It is hypothesized that sound quality metrics, particularly loudness, sharpness, tonality, impulsiveness, fluctuation strength, and roughness, could all be possible indicators of the reported annoyance to helicopter noise. To test this hypothesis, a psychoacoustic was conducted in which subjects rated their levels synthesized sounds. After controlling for previous analysis using linear regression identified sharpness tonality as important factors predicting annoyance, followed by strength....

A matrix methodology similar to that of the finite element method is developed for analysis stress waves in layered solids. Because mass distribution modeled exactly, approach gives exact frequency response each layer. The fast Fourier transform and series are used inversion time/space domain. impact a structured medium with multiple layers demonstrate method. Comparison existing propagator direct global methods show present be computationally more efficient.

The goal of this investigation is to further develop nonlinear modal numerical simulation methods for application geometrically response structures exposed combined high intensity random pressure fluctuations and thermal loadings. study conducted on a flat aluminum beam, which permits comparison results obtained by reduced-order analysis with those from numerically intensive in physical degrees-of-freedom. A uniformly distributed loading first applied investigate the dynamic instability...

The goal of this investigation is to further develop nonlinear modal numerical simulation methods for application geometrically response structures with shallow curvature under random loadings. For reduced order analysis, the basis selection must be capable reflecting coupling in both linear and stiffness. symmetric arch consideration, four categories functions are defined. Those having transverse displacements (ST modes) can designated as dominated (ST-T) modes in-plane (ST-I) modes....

A psychoacoustic test was performed using simulated sounds from a distributed electric propulsion aircraft concept to help understand factors associated with human annoyance. design space spanning the number of high-lift leading edge propellers and their relative operating speeds, inclusive time varying effects motor controller error atmospheric turbulence, considered. It found that mean annoyance response varies in statistically significant manner inclusion effects, but does not differ...

System noise assessments of a state-of-the-art reference aircraft (similar to Boeing 777-200ER with GE90-like turbofan engines) and several hybrid wing–body configurations were recently performed using NASA engine system analysis tools. The sized an equivalent mission as the measurements airframe shielding from series propulsion aeroacoustic experiments. focus this work is auralize flyover best configuration source predictions data based largely on earlier assessments. Here, auralization...

Noise is expected to be a major barrier of unmanned aerial vehicles (UAVs) public acceptance. A noise prediction scheme introduced in this paper and applied specific vehicle configuration, namely, the Greased Lightning-10. Results herein will used demonstrate feasibility incorporating constraint within flight control system distributed electric propulsion by modifying commands for low-noise operation over sensitive areas, e.g., communities, schools, etc. Steady loading thickness signatures...

A spectral formulation is employed whereby in-plane stress waves are synthesized from the superposition of components at discrete frequencies and wavenumbers. The summations performed using fast Fourier transform series, respectively. Because discrete, solution to problems (over entire field) with completely arbitrary loading, both in time space, made tractable. Waves generated a line load acting on an infinite semiinfinite plane first considered. cascade approach then adopted for treatment...

This paper describes a new framework for the synthesis of aircraft flyover noise through nonstandard atmosphere. Central to is ray-tracing algorithm that defines multiple curved propagation paths, if atmosphere allows, between moving source and listener. Because each path has different emission angle, sound at must be performed independently path. The time delay, spreading loss, absorption (ground atmosphere) are integrated along applied synthesized simulate flyover. A final step assigns...

A new capability has been developed for the creation of virtual environments study aircraft community noise. It is applicable use with both recorded and synthesized When using noise, a three-stage process adopted involving non-real-time prediction synthesis stages followed by real-time rendering stage. Included in prediction-based source noise are temporal variations associated changes operational state, low frequency fluctuations that present under all operating conditions. stage effects...

The goal of this investigation is to further develop nonlinear modal numerical simulation methods for prediction geometrically response due combined thermalacoustic loadings.As with any such method, the accuracy solution dictated by selection basis, through which stiffness determined.In study, a suite available bases are considered including (i) bending modes only; (ii) coupled and companion modes; (iii) uncoupled (iv) membrane modes.Comparison these solutions in physical degrees-of-freedom...