Study of the Effects of Active Noise Cancellation on Music Playback

Technology for automotive active noise cancellation (ANC) such as HARMAN’s Engine Order Cancellation (EOC) system help reduce in-cabin noise levels using a set of error microphones and the vehicle’s built-in audio system to generate anti-noise signals. A major benefit of these systems is that significant reduction in unwanted noise levels in the 20 - 400 Hz range can be achieved without the addition of extra noise control material. However, in the instances where the frequencies of anti-noise signals and music signals overlap, a degradation in the overall music reproduction quality is possible. In this paper, we study the effects of EOC on music playback by applying signal processing and statistical methods to objectively measure degradation in audio content when EOC is active. This study is carried out using production EOC software in a simulation environment. The simulation models the cabin acoustic response from measured vehicles and uses recordings of vehicle noise and music as inputs. For each test case, we simulate in-cabin music playback in the presence of engine noise with and without EOC active. This analysis is performed on a large set of music spanning various genres to maximize the likelihood of matching the listening preferences of our end-users. Finally, we also show that musical interference suppression (MIS) algorithms such as TrueAudio can reduce degradation in music reproduction quality when the frequencies of ANC anti-noise signals and music overlap.