Saman Farhangdoust, I. A. Adediran, M. Ranjbar
et al.
This research develops lightweight stepped cantilever beams using two auxetic hexagonal and anti-tetrachiral designs to reduce sound radiation from vibrating modes of attached structures. A finite element analysis (FEA) is employed to investigate the equivalent radiated power level (ERPL) of the proposed beams subjected to different excitations. A computational parametric study is performed to minimize the ERPL for two in-plane and out-of-plane configurations of the beams over a frequency range of 0 Hz to 1200 Hz. The vibro-acoustic responses of the beams are validated by two acoustic techniques of the radiated sound pressure level (RSPL) and far-field sound pressure level (FFSPL). Numerical results demonstrate an excellent vibro-acoustic performance in reducing the radiated sound power level for the beams. The proposed beams can be utilized for high-tech devices where the radiated noise control is desired. This paper opens up a great potential of using auxetic stepped cantilever beams for various engineering applications in Acoustics, Civil, Aerospace, Biomedical, and Mechanical Engineering.
Acoustic metamaterials (AMM) have become a very active topic for research in numerous domains of engineering and science because of their promise to create materials, structures, and devices that can control acoustic wave propagation in ways that exceed the capabilities of naturally occurring or conventional composite materials. The majority of AMM research has been focused on linear behavior such as negative dynamic effective stiffness and density, cloaking, and negative refraction. One drawback of the focus on linear behavior is the restriction of the effective material properties of interest to narrow frequency bands that cannot be changed with external stimulus. Nonlinearity has been explored as a means of increasing the bandwidth of performance by enabling tunable band gaps and material configurability. Other recent work has investigated nonlinear AMM to access phenomena such as harmonic generation, non-reciprocity, enhanced energy absorption, solitons, mode hopping and conversion, chaos, and intrinsic localized modes. This talk will provide an overview of nonlinear AMM, starting with a background on AMM, then surveying existing research on the topic and its relationship to seminal works in nonlinear acoustics, and finally discussing promising avenues of future research. [Work supported by the National Science Foundation EFRI program and ARL:UT.]
Broad implementation of normal-incidence echo sounding has generated a need for sediment characterization models. These models may utilize the magnitude, phase, and/or envelope shape of reflected acoustic waveforms to infer physical, geoacoustic, and engineering properties of ocean sediment. Normal-incidence echo soundings enable the remote survey of vast underwater areas at a fraction of the cost of ground truth sampling methods, i.e., cores and grabs. In collaboration with the Dauphin Island Sea Lab, acoustic data was collected in the Petit Bois Pass off of the Alabama coast. The magnitude, pulse width, and skew ratio of the matched filter output were measured and quantified as bottom loss, full-width at half-max, and the ratio of half-width at half-max, respectively. Bottom loss measurements were used to determine the index of impedance which, through the application of empirically based regression equations, was then used to calculate sound speed ratio, density, mean grain size, and porosity of the sediment along the survey track. The estimated values of sediment properties are generally in agreement with those measured in the laboratory by ground truth survey. [Work supported by the Office of Naval Research, Ocean Acoustics.]Broad implementation of normal-incidence echo sounding has generated a need for sediment characterization models. These models may utilize the magnitude, phase, and/or envelope shape of reflected acoustic waveforms to infer physical, geoacoustic, and engineering properties of ocean sediment. Normal-incidence echo soundings enable the remote survey of vast underwater areas at a fraction of the cost of ground truth sampling methods, i.e., cores and grabs. In collaboration with the Dauphin Island Sea Lab, acoustic data was collected in the Petit Bois Pass off of the Alabama coast. The magnitude, pulse width, and skew ratio of the matched filter output were measured and quantified as bottom loss, full-width at half-max, and the ratio of half-width at half-max, respectively. Bottom loss measurements were used to determine the index of impedance which, through the application of empirically based regression equations, was then used to calculate sound speed ratio, density, mean grain size, and porosity of the se...
Inhalers are devices which deliver medication to the airways in the treatment of chronic respiratory diseases. When used correctly inhalers relieve and improve patients' symptoms. However, adherence to inhaler medication has been demonstrated to be poor, leading to reduced clinical outcomes, wasted medication, and higher healthcare costs. There is a clinical need for a system that can accurately monitor inhaler adherence as currently no method exists to evaluate how patients use their inhalers between clinic visits. This paper presents a method of automatically evaluating inhaler adherence through acoustic analysis of inhaler sounds. An acoustic monitoring device was employed to record the sounds patients produce while using a Diskus dry powder inhaler, in addition to the time and date patients use the inhaler. An algorithm was designed and developed to automatically detect inhaler events from the audio signals and provide feedback regarding patient adherence. The algorithm was evaluated on 407 audio files obtained from 12 community dwelling asthmatic patients. Results of the automatic classification were compared against two expert human raters. For patient data for whom the human raters Cohen's kappa agreement score was , results indicated that the algorithm's accuracy was 83% in determining the correct inhaler technique score compared with the raters. This paper has several clinical implications as it demonstrates the feasibility of using acoustics to objectively monitor patient inhaler adherence and provide real-time personalized medical care for a chronic respiratory illness.