Biomedical subjects

Boaz Rafaely

Publications and source records attributed to Boaz Rafaely.

4 recordsLinked to original sources

PubMed2003

Experimental investigation of spatial correlation in broadband reverberant sound fields.

The spatial correlation has previously been investigated for tonal and narrow-band sound fields. This letter presents an experimental investigation of the spatial correlation coefficients in a reverberation chamber driven by broadband signals. The main objective is to verify recent theoretical results for broadband spatial correlation in diffuse sound fields. Experimental results show good agreement with theoretical predictions when the frequency band of the sound field is entirely above the Schroeder frequency.

Journal Article↗

PubMed2002

Combined feedback-feedforward active noise-reducing headset--the effect of the acoustics on broadband performance.

Active noise-reducing headsets that employ analog feedback control and provide good broadband attenuation are commercially available for a wide range of applications. Recent studies have explored the integration of an adaptive digital feedforward controller with the analog feedback controller to provide additional attenuation of periodic noise components. This paper presents an experimental study of such a combined control system, but with both feedback- and feedforward controllers attenuating broadband noise. Good performance is demonstrated in a reverberant sound field, while under direct sound-field conditions the attenuation performance of the feedforward controller is shown to be dependent on head position. The paper concludes with an analysis of the forward path delay showing how the passive attenuation mechanism improves broadband performance.

Computers↗

PubMed2002

Novel active noise-reducing headset using earshell vibration control.

Active noise-reducing (ANR) headsets are available commercially in applications varying from aviation communication to consumer audio. Current ANR systems use passive attenuation at high frequencies and loudspeaker-based active noise control at low frequencies to achieve broadband noise reduction. This paper presents a novel ANR headset in which the external noise transmitted to the user's ear via earshell vibration is reduced by controlling the vibration of the earshell using force actuators acting against an inertial mass or the earshell headband. Model-based theoretical analysis using velocity feedback control showed that current piezoelectric actuators provide sufficient force but require lower stiffness for improved low-frequency performance. Control simulations based on experimental data from a laboratory headset showed that good performance can potentially be achieved in practice by a robust feedback controller, while a single-frequency real-time control experiment verified that noise reduction can be achieved using earshell vibration control.

Ear Protective Devices↗

PubMed2002

Sweet spot size of virtual acoustic imaging systems at asymmetric listener locations.

Virtual acoustic imaging systems are effective when the listener's head location is close to the head location assumed when the system was designed. The "sweet spot" refers to the spatial bubble of head location in which the system is still effective. Some of the previous work investigating the "stereo dipole" acoustic imaging system shows that for the traditional on-axis listener location the "sweet spot" is about +/-5 cm for lateral head translations. Larger head movements than this require an update of the virtual acoustic imaging filters. The interest here is the "sweet spot" size at off-axis asymmetric listener locations or an understanding of how often one needs to update the filters to ensure the listener perceives a stable virtual image as they move. The examination of the off-axis "sweet spot" size comprises a theoretical acoustic analysis, computer simulations, and a subjective study. The simulations and subjective evaluation both demonstrate that the width of tolerable lateral head translations is comparable for the symmetric on-axis listener location and asymmetric listener locations that are as far as 25 cm off-axis.

Acoustics↗