Influence of control structure and sound reproduction on the intelligibility of speech in headsets with active noise reduction
Anthony J. Brammer, Donald R. Peterson, Martin G. Cherniack, Subhash Gullapalli · The Journal of the Acoustical Society of America · 2004
A primary requirement for a communication headet is to maintain speech intelligibility under all conditions of use. For headsets equipped with active noise reduction (ANR), the performance of the control system may influence the communication signal reaching the ear. Conversely, the communication signal may perturb the operation of the ANR system. The interaction between the communication and control signals will depend primarily on the control structure, and the electro-acoustic transfer function of the earphone and drive electronics of the communication channel. The effect on speech intelligibility will be described using the speech transmission index, for circumaural headsets employing feedback control with a fixed filter and analog signal processing, an approach commonly used in commercial devices, and one employing adaptive, digital feed-forward control. In each case, the active control systems attempt to control low-frequency noise, as the passive attenuation of the earmuff enclosing the ear substantially reduces noise at frequencies above 500 Hz. Results will be discussed for different environmental noise spectra, and speech-to-noise ratios.