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International audience; Binaural pressures include the cues for auditory localization. The scattering and diffraction of the anatomical structures such as head, pinna and torso modify the pressure spectra at the ears (spectral cue). Head turning changes the binaural pressures (dynamic cue). Both spectral and dynamic cues provide information for front-back and vertical localization. Auditory vertical localization is the consequence of comprehensive processing of multiple localization cues by the high level nervous system. In the case of a real sound source, multiple localization cues provide consistent information, enhancing the accuracy in vertical localization. In some cases of spatial sound reproduction, however, some vertical localization cues may be absent (such as in the case of stable virtual auditory display), error, or even conflicting. Therefore, it is necessary to examine the contribution of spectral and dynamic cues to vertical localization. However, the relative importance of two cues is still unclear. The spectral cue has conventionally been regarded as a dominant one and the contribution of dynamic cue was often neglected. In present work, a psychoacoustic experiment was conducted to investigate the vertical localization in the median plane with conflicting spectral and dynamic cues, so as to examine the relative importance of two cues in vertical localization. A dynamic virtual auditory display (VAD), which was able to detect the three degrees of freedom of head turning and then stimulate the binaural signals as well as their variation with head turning, was used as a tool in the experiment. By modifying the head-related transfer functions (HRTFs) used in the dynamic VAD, binaural signals with conflicting spectral cue and dynamic variation of interaural time difference (ITD) were created. That is, for a target source in the median plane, the magnitudes of binaural signals and their variation with head turning were simulated as if target source was located at an elevation (called spectra-based elevation); while the ITD and its variation with head turning were simulated as if target source is located at another elevation (called ITD variation-based elevation). The resultant binaural signals were presented to subjects by a pair of headphone. The subjects reported the perceived virtual source directions. Eight subjects with normal hearing participated in the experiment. A statistical analysis was applied to the experimental data from all subjects. The statistics of experimental results indicated that, for low-pass filtered noise with cut-off frequency of 3 kHz, the perceived virtual source elevation varies basically consistent with dynamic ITD variation (ITD variation-based elevation), regardless of the spectral cue. For pink noise with full audible bandwidth, conflicting spectral and dynamic cues result in two splitting auditory events or perceived virtual sources at different elevations, rather than a fused auditory event at an elevation. The perceived elevation of the virtual source corresponding to the low-frequency component of stimulus is basically consistent with dynamic ITD variation (ITD variation-based elevation), while the perceived elevation of another virtual source correspond to the high-frequency component of stimulus is basically consistent with the spectral cue (spectra-based elevation). Therefore, the present experiment proved that both dynamic and spectral cues are important to vertical localization. Dynamic cue dominates the vertical localization below the frequency of 3 kHz, and the spectral cue dominates the vertical localization above the frequency of 3 kHz.

Proceedings of the ICA 2019 and EAA Euroregio : 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019 : 9-13 September 2019, Aachen, Germany / proceedings editor: Martin Ochmann, Michael Vorländer, Janina Fels 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019, ICA 2019, Aachen, Germany, 9 Sep 2019 - 13 Sep 2019; Aachen (2019)., Published by Aachen

Proceedings of the ICA 2019 and EAA Euroregio : 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019 : 9-13 September 2019, Aachen, Germany / proceedings editor: Martin Ochmann, Michael Vorländer, Janina Fels 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019, ICA 2019, Aachen, Germany, 9 Sep 2019 - 13 Sep 2019; Aachen (2019)., Published by Aachen

Ambisonics is a series of flexible spatial sound systems based on spatial harmonics decomposition of sound field. It is able to reconstruct sound field accurately within some region and below some frequency limit which are imposed by Shannon-Nyquist spatial sampling theorem and determined by the order of Ambisonics. Above the Shannon-Nyquist limit of spatial sampling, errors occur in the reconstructed sound field, resulting audible artifacts. By using Moore's revised loudness model, the present work analyzes the influence of number of loudspeakers on timbre in horizontal Ambisonics reproduction. The binaural loudness level spectra (BLLS) of Ambisonics reproduction are calculated and then compared with those of target sound field. The results indicate that below the Shannon-Nyquist limit of spatial sampling, the BLLS for Ambisonics reproduction match well with those of target sound field and thus no timbre change occurs. Above the limit, however, the BLLS for Ambisonics reproduction deviate from those of target sound field. The extent of deviation depends on both the direction of target sound field and the number of loudspeakers. Increasing the number of loudspeakers in Ambisonics reproduction may increase the change of BLLS in some case, but may reduce the change of BLLS in some other case.

Ambisonics is a series of spatial sound reproduction system with flexible number of loudspeakers. Based on spatial harmonics decomposition and truncation at various orders, it aims at approximate reconstruction of target sound field within a certain region and below a certain frequency limit. The region and frequency limit are determined by spatial sampling theorem of sound field. The present work evaluates the influence of number of loudspeakers on the errors in binaural pressure spectra for spatial Ambisonics reproduction. Binaural pressures for target sound field and Ambisonics reproduction are calculated and normalized square amplitude error in binaural pressures is used as error index. The results indicate that, for each order Ambisonics reproduction, and when the number of loudspeakers exceeds the low limit, increasing the number of loudspeakers reduces, or at least does not increase the errors in binaural pressures. Around the frequency limit given by spatial sampling theorem, the reduction on the errors in binaural pressures by increasing number of loudspeakers is significant. On the other hand, below or above that frequency limit moderately, the reduction is insignificant in terms of auditory perception.

Heparin has typically been used as a flushing or infusion solution for vascular lines in daily practice. However, several clinical trials have yielded controversial results about the benefits of heparin in maintaining peripheral venous catheters. The present meta-analysis was conducted to evaluate the efficacy of heparin on the patency profiles and complications in peripheral intravenous catheters. PubMed, Embase and Cochrane Central Register of Controlled Trials were searched up to February 2016 for randomized controlled trials comparing heparin with placebo in maintaining peripheral intravenous catheters. Additional studies were retrieved from the reference lists of identified articles. In total 32 eligible studies were included, from which the pooled standard mean difference (SMD), relative risk (RR) and corresponding 95% confidence interval (CI) were calculated. The use of heparin as a continuous infusion significantly prolonged the duration of patency (SMD, 0.90; 95% CI, 0.48-1.32; P

One problem in high speed mobile OFDM (orthogonal frequency division multiplexing) system is the phase noise and Doppler frequency shift caused by the relative motion between transmitter and receiver. Especially the phase noise can induce the subcarrier phase rotation, thus the common phase error (CPE) and inter-subcarrier interference (ICI) produced, which can degrade the system performance seriously. In this paper, we analyze the interference model caused by phase noise and Doppler shift firstly, then joint the frequency shift and phase noise to eatimate the interference factor by inserting pilot symbols, finally we apply the iteration method to eliminate the interference step by step. The simulation results show that this algorithm can improve the bit error rate (BER) performance of high speed mobile OFDM system effectively.