Natural Listening over Headphones in Augmented Reality Using Adaptive Filtering Techniques

Augmented reality (AR), which composes of virtual and real world environments, is becoming one of the major topics of research interest due to the advent of wearable devices. Today, AR is commonly used as assistive display to enhance the perception of reality in education, gaming, navigation, sports, entertainment, simulators, etc. However, most of the past works have mainly concentrated on the visual aspects of AR. Auditory events are one of the essential components in human perceptions in daily life but the augmented reality solutions have been lacking in this regard till now compared to visual aspects. Therefore, there is a need of natural listening in AR systems to give a holistic experience to the user. A new headphones configuration is presented in this work with two pairs of binaural microphones attached to headphones (one internal and one external microphone on each side). This paper focuses on enabling natural listening using open headphones employing adaptive filtering techniques to equalize the headset such that virtual sources are perceived as close as possible to sounds emanating from the physical sources. This would also require a superposition of virtual sources with the physical sound sources, as well as ambience. Modified versions of the filtered-x normalized least mean square algorithm (FxNLMS) are proposed in the paper to converge faster to the optimum solution as compared to the conventional FxNLMS. Measurements are carried out with open structure type headphones to evaluate their performance. Subjective test was conducted using individualized binaural room impulse responses (BRIRs) to evaluate the perceptual similarity between real and virtual sounds.