Binaural Characterization of Active Noise Cancelling Headphones

Active noise cancelling (ANC) headphones have traditionally been used to protect hearing or to reduce the masking of noise on a desired signal and in these applications the primary goal is to maximize noise attenuation. Increasingly ANC headphones are being used for general sound control, to reduce noise-induced stress, and to aid focus and concentration. In these situations, the quality and naturalness of the remaining sound becomes more important as there is often no desired playback signal to mask artifacts. Fluctuating noise levels or differences in processing between channels can create distracting artifacts or distort the binaural cues used for sound localization and situational awareness. In this work we propose using a binaural measurement apparatus to characterize the uncancelled residual noise measured inside the cavity of ANC headphones. We evaluate total noise reduction, residual noise quality, and preservation of binaural cues. We validate the approach using representative consumer circumaural (over-ear) ANC headphones. Results show similar levels of attenuation and good subjective noise quality for both low-cost and premium devices. Distortion of low frequency time and level difference cues was observed for high cancellation levels, additional work is needed to quantify the impact of these distortions on localization.