Characteristics comparison of two audio output devices for augmented audio reality

In this paper, we compared two audio output devices for augmented audio reality applications. In these applications, we plan to use speech annotations on top of the actual ambient environment. Thus, it becomes essential that these audio output devices will be able to deliver intelligible speech annotation along with transparent delivery of the environmental auditory scene. Two candidate devices were compared. The first output was the bone-conduction headphones which can deliver speech by vibrating the skull, while normal hearing is left intact for surrounding noise since these headphones leave the ear canal open. The other is the binaural microphone/earphone combo, which is in a form factor similar to a regular earphone, but integrates a small microphone at the ear canal entry. The input from these microphones can be fed back to the earphone along with the annotation speech. In this paper, we compared the speech intelligibility of speech when competing babble noise is simultaneously given from the surrounding environment. It was found that the bone-conduction headphones can deliver speech at higher intelligibility than the binaural combo. However, with the binaural combo, we found that the ear canal transfer characteristics were altered significantly by closing the ear canal with the earphones. If we employed a compensation filter to account for this transfer function deviation, the resultant speech intelligibility was found to be higher than the bone-conduction headphones. In any case, both of these are found to be acceptable as audio output devices for augmented audio reality applications since both are able to deliver speech at high intelligibility even when significant amount of competing noise is present.