Earphones and headphones, which are compact electro-acoustic transducers, tend to have a lot of acoustic absorption materials and porous materials known as dampers, which often have a large number of extremely small holes and narrow slits to inhibit the resonance of the vibrating system, because the air viscosity significantly affects the acoustic characteristics in such acoustic paths. In orde...

In this paper we describe a system which we have developed to measure cat ear canal specific acoustic impedance Zsp, magnitude and phase, as a function of frequency, for frequencies between 200 Hz and 33 kHz, and impedance magnitude between 4.0 to 4.0×105 [Rayles] (MKS). The object to be measured is placed at the end of a 3.5 mm diameter sound delivery tube. After a simple calibration procedure...

Transmission Loss (TL) of a glass cylinder tube containing a fluid is studied experimentally. This test specimen represents a typical double layer panel including a fluid. The tests are carried out by using a modified four-microphone standing-wave (impedance) tube for specimens with different lengths, 15 and 30 mm. Each cylinder tube is tested filled with one of the fluids at a time. The fluids...

The valveless impedance pump is a simple design that allows the producion or amplification of a flow without the requirement for valves or impellers. It is based on fluid-filled flexible tubing, connected to tubing of different impedances. Pumping is achieved by a periodic excitation at an off-centre position relative to the tube ends. This paper presents a comprehensive study of the fluid and ...

As a fundamental study on the electric method for measuring root canal length, the various factors which affect the measured impedance were investigated using a wide range of frequencies. 1) The impedance between two saliva ejectors in contact with the oral mucosa near the bilateral premolars in the lower arch generally showed low values. The difference between the maximum and minimum measured ...

A measurement system is described for acoustic absorption of automotive carpets and materials using the cepstrum technique. The system is based on prior work by Bolton [1] with modern software and hardware implementation. Time-domain averaging, minimumphase signal generation, late echo removal, and low-frequency data synthesis are implemented using commonly-available commercial hardware and sof...

Acoustic performance for an interior requires an accurate description of the boundary materials' surface acoustic impedance. Analytical methods may be applied to a small class of test geometries, but inverse numerical methods provide greater flexibility. The parameter estimation problem requires minimizing prediction vice observed acoustic field pressure. The Bayesian-network sampling approach ...