Comparison of high-intensity sound and mechanical vibration for cleaning porous titanium cylinders fabricated using selective laser melting

Orthopedic components, such as the acetabular cup in total hip joint replacement, can be fabricated using porous metals, such as titanium, and a number of processes, such as selective laser melting. The issue of how to effectively remove loose powder from the pores (residual powder) of such components has not been addressed in the literature. In this work, we investigated the feasibility of two processes, acoustic cleaning using high‐intensity sound inside acoustic horns and mechanical vibration, to remove residual titanium powder from selective laser melting‐fabricated cylinders. With acoustic cleaning, the amount of residual powder removed was not influenced by either the fundamental frequency of the horn used (75 vs. 230 Hz) or, for a given horn, the number of soundings (between 1 and 20). With mechanical vibration, the amount of residual powder removed was not influenced by the application time (10 vs. 20 s). Acoustic cleaning was found to be more reliable and effective in removal of residual powder than cleaning with mechanical vibration. It is concluded that acoustic cleaning using high‐intensity sound has significant potential for use in the final preparation stages of porous metal orthopedic components. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 117–123, 2017

Reciprocal auditory attenuation affects looking behaviour and playing level but not ensemble synchrony: A psychoacoustical study of violin duos

Evidence suggests that musicians may be more susceptible to developing a hearing impairment due to increased exposure to loud sounds over the lifespan. Hearing impairments can affect musical performance behaviours, yet research suggests they do not significantly affect ensemble synchrony unless the hearing loss is severe or profound. This study investigated the effect of reduced auditory feedback on ensemble synchrony, looking behaviour and playing level. Four violinists, with self-reported normal hearing, formed two duos in acoustically-isolated rooms separated by a glass window. Each player received feedback from their own and their co-performer’s playing attenuated by 0, 10, 20, 30 and 40 dB. Video recordings of their looking behaviours were coded and signed asynchronies were identified in the audio files. The strongest effects found were bi-directional changes to playing levels as a result of auditory feedback levels, which increased when a player’s own feedback was reduced and reduced when co-performer feedback was attenuated. Violinists’ looking behaviour was found to increase when co-performer feedback was attenuated by 20 dB or more relative to their own, such that they glanced more frequently and looked for longer towards their partners. There were no effects of auditory attenuation on ensemble synchrony, even with 40 dB attenuation. The results indicate that “self-to-other” sound level ratios are more likely to prompt compensatory musical performance behaviours than an individual’s hearing ability

The Primordial Inflation Explorer (PIXIE) Mission

The Primordial Inflation Explorer (PIXIE) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from frequencies 30 GHz to 6 THz (I cm to 50 I-tm wavelength). PIXIE uses a polarizing Michelson interferometer with 2.7 K optics to measure the difference spectrum between two orthogonal linear polarizations from two co-aligned beams. Either input can view either the sky or a temperature-controlled absolute reference blackbody calibrator. The multimoded optics and high etendu provide sensitivity comparable to kilo-pixel focal plane arrays, but with greatly expanded frequency coverage while using only 4 detectors total. PIXIE builds on the highly successful COBEIFIRAS design by adding large-area polarization-sensitive detectors whose fully symmetric optics are maintained in thermal equilibrium with the CMB. The highly symmetric nulled design provides redundant rejection of major sources of systematic uncertainty. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much less than 10(exp -3). PIXIE will also return a rich data set constraining physical processes ranging from Big Bang cosmology, reionization, and large-scale structure to the local interstellar medium. Keywords: cosmic microwave background, polarization, FTS, bolomete

The interaction of sound with powdered material

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Prediction of Maximum Fast Time-Weighted Sound Pressure Levels from Time-Varying Structure-Borne Sound Sources in Heavyweight Buildings

At present the prediction model in EN 12354-5 for sound transmission due to structure-borne excitation from building machinery is limited to sources running under steady-state conditions. As machinery noise also needs to be assessed under time-varying conditions, building regulations on installation noise in some European countries set requirements based on the maximum Fast time-weighted sound pressure level in the receiving room. This paper proposes an approach that could predict this information at the design stage and validates it using idealised time-varying signals applied via a shaker into a concrete floor. A heavyweight reception plate is used to quantify the structure-borne sound power using equivalent continuous levels over 125ms time periods from which the highest value can be used as the power input into an SEA or SEA-based prediction model. An empirical correction (developed in previous work by the authors) is then applied to the output from this model to estimate the maximum Fast time-weighted sound pressure level. This approach is validated with measurements in a room below a concrete floor (where there is suppressed flanking transmission) from which the results show close agreement between predictions and measurements for one-third octave bands and A-weighted values