Since the installation of an ITER-like wall, the JET programme has focused on the consolidation of ITER design choices and the preparation for ITER operation, with a specific emphasis given to the bulk tungsten melt experiment, which has been crucial for the final decision on the material choice for the day-one tungsten divertor in ITER. Integrated scenarios have been progressed with the re-establishment of long-pulse, high-confinement H-modes by optimizing the magnetic configuration and the use of ICRH to avoid tungsten impurity accumulation. Stationary discharges with detached divertor conditions and small edge localized modes have been demonstrated by nitrogen seeding. The differences in confinement and pedestal behaviour before and after the ITER-like wall installation have been better characterized towards the development of high fusion yield scenarios in DT. Post-mortem analyses of the plasma-facing components have confirmed the previously reported low fuel retention obtained by gas balance and shown that the pattern of deposition within the divertor has changed significantly with respect to the JET carbon wall campaigns due to the absence of thermally activated chemical erosion of beryllium in contrast to carbon. Transport to remote areas is almost absent and two orders of magnitude less material is found in the divertor.

Noise measurements near the F-35A Joint Strike Fighter at military power are analyzed via spatial maps of overall and band pressure levels and skewness. Relative constancy of the pressure waveform skewness reveals that waveform asymmetry, characteristic of supersonic jets, is a source phenomenon originating farther upstream than the maximum overall level. Conversely, growth of the skewness of the time derivative with distance indicates that acoustic shocks largely form through the course of near-field propagation and are not generated explicitly by a source mechanism. These results potentially counter previous arguments that jet “crackle” is a source phenomenon.

Accurate measurement of the noise fields emitted by a full scale high performance jet engine and jet plume (with supersonic jet flow) requires detailed planning and careful execution. The apparent acoustic source can be very large, more than 50 feet long and 20 feet high and wide. The jet plume contains many noise generating sources, the main two being shock (broad band and shock cells) and turbulent mixing. This paper is an initial description of a detailed method to accurately measure and describe the near-field noise while simultaneously measuring the far-field noise. For a large high performance jet engine, the acoustic far-field may not be formed until more than 1000 ft away from the plume. The paper also describes proposed methods to measure the non-linear propagation of the noise from the near-field to the far-field. The proposed methodology described with vetting will be considered as an US military standard (MILSTD) with possible later consideration as American standard measurement technique to describe noise fields for personnel noise exposure and for measuring the performance of jet engine noise reduction technologies.

This study examined the effect of multiple presentations on signal detection and on signal recognition (identifying one signal from a set of four possible signals) for three different sets of signals. One set was four sinusoids (100-ms duration, frequencies of 707, 1000, 1414, and 2000 Hz). Two sets contained tonal patterns each made of a sequence of seven, 100-ms, sinusoidal components. In the first set, the four patterns consisted of the same seven sinusoids in different orders. In the second set, the four patterns had the same order of relative frequencies, but had frequencies from different 1/4 oct bands centered at 707, 1000, 1414, and 2000 Hz. All stimuli were adjusted to be equally detectable in the presence of a continuous white noise (eta 0 = 20 dB SPL). Each trial contained 1, 2, 4, 8, or 16 presentations of a given signal plus noise (probability of a signal was 0.5) or noise alone. Detectability of the sinusoids generally increased as the square root of the number of presentations; detectability for the tonal patterns increased at a slower rate. Recognition was generally poorer than predicted by the recognition theorem [S.J. Starr, C. E. Metz, L.B. Lusted, and D.J. Goodenough, Radiology 116, 533-538 (1975)] and increased with multiple presentations only as much as expected from the increase in signal detectability.

Aircraft noise has been traditionally measured with either a few ground-based microphones or a linear ground-plane array of microphones. These techniques capture one-dimensional and/or two-dimensional characteristics of aircraft flight noise. The US Air Force Research Laboratory has started the construction of a 3-dimensional measurement facility at White Sands Missile Range in New Mexico. This facility, the Aeroacoustic Research Complex (ARC), will allow aircraft to fly through the array, collecting fully 3D acoustic data. ARC is initially being developed in two phases The first phase includes two 91.4 m tall towers separated by 244 m and will focus on noise from rotary wing and UAV aircraft. The second phase will add two 366 m tall towers separated by 610 m and will focus on large and high performance fixed wing aircraft. This facility will allow more accurate characterization of in-flight noise directivity by providing synchronized 3-dimensional magnitude & spectral acoustical signatures from 50+ microphones. ARC responds to a critical need for validation of existing predictive acoustic models. Such models are used for aircraft design, survivability, nonlinear acoustic propagation research and assessing noise exposure to residents living adjacent to airfields.