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The goal of this experimental research is to determine the potential of pure acoustic detection for hostile fire indication for helicopters, while guarantying a very low true false alarm rate in the case of high helicopter speed, large helicopter bullet distance range and small calibres. An integration into a multi-sensor system, could provide a fully embedded, defence-feature technology capable of immediately alerting a helicopter crew that even a small projectile has closely passed by their machine, and provide an indication of the bullet trajectory. This article summarizes the design, the test in real-flight situation, and the performance results of an experimental acoustic array demonstrator developed for this purpose and evaluated for a referential of situations of 4 small arms firings with calibres from 5.56 mm to 12.7 mm and a total of 592 firings  52 flight exposure situations (altitude, hover, speed, orientation). The detection system is an experimental planar, centimetric, acoustic array recording unit designed for low sensitivity to laminar and turbulent air flow, rear pressure and vibrations and high acoustic selectivity. This is combined with a transient signal post-processing solver that is implemented as a deterministic cost minimization function. The conclusion of the research is a strong confirmation of the feasibility of an under-helicopter acoustic detection of small calibres hostile firings as well as the proposal of a general performance law for the capability of such a system to detect small calibres, including passing-by distances of up to several hundreds of m and speeds of up to 120 kn.

A current concern of armasuisse is the feasibility of a fixed or mobile acoustic surveillance and recognition network of sensors allowing to permanently monitor the noise immissions of a wide range of aerial activities such as civil or military aviation, and other possible acoustic events such as transient events, subsonic or sonic booms or other. This objective requires an ability to detect, localize and recognize a wide range of potential acoustic events of interest, among others possibly parasitic acoustic events (natural and industrial events on the ground for example), and possibly high background noise (for example close to urban or high activity areas). This article presents a general discussion and conclusion about this problem, based on 20 years of experience totalizing a dozen of research programs or internal researches by IAV, with an illustration through one central specific experimental case-study carried out within the framework of an armasuisse research program.

Objectives This study was undertaken to assess concurrent mechanical stresses from shock, vibration, and noise to which a critically ill neonate is exposed during emergency transfer. Methods For neonates transported by a French specialized emergency medical service, we measured and analyzed 27 physical parameters recorded during typical transport by ambulance and by helicopter. The noninvasive sensors were placed to allow better representation of the exposure of the newborn to the physical constraints. Results Based on 10 hours of transport by ambulance and 2 hours by helicopter, noise, whole body vibration, rate of turn, acceleration, and pitch were extracted as the five most representative dynamic harshness indicators. A helicopter produces a higher-level but more stable (lower relative dispersion) whole body dynamic exposure than an ambulance, with a mean noise level of 86 ± 1 dBA versus 67 ± 3 dBA, mean whole body vibration of 1 ± 0.1 meter per second squared (m/s 2 ) versus 0.4 6 0.2 m/s 2 , and acceleration of 1 6 0.05 m/s 2 versus 0.4 6 0.1 m/s 2 . A ground ambulance has many more dynamic effects in terms of braking, shock, and impulsive noise than a helicopter (1 impulsive event per 2 minutes vs. 1 per 11 minutes). Conclusions Our results show significant exposure of the sick neonate to both stationary and impulsive dynamic physical stressors during transportation, particularly in a ground ambulance. The study suggests opportunities to reduce physical stressors during neonatal transport.

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The first recordings of acoustic signals associated with avalanches go back to the 1970s when premonitory low-frequency acoustic emission was observed in the snow cover just before the setting off of natural avalanches (Sommerfeld, 1977; Sommerfeld and Gubler, 1983). Recently, it has been demonstrated that avalanches also produce strong infrasonic vibrations in air during their movement. These infrasonic vibrations propagate great distances and can follow the natural relief. It was then a question of automatically detecting this emission to monitor avalanche activity, with a view to improving forecasting and assisting in the study of certain aspects of avalanche dynamics.With the double aim of pursuing investigations on the mechanics of the acoustic emission from avalanches and designing an automatic detection system, our laboratory has developed specific instrumentation, the essential link of which is an array of infrasonic microphones associated with a goniometer. Systematic measurements of the infrasonic emissions are being carried out, not only of the natural or released avalanches themselves but of all events with the aim of characterizing the former in relation to “infrasonic noise”.

The Laboratoire d’Electronique Industrielle has realized an active noise controller. The system is designed to efficiently attenuate low frequency transformer noise where passive methods are either ineffective or tend to be very expensive. This paper describes an acoustic mapping experiment: two loudspeakers simulate a transformer, the noise is measured by a 15 microphones antenna and the DSP calculates an acoustic map with the beamforming method. Simulation and experimental results are presented.

1447 Heart Rate Variability Analysis is of Limited Value in Assessing Stress Responsiveness During Neonatal Transport

OBJECTIVE: Nasal continuous positive airway pressure (nCPAP) has been shown to improve the outcome of infants with respiratory distress syndrome. However, noise generation could be of concern. Therefore, our study was designed to measure the noise levels of various CPAP drivers. DESIGN: For infants admitted to our neonatal intensive care unit and paediatric critical care unit, we measured the noise level in the oral cavity, using a microphonic probe with a flexible capillary tube. Various CPAP drivers and interfaces have been tested. RESULTS: 27 measurements were made in eight infants. Mean noise level was 88.6 (SD 18.8) dB and was correlated with flow (p