Wideband active noise control for open-ear headphones via low-delay acoustic design with a coaxial loudspeaker

Open-ear headphones preserve environmental awareness but provide little passive attenuation, so broadband feedforward active noise control (ANC) is required. This paper presents a controlled measured-path offline study of a wideband ANC design using one device in one dummy-head wearing configuration, based on a design-oriented secondary-path delay budget. A coaxial offset 2-way secondary source with a tweeter placed in front of a woofer is used, and the control bands are assigned on the basis of frequency-dependent delay characteristics, where the woofer is favored at low frequencies because of its smaller mechanical delay, while the tweeter is favored at higher frequencies because of its shorter acoustic propagation delay. We investigated two implementations: one for a dual-filter setup and the other for a single-filter setup. In this idealized linear measured-path evaluation under controlled assumptions, the two-driver configurations increased band-limited noise-power reduction for broadband pink noise relative to the unfiltered single-driver baselines. At the nominal controlled virtual electronic delay of 104 µs, the background dual-filter condition Du-BpHp-Bg and the single-filter condition Xo-BpHp achieved 8.01 and 7.58 dB reductions from 1 0 0 H z t o 2 0 0 0 H z , respectively, compared with 5.94 dB for Wf-Bp and 5.02 dB for Tw-Bp. For the tested device and wearing configuration, these results indicate that a design-oriented delay budget can support driver-band allocation for broadband feedforward ANC in open-ear headphones.