Schlieren flow visualizations of transverse oscillations of jets submitted to an acoustic perturbation are analyzed in this paper. The aim is to estimate the shape and the position of the median line of the jet. Two methods for image processing are proposed, based on complementary approaches : inter image and intra image analysis. Synthesized images of an oscillating jet are used to validate each method and compare their performances in the case of noisy pictures. Illustrations are then shown on real laminar and turbulent jets. The results obtained using both methods are very close, showing their reliability. Applications investigated in this paper are focused on the estimation of the convection velocity of perturbations along the jet, and the influence of the Reynolds number and of the channel geometry upstream the jet formation.

The sound produced by flutes depends not only on the physical characteristics of the instrument butalso on the control exerted by the musician. The latter is very important in some instruments of the flute family,especially in those where the air jet is shaped with the lip of the player.Some of the most relevant parameters controlled by the flautist, such as the distance from the lips to the sharp edge, the shape of the lips hole and the speed of the jet, are experimentally measured in this paper.Data produced by an experienced and anovice flautist are collected, analyzed and compared. Subjects are studied under normal musical playing conditions, playing phrases made out of simple musical intervals with subjective dynamics. Images of performer'sl ips are taken together with measurements of the blowing pressure and the sound radiated by the instrument. Data analysis shows remarkable differences between the twos ubjects. The optimized coordination of several parameters in order to obtain a desired musical response, coupling between performer'smouth and the instrument, as well as the efficient use of the available resources are some of the differences observed. PACS no. 43.75 740 ©S.Hirzel Verlag · EAA de la Cuadra et al.: Flute control parameters ACTA ACUSTICA UNITED WITH ACUSTICA Vol. 94 (2008)

Guidelines have been developed to improve the treatment of community-acquired pneumonia (CAP) but information regarding their influence on costs is lacking. The aim of the present study was to conduct a cost-effectiveness analysis of CAP treatment from the hospital perspective when adhering to Spanish guidelines.A prospective cohort study was performed in 271 patients with CAP admitted to a tertiary-care hospital, not needing intensive care. Collected data included patients' characteristics, comorbidity, initial risk class, resource use (medication, blood and microbiological analyses, and radiology) and economic data. Antimicrobial treatment was recorded as adherent or nonadherent to Spanish guidelines. Outcome measures were mortality and readmission at 30 days.The median cost for adherent treatment was 1,665.5 versus 1,710.5 Euros for nonadherent treatment. Mortality and readmission were 10% and 2.1% for adherent treatment versus 13.6% and 6.2% for nonadherent treatment. The cost-effectiveness ratio was 2,277 Euros per expected cure for patients treated according to the guidelines and 2,567 Euros per expected cure for the nonadherence group. The incremental cost-effectiveness ratio showed that adherence to treatment guidelines saved 1,121 Euros per patient cured compared with nonadherence. The sensitivity analysis demonstrated that the findings were robust.An antimicrobial treatment according to guidelines is the dominant alternative due to its costeffectiveness.

Self-sustained musical instruments are complex nonlinear dynamical systems which are known to produce a wealth of dynamical regimes. This includes different kinds of non periodic sounds, which are either played on purpose or avoided depending on the cultural and musical context. We investigate non-periodic sounds produced by two types of flute-like instruments, namely an alto recorder and traditional pan-like flutes from Central Chile. We adopt a nonlinear dynamics point of view to characterize the multiphonics produced by the alto recorder and the sonidos rajados produced by the Chilean flutes. Our results unveil the common quasiperiodic nature of the two types of sound regimes, and suggest that they result from a similar physical sound production mechanism. This paves the way for a better control of non periodic sound regimes by the instrument makers.

A simple analytical model for the interaction between a plane jet issued from a flue and a transverse acoustic disturbance is developed in this paper. The model is inspired by direct flow simulation results confronted to experimental data. The interaction is expected to take place in the vicinity of the separation points of the jet. The influence of the detailed geometry of the channel end on the jet receptivity is discussed, and more specifically the chamfer geometries found in flute-like musical instruments. The simplified model explains quite well the difference between the jet response of a flue with square edges compared to a chamfered flue exit. The effect of rounded, lip-like flue exit is not well captured by the model.