems are being discovered and compared in regards to physiological perception and response. The ongoing evaluation of air vs bone conduction auditory perception modalities is one such comparison. Despite an increased awareness of the potential benefits of utilizing bone conduction pathways, a complete understanding of the human auditory system, more specifically, the relationship between air conducted and bone conducted sound remains a critical deficiency hindering the development of advanced multimodal auditory displays. Conduction equivalency ratios (CERs), which were defined as the difference in sound intensity levels (in dB) between equally loud signals transmitted in air conduction (AC) (sound field) and bone conduction (BC) modes provided a link between these two modes of hearing by determining the relationship between spectral content of AC and BC sound. The current report aims to describe, in depth, the establishment of such CERs at three BC transducer contact locations on a listener’s head over a range of audible frequencies presented over three signal intensities within a controlled free-field listening environment. Results indicated the AC–BC relationship is not unique and depends on sound intensity, frequency, and BC transducer location. In addition, in terms of head sensitivity, results support similar findings which indicate that the Mastoid and Condyle locations can be considered interchangeable in terms of their frequency-related sensitivity while the Forehead was found to be considerably less sensitive compared to the other locations.