[Show abstract][Hide abstract] ABSTRACT: A video measuring installation for registering low-frequency acoustic vibrations in two orthogonal directions with conversion of the results into a WAV-format file is described. The capabilities of the system in the detection of test mechanical vibrations at a frequency of 300 Hz were experimentally studied. The resolution of the system is 3 μm, and its dynamic range is 23 dB. The installation can be used in studies of vibrations of engineering and natural objects.
[Show abstract][Hide abstract] ABSTRACT: The objective of this work is to simulate the flow noise of a vector sensor embedded in a flexible towed array. The mathematical model developed, based on long-wavelength analysis of the inner space of a cylindrical multipole source, predicts the reduction of the flow noise of a vector sensor embedded in an underwater flexible towed array by means of intensimetric processing (cross-spectral density calculation of oscillatory velocity and sound-pressure-sensor responses). It is found experimentally that intensimetric processing results in flow noise reduction by 12-25 dB at mean levels and by 10-30 dB in fluctuations compared to a squared oscillatory velocity channel. The effect of flow noise suppression in the intensimetry channel relative to a squared sound pressure channel is observed, but only for frequencies above the threshold. These suppression values are 10-15 dB at mean noise levels and 3-6 dB in fluctuations. At towing velocities of 1.5-3 ms(-1) and an accumulation time of 98.3 s, the threshold frequency in fluctuations is between 30 and 45 Hz.
The Journal of the Acoustical Society of America 05/2012; 131(5):3755-62. DOI:10.1121/1.3693647 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Diving renders negative influence on human respiratory system especially when oxygen breathing apparatus aimed for military divers is used. Spirometry indexes have poor sensitivity to toxic effect of hyperbaric hyperoxia. Objective is to develop new acoustic instrumentation for revealing minimum impairments of lung function in oxygen divers. The apparatus has been designed which is based on analysis of forced expiratory tracheal noise duration (FETND). This apparatus contains acoustic sensor, input device, portable personal computer and specially designed software. 48 divers before and after single shallow water dive in oxygen closed-type breathing apparatus were tested by means of this acoustic tool. After dive a significant drop of spirometric indexes forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1) over the group as a whole was found. The significant increase of individual FETND, exceeding the natural variability limit, was found in 10 subjects (20.8%). Three of them during dive had respiratory symptoms characteristic for initial manifestations of pulmonary oxygen poisoning. Two of them had essential drop of FEV1. The asymptomatic reversible increase of FETND in the rest 7 divers was interpreted as a sign of obstructive impairments caused by hidden phase of hyperbaric hyperoxia effect. Thus developed acoustic tool is useful to monitor ventilation function of lungs in military/civil divers and other persons working in harmful gas media such as firefighters, astronauts and so on.
[Show abstract][Hide abstract] ABSTRACT: We develop a laboratory setup to estimate the force of rotation of a metal branch pipe in a viscoelastic medium. We show that
2-min action of shearing ultrasonic oscillations (frequency, 32.5 kHz; specific power, no more than 0.008 W/cm2) reduces by 17% the static limit of fluidity brought to an initial temperature of Ì-100 fuel oil cooled to −15°C in the wall
layer of a rotating branch pipe. We obtain a linear regression dependence between the ratio of the threshold force of the
onset of branch pipe motion to the consumption current of the ultrasonic transducer and the fuel temperature.
[Show abstract][Hide abstract] ABSTRACT: Lumen probing of human lungs with complex acoustic signals in the frequency band from 100 to 1000 Hz made it possible for
the first time to explicitly confirm the concurrent existence of two mechanisms differing in propagation velocity behind the
transmission of acoustic vibrations from the oral cavity to the thoracic cage surface. The numerical values of propagation
time lags allowed one of these mechanisms to be associated with combined aerial-structural transmission and the other, with
purely structural transmission.
[Show abstract][Hide abstract] ABSTRACT: Laboratory installation for acoustic sounding of human lungs by complex signals has been developed. Linear frequency sweep
signal (80-1000 Hz, 20 s) and the signal containing m-coded (the basis - 511 readouts) phase-manipulated fragments with three
various carrying frequencies (200, 300, 750 Hz) are entered into mouth. Pilot experiment has been carried out with 3 volunteers.
Results of processing of sounding signals received on the chest surface by convolution method show, that the pictures of arrivals
of sounding signal are various above the top, middle and basal areas of lungs, and have steady (replicating from attempt to
attempt and from one kind of signals to another) specific features connected with time delays of arrivals, ratio of amplitudes
of maxima of arrivals. In basal areas of lungs two various arrivals of both sounding signals have been directly found. This
testifies to existence, at least, two various ways of sound transmission in human lungs, distinguished on resulting sound
velocity of mechanical oscillations. Subject’s individuality, dependent on body build and age related condition of lung parenchyma,
was found both in time delays between emission of sounding signal and reception of the first arrival, and time delays between
the first and the second arrivals. The developed method seems to be promising for non ionizing transmission low frequency
acoustic tomography of lungs.
[Show abstract][Hide abstract] ABSTRACT: Within the framework of a specified acousto-biomechanical model, a possibility of explaining wheezes during forced expiration on the basis of a vortex separation mechanism is tested and the localization of the zones in the bronchial tree where forced expiratory wheezes are generated is refined. As an experimental model, a group of 18 healthy volunteers from 18 to 44 years old (median is equal 19) was used. On the basis of linear regression modeling the relationship between the principal spectral frequency of medium-frequency forced expiratory wheezes (400–600 Hz) recorded on the trachea and the standard volume flow-rates of expired air measured in computer spirometry is analyzed. The data obtained show that vortex separation in the air flow at the bronchial tree bifurcations (where a stepwise increase in the cross-section area takes place) is a probable mechanism of medium-frequency forced expiratory wheeze generation and that during the forced expiratory maneuver the vortex separation zone tends to be displaced deeper into the bronchial tree.
[Show abstract][Hide abstract] ABSTRACT: The authors developed a method for more precise detection and analysis of the physical features of respiratory and voice sound transmission to the chest wall. Based on their findings using this method, they designed several devices for acoustic examination and evaluation of components of human respiratory sounds. These devices analyze forced expiratory sounds, distinguish between air-borne and structure-borne sounds, and distinguish abnormalities in voice transmission to the chest wall. Tests of the devices on human subjects confirmed the validity of the authors' theoretical models, which offer promise for the development of a new class of medical diagnostic instruments.