Sound Pressure Minimization at the Ear Drum Using an In-Ear Earpiece with a Feedback ANC Controller Based on the Virtual Microphone Arrangement Approach
* Presenting author
Abstract:
In this work we aim to actively reduce external noise with an in-ear earpiece equipped with two loudspeakers and one inner microphone. The proposed solution aims at minimizing the sound pressure at the ear drum by applying the virtual microphone arrangement (VMA) approach with measured or modelled acoustic paths between the loudspeakers of the earpiece and the ear drum. Using only one of both available loudspeakers (tweeter/woofer), the filter coefficients of a fixed feedback ANC controller are optimized to minimize the power spectral density (PSD) at the ear drum, subject to design and stability constraints. The proposed VMA approach is compared to the classical minimum variance feedback controller, which minimizes the PSD at the inner microphone. Simulation results with diffuse noise show that the VMA approach effectively improves the attenuation magnitude and bandwidth, both when using the tweeter or the woofer. The most important improvements are achieved using the tweeter, where the attenuation bandwidth and magnitude are increased by approx. 550 Hz and 12 dB, respectively. Although the VMA approach causes amplifications beyond the desired maximum amplification of 4 dB for frequencies higher than 4 kHz, this occurs in a frequency region where the earpiece already provides sufficient passive attenuation.