Head tracking extends local active control of broadband sound to higher frequencies

Stephen J. Elliott,Woomin Jung,Jordan Cheer

doi:10.1038/s41598-018-23531-y

Stephen J. Elliott, Woomin Jung + Show 1 more

Open Access

https://doi.org/10.1038/s41598-018-23531-y

Copy DOI

Journal: Scientific Reports	Publication Date: Mar 29, 2018
Citations: 32	License type: open-access

Affiliation: University of Southampton

Abstract

Local active sound control systems provide useful reductions in noise within a zone of quiet which only extends to about one tenth of an acoustic wavelength. If active control is required above a few hundred hertz, this generally limits the movement of a listener to unrealistically small changes in head position. We describe a local active sound control system using a fixed array of monitoring microphones, in which the pressures at the ear positions are estimated from these microphone signals using head position information from an optical head tracker. These signals are then actively controlled to give robust attenuation at the ear positions, even as the listener moves their head. Feedforward control provides selective attenuation of noise and broadband attenuation of around 20 dB is measured up to excitation frequencies of 1 kHz under favourable conditions, with head tracking achieved in a few seconds. The active control performance is thus comparable with that achieved with active headphones, but without the listener having anything attached to their head.

Highlights

Active sound control headphones, which can reduce noise levels for frequencies up to about 1 kHz, are widely available, their use is not convenient in many applications
The concept of using head tracking with local control was suggested some time ago[7], and a similar system has recently been described for the active control of tonal noise[11], the results presented here, for the active control of broadband noise, clearly demonstrate the range of frequencies over which such active control is possible
As a benchmark for the best possible performance with this arrangement, control was implemented using the signals from the microphones mounted in the dummy head directly as error signals, with the results shown in Fig. 2(a) and (b)

Summary

Introduction

Active sound control headphones, which can reduce noise levels for frequencies up to about 1 kHz, are widely available, their use is not convenient in many applications. Local active control of sound is possible using loudspeakers and microphones remote from the ears, if virtual sensing algorithms are used[1,2,3,4,5,6,7]. At frequencies above a few hundred hertz, normal changes in head position, of 5 cm or so, will move the ears out of this zone of quiet and effective sound control will be lost. The concept of using head tracking with local control was suggested some time ago[7], and a similar system has recently been described for the active control of tonal noise[11], the results presented here, for the active control of broadband noise, clearly demonstrate the range of frequencies over which such active control is possible.

Objectives

Methods

Results

Conclusion