Flow disturbances are generated inside a duct via pulsed injection of helium into a flow of air. This leads to the generation of an acoustic pulse (direct noise), as well as the production of entropic and compositional inhomogeneities which are convected with the mean flow. As these inhomogeneities are convected through a choked nozzle, they generate indirect noise. The resulting acoustic press...

Generally, the sound signal produced by transmission unit or cutting unit contains abundant information about the working state of a machine. The acoustic-based diagnosis system presents some distinct advantages in some severe conditions particularly due to its unique non-contact measurement and unlimited use at the installation site. However, the original acoustic signal collected from manufac...

The interference algorithm of the acoustic tomography of' the ocea.n i s discussed, In this method the synoptic inhomogeneities of the sound velocity field are restored by the perturbations in the intermode phase Merences. The hiermoile phase difference, in its turn, is determined by the measured space distribution of the intensity (the interference structure) of the acoustic field. The interfe...

PhotoAcoustic Tomography (PAT) uses light to create sound sources (by heat generated on optical absorption) and image reconstruction consists of an inverse acoustic source reconstruction, which can be done using conventional ultrasound methods. In order to quantify the optical properties underlying the sound generation it is necessary to couple models for optical and acoustic propagation. In th...

Photoacoustic tomography (PAT) is new imaging modality for visualizing the optical absorption coefficient of a probe. It has proven great promise for a variety of biomedical applications, such as imaging of animals, early cancer diagnostics, and imaging of vasculature (see [9, 21, 27, 30, 38, 39, 40, 43]). PAT is based on the excitation of acoustic pressure waves by illuminating a probe with sh...

The acoustic properties of aqueous solutions of dextran are characterized in the frequency range of 70-400 MHz by the bio-ultrasonic spectroscopy system using an ultrasonic transmission comparison method. The attenuation, velocity, impedance, and density of aqueous dextran solutions, for six molecular weights in the range of 10,400-2,000,000 Da in the concentration range 520% by weight, are rep...

In recent years, underwater acoustic wireless sensor networks have been used in many areas. There have been many field trials of acoustic propagation models and statistics for shallow water conditions. However, field trials are limited environmentally and, hence, not widely accepted. Simulations of the impulse response of a shallow underwater acoustic channel allows less expensive system tests ...

PURPOSE To determine whether unenhanced high-resolution T2-weighted fast spin-echo MR imaging provides an acceptable and less expensive alternative to contrast-enhanced conventional T1-weighted spin-echo MR techniques in the diagnosis of acoustic schwannoma. METHODS We reviewed in a blinded fashion the records of 25 patients with pathologically documented acoustic schwannoma and of 25 control...

Attenuation estimation and imaging in the cervix has been utilized to evaluate the onset of cervical ripening during pregnancy. This feature has also been utilized for the acoustic characterization of leiomyomas and myometrial tissue. In this paper, we present direct narrowband substitution measurement values of the variation in the ultrasonic attenuation coefficient in ex vivo human uterine an...