Receiver-Based Auralization of Broadband Aircraft Flyover Noise Using the NASA Auralization Framework

The NASA Auralization Framework (NAF) consists of a set of dynamic link libraries (DLLs) to facilitate auralization of aircraft noise. Advanced capabilities for synthesis, propagation, and external interfaces are provided by the NAF Advanced Plugin Libraries (APL); a separate set of DLLs that are made accessible through the NAFs plugin architecture. In the typical time domain use case, the sound is first synthesized at the source location based on a source noise definition, and is then propagated in the time domain to a receiver on or near the ground. Alternatively, it may be desirable to synthesize the sound at the receiver, after it has been propagated in the frequency domain, e.g., when the source definition is inaccessible or when alternative propagation methods are needed. Receiver-based auralization requires three new developments in the NAF APL: a component plugin to interpolate the propagated noise spectra as a function of time for input to sound synthesis, and a path finder and path traversal plugin to calculate the effects of the differential propagation path length between the direct and ground reflected rays. This paper describes those developments and demonstrates their use in the auralization of broadband flyover noise

Archaeological Testing of 41BX1131 at O.R. Mitchell Dam, Bexar County, Texas

The Center for Archaeological Research contracted with the Simpson Group to conduct testing of 41BXl131, a prehistoric archaeological site located at the base of O. R. Mitchell Dam, on Medio Creek in southwest Bexar County. The purpose of testing was to determine whether or not the site would be impacted by construction of a spillway in the immediate area. A pedestrian survey identified the extent of surface scatter. Subsequent shovel testing and backhoe trenching determined that the site had no depth, and consisted of a surface scatter only

Resonance tongues and patterns in periodically forced reaction-diffusion systems

Various resonant and near-resonant patterns form in a light-sensitive Belousov-Zhabotinsky (BZ) reaction in response to a spatially-homogeneous time-periodic perturbation with light. The regions (tongues) in the forcing frequency and forcing amplitude parameter plane where resonant patterns form are identified through analysis of the temporal response of the patterns. Resonant and near-resonant responses are distinguished. The unforced BZ reaction shows both spatially-uniform oscillations and rotating spiral waves, while the forced system shows patterns such as standing-wave labyrinths and rotating spiral waves. The patterns depend on the amplitude and frequency of the perturbation, and also on whether the system responds to the forcing near the uniform oscillation frequency or the spiral wave frequency. Numerical simulations of a forced FitzHugh-Nagumo reaction-diffusion model show both resonant and near-resonant patterns similar to the BZ chemical system

Effects of low-intensity blood flow restriction training vs. no blood flow restriction training on measures of aerobic capacity in physically active individuals

Background: Blood flow restriction (BFR) training has become an extremely popular training method over the years. Improvements in measures of aerobic capacity (such as VO2max) are crucial for individuals whom seek to be physically active for longer periods of time. Recent studies have focused on the combination of BFR and aerobic exercise at lower training intensities as an adapted training method for either maintaining or improving measures of aerobic capacity in physically active individuals.Clinical Question: In physically active individuals, is low-intensity blood flow restriction training more effective than no blood flow restriction training at improving measures of aerobic capacity?Methods: A computer-assisted literature search of PubMed, MEDLINE, SPORTDiscus, and EBSCOHost databases (from inception to November 2019) was utilized to identify studies of level 3 evidence or higher that assessed the effect of low-intensity BFR training versus no BFR training on measures of aerobic capacity in physically active individuals. The main outcomes of interest were either pre-post testing assessments of aerobic fitness (such as VO2max or VO2peak) and/or pre-post testing assessments of aerobic performance (such as time to exhaustion).Summary of Key Findings: The search strategy revealed 4 studies that met the inclusion criteria. One study reported that there were no significant improvements in measures of aerobic capacity when using low-intensity BFR training versus not using BFR training (1.96%, p < 0.05), while two studies reported that there in fact were significant improvements in measures of aerobic capacity (VO2max: 6.5%, p < 0.05 and TTE: 15.4%, p < 0.01; VO2max: +9.1± 6.2%, P < 0.001). One study reported that there were significant improvements in aerobic capacity when using low-intensity BFR training versus low-intensity training without BFR (BFR group: 5.6 ± 4.2%, P = 0.006, ES = 0.33; LOW group: 0.4 ± 4.7%, P = 0.75); however, high-intensity training without BFR showed greater improvements in aerobic capacity when compared to low-intensity training with BFR (HIT group: 9.2 ± 6.5%, P = 0.002, ES = 0.9).Clinical Bottom Line: There is moderate evidence to support the use of low-intensity BFR training to improve aerobic capacity in physically active individuals.Strength of Recommendation: Grade B evidence exists that low-intensity BFR training is more effective than no BFR training at improving measures of aerobic capacity in physically active individuals

The Use and Performance of Geogrids in Kentucky

This report will investigate the history and usage of geogrids, a subfamily of geosynthetics, in Kentucky. The American Society for Testing and Materials (ASTM - 1994) has defined a geosynthetic as a planar product manufactured from a polymeric material used with soil, rock, earth, or other geotechnical-related material as an integral part of a civil engineering project, structure, or system. Geogrids, geosynthetics primarily used for reinforcement, are formed by a regular network of tensile elements with apertures of sufficient size to interlock with surrounding fill material. Geogrids are used as reinforcement by adding tensile strength to a soil matrix, thereby providing a more competent structural material. Reinforcement enables embankments to be constructed over very soft foundations and permits the construction of steep slopes and retaining walls

Utilizing Low-Intensity Blood Flow Restriction Training to Improve Aerobic Capacity in Physically Active and Injured Individuals: A Critically Appraised Topic

Purpose: To determine if, in physically active individuals, low-intensity Blood Flow Restriction (BFR) training is more effective than training without BFR at improving measures of aerobic capacity. Methods: A database search was conducted for articles that matched inclusion criteria (minimum level 2 evidence, physically active participants, comparison of low-intensity BFR to no BFR training, comparison of pre-post testing with aerobic fitness or performance, training protocols \u3e2 weeks, studies published after 2010) by two authors and assessed by one using the PEDro scale (a minimum of 5/10 was required) to ensure level 2 quality studies that were then analyzed. Results: Four studies met all inclusion criteria. Three of the studies found significant improvements in aerobic capacity (VO2max) using BFR compared to no BFR. While the fourth study reported significant improvements in time to exertion (TTE) training with BFR, this same study did not find significant improvements in measures of aerobic capacity with BFR training. All compared BFR to non-BFR training. It was noted that high-intensity training without BFR was superior to both low-intensity training with and without BFR with respect to improvements in aerobic capacity. Conclusions: Moderate evidence exists to support the use of low-intensity BFR training to improve measures of aerobic capacity in physically active individuals over not using BRF. Clinicians seeking to maintain aerobic capacity in their patients who are unable, for various reasons, to perform high levels of aerobic activity may find low-intensity BFR training useful as a substitution while still receiving improvements in measures of aerobic capacity

Auralization Architectures for NASA?s Next Generation Aircraft Noise Prediction Program

Aircraft community noise is a significant concern due to continued growth in air traffic, increasingly stringent environmental goals, and operational limitations imposed by airport authorities. The assessment of human response to noise from future aircraft can only be afforded through laboratory testing using simulated flyover noise. Recent work by the authors demonstrated the ability to auralize predicted flyover noise for a state-of-the-art reference aircraft and a future hybrid wing body aircraft concept. This auralization used source noise predictions from NASA's Aircraft NOise Prediction Program (ANOPP) as input. The results from this process demonstrated that auralization based upon system noise predictions is consistent with, and complementary to, system noise predictions alone. To further develop and validate the auralization process, improvements to the interfaces between the synthesis capability and the system noise tools are required. This paper describes the key elements required for accurate noise synthesis and introduces auralization architectures for use with the next-generation ANOPP (ANOPP2). The architectures are built around a new auralization library and its associated Application Programming Interface (API) that utilize ANOPP2 APIs to access data required for auralization. The architectures are designed to make the process of auralizing flyover noise a common element of system noise prediction

The NASA Auralization Framework and Plugin Architecture

NASA has a long history of investigating human response to aircraft flyover noise and in recent years has developed a capability to fully auralize the noise of aircraft during their design. This capability is particularly useful for unconventional designs with noise signatures significantly different from the current fleet. To that end, a flexible software architecture has been developed to facilitate rapid integration of new simulation techniques for noise source synthesis and propagation, and to foster collaboration amongst researchers through a common releasable code base. The NASA Auralization Framework (NAF) is a skeletal framework written in C++ with basic functionalities and a plugin architecture that allows users to mix and match NAF capabilities with their own methods through the development and use of dynamically linked libraries. This paper presents the NAF software architecture and discusses several advanced auralization techniques that have been implemented as plugins to the framework

Acoustic Calibration of the Exterior Effects Room at the NASA Langley Research Center

The Exterior Effects Room (EER) at the NASA Langley Research Center is a 39-seat auditorium built for psychoacoustic studies of aircraft community noise. The original reproduction system employed monaural playback and hence lacked sound localization capability. In an effort to more closely recreate field test conditions, a significant upgrade was undertaken to allow simulation of a three-dimensional audio and visual environment. The 3D audio system consists of 27 mid and high frequency satellite speakers and 4 subwoofers, driven by a real-time audio server running an implementation of Vector Base Amplitude Panning. The audio server is part of a larger simulation system, which controls the audio and visual presentation of recorded and synthesized aircraft flyovers. The focus of this work is on the calibration of the 3D audio system, including gains used in the amplitude panning algorithm, speaker equalization, and absolute gain control. Because the speakers are installed in an irregularly shaped room, the speaker equalization includes time delay and gain compensation due to different mounting distances from the focal point, filtering for color compensation due to different installations (half space, corner, baffled/unbaffled), and cross-over filtering