A previous study [J. Acoust. Soc. Am. 111, 1102-1109 (2002)] showed that the occurrence of ultrasonically induced lung hemorrhage in rats was directly correlated to the level of lung inflation. In that study, it was hypothesized that the lung could be modeled as two components consisting of air and parenchyma (contiguous tissue [pleura and septa]). The speed of sound and lung impedance would th...

The normal sound absorption coefficients of two different test objects in an impedance tube are measured with two different methods: The standing wave ratio method (ISO 10534-1:1996) and the transfer function method (ISO 10534-2:1998). From the latter is the specific acoustic impedance ratio calculated. The test objects are two cellular plastics: AC 30 S and FIRE 30 VF (both are 30 mm thick), t...

Standing waves, resonances and/or singularities during measurement and calibration often limit the precision of measurements of acoustic reflection spectra and acoustic impedance spectra. This paper reviews and compares several established techniques, and then describes techniques that incorporate some or all of three features that together considerably improve precision and signal:noise ratio....

Quantifying how the sound delivered to the ear canal relates to hearing threshold has historically relied on acoustic calibration in physical assemblies with an input impedance intended to match the human ear (e.g., a Zwislocki coupler). The variation in the input impedance of the human ear makes such a method of calibration questionable. It is preferable to calibrate the acoustic signal in eac...

The use of porosity to modify the functional properties of piezoelectric ceramics is well known in the scientific literature as well as by the industry, and porous ceramic can be seen as a 2-phase composite. In the present work, examples are given of applications where controlled porosity is exploited in order to optimise the dielectric, piezoelectric and acoustic properties of the piezoceramic...

The acoustic coupling between the voice production system and the vocal tract has a significant influence on the production of voice. In this study, the coupling effect was represented using the acoustic pressure difference across the glottis, which is capable of inducing a flow, and the mean acoustic pressure in the glottis, which acts as a driving force for the vocal folds. These specific aco...

INTRODUCTION Controversies arise with respect to functioning of the middle ear over time. OBJECTIVE To assess changes in middle ear impedance that may be related to aging, and/or if there was an association of these changes with those of the inner ear in the elderly patients. METHODS Cross-sectional, comparative study of elderly patients managed in ear, nose and throat clinics. A structured...

This paper will provide an overview of a patented acoustic technique known as Acoustek ® that has been developed to detect features, such as blockages and leakages in gas pipelines. The technique involves injecting an acoustic, or pressure pulse into the gas within the pipeline. This acoustic pulse will travel as a plane wave along the pipeline and will be partially reflected wherever there is ...

Acoustic measurements provide convenient non-invasive means for the characterisation of materials. We show here for the first time how a commercial impedance tube can be used to provide accurate measurements of the velocity and attenuation of acoustic waves in liquid foams, as well as their effective "acoustic" density, over the 0.5-6kHz frequency range. We demonstrate this using two types of l...

Polypropylene films exhibit strong mechanical properties, low acoustic impedance, and sensitivity to slip shear pressure, making them excellent electromechanical sensors.