Low-frequency active noise control of an underwater large-scale structure with distributed giant magnetostrictive actuators

A light and thin underwater large-plate active acoustic structure is developed that satisfies the particular requirements of high pressure resilience, low frequency and high efficiency encountered in underwater work environments. A low-frequency miniaturized active control unit, with a thickness of less than 50 mm, is designed using giant magnetostrictive material (GMM). The noise reduction performance is measured with an active control system based on a multi-channel adaptive filter. The active control system is developed within a LabVIEW environment and can achieve significant levels of noise reduction within time intervals of less than one second achieving absorption coefficients far exceeding 0.8 even under high pressures. The new active-control system incorporates hardware and software components and represents a novel technology for low-frequency underwater noise reduction

Actuator Feasibility Study for Active Control of Ducted Axial Fan Noise

A feasibility study was performed to investigate actuator technology which is relevant for a particular application of active noise control for gas turbine stator vanes. This study investigated many different classes of actuators and ranked them on the order of applicability. The most difficult requirements the actuators had to meet were high frequency response, large amplitude deflections, and a thin profile. Based on this assessment, piezoelectric type actuators were selected as the most appropriate actuator class. Specifically, Rainbows (a new class of high performance piezoelectric actuators), and unimorphs (a ceramic/metal composite) appeared best suited to the requirements. A benchtop experimental study was conducted. The performance of a variety of different actuators was examined, including high polymer films, flextensional actuators, miniature speakers, unimorphs, and Rainbows. The displacement/frequency response and phase characteristics of the actuators were measured. Physical limitations of actuator operation were also examined. This report includes the first known, high displacement, dynamic data obtained for Rainbow actuators. A new "hard" ceramic Rainbow actuator which does not appear to be limited in operation by self heating as "soft" ceramic Rainbows was designed, constructed and tested. The study concludes that a suitable actuator for active noise control in gas turbine engines can be achieved with state of the art materials and processing

A state-of-the-art assessment of active structures

A state-of-the-art assessment of active structures with emphasis towards the applications in aeronautics and space is presented. It is felt that since this technology area is growing at such a rapid pace in many different disciplines, it is not feasible to cover all of the current research but only the relevant work as relates to aeronautics and space. Research in smart actuation materials, smart sensors, and control of smart/intelligent structures is covered. In smart actuation materials, piezoelectric, magnetostrictive, shape memory, electrorheological, and electrostrictive materials are covered. For sensory materials, fiber optics, dielectric loss, and piezoelectric sensors are examined. Applications of embedded sensors and smart sensors are discussed

Electrophysiologic assessment of (central) auditory processing disorder in children with non-syndromic cleft lip and/or palate

Session 5aPP - Psychological and Physiological Acoustics: Auditory Function, Mechanisms, and Models (Poster Session)Cleft of the lip and/or palate is a common congenital craniofacial malformation worldwide, particularly non-syndromic cleft lip and/or palate (NSCL/P). Though middle ear deficits in this population have been universally noted in numerous studies, other auditory problems including inner ear deficits or cortical dysfunction are rarely reported. A higher prevalence of educational problems has been noted in children with NSCL/P compared to craniofacially normal children. These high level cognitive difficulties cannot be entirely attributed to peripheral hearing loss. Recently it has been suggested that children with NSCLP may be more prone to abnormalities in the auditory cortex. The aim of the present study was to investigate whether school age children with (NSCL/P) have a higher prevalence of indications of (central) auditory processing disorder [(C)APD] compared to normal age matched controls when assessed using auditory event-related potential (ERP) techniques. School children (6 to 15 years) with NSCL/P and normal controls with matched age and gender were recruited. Auditory ERP recordings included auditory brainstem response and late event-related potentials, including the P1-N1-P2 complex and P300 waveforms. Initial findings from the present study are presented and their implications for further research in this area —and clinical intervention—are outlined. © 2012 Acoustical Society of Americapublished_or_final_versio