Investigating sound-field reproduction methods as perceived by bilateral hearing aid users and normal-hearing listeners.

A perceptual study was conducted to investigate the perceived accuracy of two sound-field reproduction approaches when experienced by hearing-impaired (HI) and normal-hearing (NH) listeners. The methods under test were traditional signal-independent Ambisonics reproduction and a parametric signal-dependent alternative, which were both rendered at different Ambisonic orders. The experiment was repeated in two different rooms: (1) an anechoic chamber, where the audio was delivered over an array of 44 loudspeakers; (2) an acoustically-treated listening room with a comparable setup, which may be more easily constructed within clinical settings. Ten bilateral hearing aid users, with mild to moderate symmetric hearing loss, wearing their devices, and 15 NH listeners were asked to rate the methods based upon their perceived similarity to simulated reference conditions. In the majority of cases, the results indicate that the parametric reproduction method was rated as being more similar to the reference conditions than the signal-independent alternative. This trend is evident for both groups, although the variation in responses was notably wider for the HI group. Furthermore, generally similar trends were observed between the two listening environments for the parametric method. The signal-independent approach was instead rated as being more similar to the reference in the listening room.

Enhancing binaural rendering of head-worn microphone arrays through the use of adaptive spatial covariance matching.

In this article, the application of spatial covariance matching is investigated for the task of producing spatially enhanced binaural signals using head-worn microphone arrays. A two-step processing paradigm is followed, whereby an initial estimate of the binaural signals is first produced using one of three suggested binaural rendering approaches. The proposed spatial covariance matching enhancement is then applied to these estimated binaural signals with the intention of producing refined binaural signals that more closely exhibit the correct spatial cues as dictated by the employed sound-field model and associated spatial parameters. It is demonstrated, through objective and subjective evaluations, that the proposed enhancements in the majority of cases produce binaural signals that more closely resemble the spatial characteristics of simulated reference signals when the enhancement is applied to and compared against the three suggested starting binaural rendering approaches. Furthermore, it is shown that the enhancement produces spatially similar output binaural signals when using these three different approaches, thus indicating that the enhancement is general in nature and could, therefore, be employed to enhance the outputs of other similar binaural rendering algorithms.

Spatial post-filter for linear hydrophone arrays with applications to underwater source localisation.

This letter presents a spatial post-filter that can be employed in linear hydrophone arrays, commonly found in sonar systems, for the task of improving the bearing estimation and noise suppression capabilities of traditional beamformers. The proposed filter is computed in the time-frequency domain as the normalised cross-spectral density between two beamformed signals, which are generated by applying conventional beamforming to two adjacent non-overlapping sub-arrays. The evaluation on both simulated and real-world data demonstrates promising performance compared to other popular post-filters in some cases, especially for targets near the end-fire direction and in the presence of uncorrelated interferers or diffuse noise.

Parametric spatial post-filtering utilising high-order circular harmonics with applications to underwater sound-field visualisation.

Beamforming using a circular array of hydrophones may be employed for the task of two-dimensional (2D) underwater sound-field visualisation. In this article, a parametric spatial post-filtering method is proposed, which is specifically intended for applications involving large circular arrays and aims to improve the spatial selectivity of traditional beamformers. In essence, the proposed method is a reformulation of the cross-pattern coherence (CroPaC) spatial post-filter, which involves calculating the normalised cross-spectral density between two signals originating from coincident beamformers. The resulting parameter may be used to sharpen another beamformer steered in the same look-direction, while attenuating ambient noise and interferers from other directions. However, while the original 2D version of the algorithm has been demonstrated to work well with second-order circular harmonic input, it becomes increasingly less suitable with increasing input order. Therefore, the proposed reformulation extends the applicability of CroPaC for much higher orders of circular harmonic input. The method is evaluated with simulated data of a 96-channel circular hydrophone array in three different passive sonar scenarios, where the proposed post-filter is shown to improve the spatial selectivity of both delay-and-sum and minimum-variance distortionless response beamformers.

Superhuman spatial hearing technology for ultrasonic frequencies.

Ultrasonic sources are inaudible to humans, and while digital signal processing techniques are available to bring ultrasonic signals into the audible range, there are currently no systems which also simultaneously permit the listener to localise the sources through spatial hearing. Therefore, we describe a method whereby an in-situ listener with normal binaural hearing can localise ultrasonic sources in real-time; opening-up new applications, such as the monitoring of certain forms of wild life in their habitats and man-made systems. In this work, an array of ultrasonic microphones is mounted to headphones, and the spatial parameters of the ultrasonic sound-field are extracted. A pitch-shifted signal is then rendered to the headphones with spatial properties dictated by the estimated parameters. The processing provides the listener with the spatial cues that would normally occur if the acoustic wave produced by the source were to arrive at the listener having already been pitch-shifted. The results show that the localisation accuracy delivered by the proof-of-concept device implemented here is almost as good as with audible sources, as tested both in the laboratory and under conditions in the field.

Effects of size, cooperativity, and competitive binding on protein positioning on DNA.

Accurate positioning of proteins on chromosomal DNA is crucial for its proper organization as well as gene transcription regulation. Recent experiments revealed existence of periodic patterns of nucleoprotein complexes on DNA, which frequently cannot be explained by sequence-dependent binding of proteins. Previous theoretical studies suggest that such patterns typically emerge as a result of the proteins' volume-exclusion effect. However, the role of other physical factors in patterns' formation, such as the length of DNA, its sequence heterogeneity, and protein binding cooperativity/binding competition to DNA, remains unclear. To address these less understood yet important aspects, we investigated potential effects of these factors on protein positioning on finite-size DNA by using transfer-matrix calculations. It has been found that upon binding to DNA, proteins form oscillatory patterns that span over the length of up to ∼10 times the size of the protein binding site, with the shape of the patterns being strongly dependent on the length of DNA and the proteins' binding cooperativity to DNA. Furthermore, calculations showed that small variations in the proteins' affinity to DNA due to its sequence heterogeneity do not much change the main geometric characteristics of the observed protein patterns. Finally, competition between two different types of proteins for binding to DNA has been found to lead to formation of highly diverse and complex alternating positioning of the two proteins. Altogether, these results provide new insights into the roles of physicochemical properties of proteins, the DNA length, and DNA-binding competition between proteins in formation of protein positioning patterns on DNA.