Surround by Sound: A Review of Spatial Audio Recording and Reproduction

In this article, a systematic overview of various recording and reproduction techniques for spatial audio is presented. While binaural recording and rendering is designed to resemble the human two-ear auditory system and reproduce sounds specifically for a listener’s two ears, soundfield recording and reproduction using a large number of microphones and loudspeakers replicate an acoustic scene within a region. These two fundamentally different types of techniques are discussed in the paper. A recent popular area, multi-zone reproduction, is also briefly reviewed in the paper. The paper is concluded with a discussion of the current state of the field and open problemsThe authors acknowledge National Natural Science Foundation of China (NSFC) No. 61671380 and Australian Research Council Discovery Scheme DE 150100363

Implementation of manifold bridge tuning for noise control of an automotive intake system.

The considerable effort invested by automobile manufacturers to attenuate various noise sources within the passenger compartment has resulted in other sources such as induction noise having become more noticeable. This study was undertaken to investigate the feasability of using a non conventional noise cancellation technique to improve the acoustic performance of the induction system by introducing exhaust noise into the intake system through a manifold bridge. The effectiveness of this technique was first investigated using Ricardo Wave, a computational, engine simulation, software program. Using a one-dimensional, finite-difference approach to analyse the dynamics of the pressure waves, mass flows, and energy losses within the ducts, an optimized bridge configuration was determined. A physical model incorporating the design of the optimized bridge was installed and tested on a motored engine for comparison to the numerical results. The realized attenuation of induction noise due to the manifold bridge was evaluated using 1/12th octave frequency spectra and three-dimensional colour maps of both the unmodified and bridged engine for steady state and transient engine cases. A sound quality analysis was also performed using various psychoacoustic metrics including loudness, sharpness, roughness and fluctuation strength. Both the numerical and experimental models demonstrated reductions in the overall sound level measured at the intake opening with the experimental results being more favourable. While the results of the sound quality analysis correlated well between the numerical and experimental models, the success of the bridging technique was somewhat ambiguous, depending on the sound quality metric used. As with the traditional analysis techniques, the reported loudness was lower for the numerical and experimental bridged engines. Sharpness was found not to be a relevant metric in this study due to a lack of high frequency content to the noise. Depending on the engine speed, values for roughness and fluctuation strength were either improved or diminished with the implementation of the manifold bridge. For the conditions tested, implementation of the manifold bridge has demonstrated promise. Before it can be declared commercially viable, however, further considerations such as the effects of exhaust gas recirculation and fired engine tests, are warranted.Dept. of Mechanical, Automotive, and Materials Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .N68. Source: Dissertation Abstracts International, Volume: 66-11, Section: B, page: 6097. Thesis (Ph.D.)--University of Windsor (Canada), 2005

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

A Uniform Method of Mechanical Disturbance Torque Measurement and Reduction for the Seeker Gimbal in the Assembly Process

In the manufacturing process of seekers, the reduction of disturbance torques (DTs) is a critical but time-consuming work. The innovation of the paper is to present a uniform method to measure and reduce mechanical DTs during gimbal’s assembly process. Firstly, the relationships between assembly parameters and DTs are established and analyzed by theoretical model. And then, a measuring system is established to measure the driven torque of the gimbal’s torque motor. With the goal of stabilizing and minimizing the driven torque, all assembly parameters relating to DTs could be adjusted. Through the proof of a lot of experiments, this proposed method could reduce the bias and fluctuation of these mechanical DTs. This method could also be used for the mechanical DTs reduction of most similar productions and improve the quality and efficiency during their system assembly process

Effects of Fluctuating Salinity, Nutritional State, and Temperature on Leptasterias Spp. From Little Port Walter, Alaska.

The effects of fluctuating salinity, nutritional state, and temperature on activity, oxygen consumption, feeding, and growth rates were analyzed on seasonally collected Leptasterias spp. (Echinodermata: Asteroidea) from Little Port Walter, AK. Leptasterias aspera and L. epichlora were collected on June 10, 1994, divided into size groups, and perivisceral fluid osmolality was measured every three hours during a 12 h 30-10-30‰S fluctuating cycle. The perivisceral fluid osmolality of larger individuals fluctuated less than that of smaller sea stars. The perivisceral fluid osmolality of small and large Leptasterias spp. closely tracks the ambient water osmolality during tidal cycles. Leptasterias spp. were collected on August 31, 1994 and separated into three nutritional treatment groups and analyzed over 31 days. Starved individuals had lower oxygen consumption rates than fed individuals. Feeding and starvation data suggest that Leptasterias spp. from Little Port Walter can survive beyond 31 days with a negative energy budget. For studies of temperature acclimation, Leptasterias spp. were collected at the annual temperature minimum (1°C; 19 November 1995, 27 February 1998) and the annual temperature maximum (12°C; 1 September 1996, 2 July 1997). Individuals from seasonal collections were step-wise acclimated (2°C every two days) or acutely exposed to 5°C, 7.5°C, 10°C, 12.5°C, 15°C, 17.5°C, 20°C, or 22.5°C. The 28-day LC50 of winter acclimatized, acutely exposed animals were 8 and 10°C lower than summer acclimatized, step-wise acclimated and summer acclimatized, acutely exposed individuals, respectively. Acute exposure and step-wise acclimation to experimental temperatures above the normal environmental maximum, 12.2°C, resulted in suppressed feeding and elevated oxygen consumption rates. Leptasterias spp. exist near the upper limit of capacity adaptation when environmental temperatures reach the annual summer maximum and undergo seasonal acclimatization to water temperature. Leptasterias spp. are adapted to withstand sublethal temperature shifts, which occur both seasonally and diurnally in the intertidal zone. Activity only partially correlated with environmental changes (temperature exposure, fluctuating salinity, and nutritional state of the animal). Reduced salinity negatively affected activity in Leptasterias spp. Activity coefficients varied with starved and fed feeding regimes, but were not significantly different between feeding treatments or time. Activity coefficients of Leptasterias spp. did not vary significantly with temperature

Will the Three Gorges Dam affect the underwater light climate of Vallisneria spiralis L. and food habitat of Siberian crane in Poyang Lake?

Almost 95% of the entire population of the Siberian crane (Grus leucogeranus) winter in Poyang Lake, China, where they forage on the tubers of the submerged aquatic macrophyte Vallisneria spiralis. The Three Gorges Dam on the Yangtze River may possibly affect this food source of the Siberian crane by affecting the light intensity reaching the top of the V. spiralis canopy. In this study, the photosynthetically active radiation at the top of the V. spiralis canopy (PARtc) in Lake Dahuchi was modeled from 1998 to 2006, and the potential impacts of changes in water level and turbidity on the underwater light climate of V. spiralis were analyzed. PARtc was calculated from incident irradiance while the losses due to reflection at the water surface, absorption, and scattering within the water column were taken into consideration. The results indicated significant differences in PARtc between years. Six years of water level and Secchi disk depth records revealed a seasonal switching of the lake from a turbid state at low water levels in autumn, winter, and spring to a clear state at high water levels during the monsoon in summer. The highest PARtc occurred at intermediate water levels, which were reached when the Yangtze River forces Lake Dahuchi out of its turbid state in early summer and the water becomes clear. The intended operation of the Three Gorges Dam, which will increase water levels in May and June, may advance the moment when Lake Dahuchi switches from turbid to clear. We suggest that this might increase production of V. spiralis and possibly improve the food habitat conditions for wintering Siberian crane in Poyang Lake