Experiments to investigate the acoustic properties of sound propagation

2018 ◽  
Vol 53 (4) ◽  
pp. 045007
Author(s):  
Omur E Dagdeviren
Keyword(s):  
Sound Propagation ◽  
Acoustic Properties

Cavity Resonance Biomedical Sensor

2014 ◽  
Author(s):  
Ralf Lucklum ◽  
Mikhail Zubtsov ◽  
Simon Villa Arango
Keyword(s):  
Chemical Sensor ◽  
Sound Propagation ◽  
Point Of Care ◽  
Phononic Crystal ◽  
Acoustic Properties ◽  
Cavity Resonance ◽  
Solid Matrix ◽  
Acoustic Coupling ◽  
Biomedical Sensors ◽  
Mems Resonator

We report on first steps towards a phononic crystal sensor for biomedical applications. Phononic crystals and metamaterials allow for unprecedented control of sound propagation. The classical ultrasonic sensors, acoustic microsensors and MEMS resonator sensors face severe limitations when applying them to small volume liquid analytes. Phononic crystal sensors are a new concept following the route of photonic crystal sensors. Basically, the material of interest, here a liquid analyte confined in a cavity of a phononic crystal having a solid matrix constitutes one component of the phononic crystal. In an application as chemical sensor the value of interest, let’s say the concentration of a toxic compound in liquid, is related to acoustic properties of the liquid in the cavity. A change in the concentration causes measurable changes in the properties of the phononic crystal. Transmission or reflection coefficients are appropriate parameters for measurement. Specifically, a resonance induced well separated transmission peak within the band gap is the most favorable feature. The sensor scheme therefore relies on the determination of the frequency of maximum transmission as measure of concentration. Promising applications like biomedical sensors, point-of-care diagnostics or fast screening introduce further engineering challenges, specifically when considering a disposable element containing the analyte. The three key challenges are the strong restriction coming from limitations to approved materials for the analyte container, geometric dimensions in the mm-range common in hospital or point-of-care environment and acoustic coupling between sensor platform and analyte container.

scholarly journals Frequency-dependent variation in the two-dimensional beam pattern of an echolocating dolphin

2011 ◽  
Vol 7 (6) ◽  
pp. 836-839 ◽  
Author(s):  
Josefin Starkhammar ◽  
Patrick W. Moore ◽  
Lois Talmadge ◽  
Dorian S. Houser
Keyword(s):  
Sound Propagation ◽  
Sound Field ◽  
Spatial Separation ◽  
Acoustic Properties ◽  
Maximum Pressure ◽  
Frequency Bandwidth ◽  
Sound Sources ◽  
Pressure Peak ◽  
Prey Localization ◽  
Dominant Peak

Recent recordings of dolphin echolocation using a dense array of hydrophones suggest that the echolocation beam is dynamic and can at times consist of a single dominant peak, while at other times it consists of forward projected primary and secondary peaks with similar energy, partially overlapping in space and frequency bandwidth. The spatial separation of the peaks provides an area in front of the dolphin, where the spectral magnitude slopes drop off quickly for certain frequency bands. This region is potentially used to optimize prey localization by directing the maximum pressure slope of the echolocation beam at the target, rather than the maximum pressure peak. The dolphin was able to steer the beam horizontally to a greater extent than previously described. The complex and dynamic sound field generated by the echolocating dolphin may be due to the use of two sets of phonic lips as sound sources, or an unknown complexity in the sound propagation paths or acoustic properties of the forehead tissues of the dolphin.

scholarly journals 3D Acoustic Modelling of Dissipative Silencers with Nonhomogeneous Properties and Mean Flow

2014 ◽  
Vol 6 ◽  
pp. 537935 ◽  
Author(s):  
E. M. Sánchez-Orgaz ◽  
F. D. Denia ◽  
J. Martínez-Casas ◽  
L. Baeza
Keyword(s):  
Bulk Density ◽  
Acoustic Analysis ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Acoustic Properties ◽  
Mean Flow ◽  
Absorbent Material ◽  
Outer Chamber ◽  
Nonhomogeneous Properties ◽  
Flow Effects

A finite element approach is proposed for the acoustic analysis of automotive silencers including a perforated duct with uniform axial mean flow and an outer chamber with heterogeneous absorbent material. This material can be characterized by means of its equivalent acoustic properties, considered coordinate-dependent via the introduction of a heterogeneous bulk density, and the corresponding material airflow resistivity variations. An approach has been implemented to solve the pressure wave equation for a nonmoving heterogeneous medium, associated with the problem of sound propagation in the outer chamber. On the other hand, the governing equation in the central duct has been solved in terms of the acoustic velocity potential considering the presence of a moving medium. The coupling between both regions and the corresponding acoustic fields has been carried out by means of a perforated duct and its acoustic impedance, adapted here to include absorbent material heterogeneities and mean flow effects simultaneously. It has been found that bulk density heterogeneities have a considerable influence on the silencer transmission loss.

scholarly journals High Resolution and Labeling Free Studying the 3D Microstructure of the Pars Tensa-Annulus Unit of Mice

2021 ◽  
Vol 9 ◽  
Author(s):  
Jian-Ping Wu ◽  
Xiaojie Yang ◽  
Yilin Wang ◽  
Ben Swift ◽  
Robert Adamson ◽  
...  
Keyword(s):  
Tympanic Membrane ◽  
3D Imaging ◽  
Sound Propagation ◽  
Imaging Technique ◽  
Imaging Techniques ◽  
Acoustic Properties ◽  
Elastic Fibers ◽  
3D Microstructure ◽  
Pars Tensa ◽  
Tympanic Membranes

Hearing loss is a serious illness affecting people’s normal life enormously. The acoustic properties of a tympanic membrane play an important role in hearing, and highly depend on its geometry, composition, microstructure and connection to the surrounding annulus. While the conical geometry of the tympanic membrane is critical to the sound propagation in the auditory system, it presents significant challenges to the study of the 3D microstructure of the tympanic membrane using traditional 2D imaging techniques. To date, most of our knowledge about the 3D microstructure and composition of tympanic membranes is built from 2D microscopic studies, which precludes an accurate understanding of the 3D microstructure, acoustic behaviors and biology of the tissue. Although the tympanic membrane has been reported to contain elastic fibers, the morphological characteristic of the elastic fibers and the spatial arrangement of the elastic fibers with the predominant collagen fibers have not been shown in images. We have developed a 3D imaging technique for the three-dimensional examination of the microstructure of the full thickness of the tympanic membranes in mice without requiring tissue dehydration and stain. We have also used this imaging technique to study the 3D arrangement of the collagen and elastic fibrillar network with the capillaries and cells in the pars tensa-annulus unit at a status close to the native. The most striking findings in the study are the discovery of the 3D form of the elastic and collagen network, and the close spatial relationships between the elastic fibers and the elongated fibroblasts in the tympanic membranes. The 3D imaging technique has enabled to show the 3D waveform contour of the collagen and elastic scaffold in the conical tympanic membrane. Given the close relationship among the acoustic properties, composition, 3D microstructure and geometry of tympanic membranes, the findings may advance the understanding of the structure—acoustic functionality of the tympanic membrane. The knowledge will also be very helpful in the development of advanced cellular therapeutic technologies and 3D printing techniques to restore damaged tympanic membranes to a status close to the native.

Hysteresis curves and loops for harmonic and impulse perturbations in some non-equilibrium gases

Open Physics ◽  
2013 ◽  
Vol 11 (11) ◽  
Author(s):  
Anna Perelomova
Keyword(s):  
Wave Propagation ◽  
Internal Energy ◽  
Sound Propagation ◽  
Newtonian Fluids ◽  
Acoustic Energy ◽  
Acoustic Properties ◽  
Hysteresis Curves ◽  
First Case ◽  
Relaxing Medium ◽  
Relaxing Gas

AbstractEvolution of sound in a relaxing gas whose properties vary in the course of wave propagation, is studied. A relaxing medium may reveal normal acoustic properties or be acoustically active. In the first case, losses in acoustic energy lead to an increase in internal energy of a gas similarly as it happens in Newtonian fluids. In the second case, acoustic energy increases in the course of sound propagation, and the internal energy of a medium decreases. Variations in the internal energy of a gas are proportional to some generic parameter, the sign of which is responsible for acoustical activity, and depends on intensity and shape of the sound waveform. Hysteresis curves in the plane of thermodynamic states are plotted. Curves for harmonic and several aperiodic sound impulses are plotted, discussed and compared.

The Dispersion of Acoustic Energy in the Dissemination from the Source

2014 ◽  
Vol 899 ◽  
pp. 513-516
Author(s):  
Dušan Dlhý ◽  
Alena Pernišová
Keyword(s):  
Cross Section ◽  
Sound Absorption ◽  
Sound Propagation ◽  
Acoustic Energy ◽  
Acoustic Properties ◽  
Technological Equipment ◽  
Source Position ◽  
Energy Propagation ◽  
Sound Sources ◽  
Sound Levels

Methodology of the way of supposed sound levels calculations in closed objects areas from the sound sources is based on assumptions, that the propagation of sound is dominant. In many cases the acoustic properties of space of sound propagation have great importance. We have to take in the consideration - the size and cross-section areas of dispersion bodies, their sound absorption coefficient; - shape of area and boundary areas absorption; - position of concerning point in relation to the source position in space; - noise of technological equipment and relatively other coefficients that may effect the sound energy propagation.

Acoustic Modeling of Charge Air Coolers

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Magnus Knutsson ◽  
Mats Åbom
Keyword(s):  
Gas Exchange ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Acoustic Properties ◽  
Passenger Cars ◽  
Air Intake ◽  
Ic Engines ◽  
Reactive Properties ◽  
Good Agreement

The necessity of reducing CO2 emissions has lead to an increased number of passenger cars that utilize turbocharging to maintain performance when the internal combustion (IC) engines are downsized. Charge air coolers (CACs) are used on turbocharged engines to enhance the overall gas exchange efficiency. Cooling of charged air increases the air density and thus the volumetric efficiency and also increases the knock margin (for petrol engines). The acoustic properties of charge coolers have so far not been extensively treated in the literature. Since it is a large component with narrow flow passages, it includes major resistive as well as reactive properties. Therefore, it has the potential to largely affect the sound transmission in air intake systems and should be accurately considered in the gas exchange optimization process. In this paper, a frequency domain acoustic model of a CAC for a passenger car is presented. The cooler consists of two conical volumes connected by a matrix of narrow ducts where the cooling of the air takes place. A recently developed model for sound propagation in narrow ducts that takes into account the attenuation due to thermoviscous boundary layers and interaction with turbulence is combined with a multiport representation of the tanks to obtain an acoustic two-port representation where flow is considered. The predictions are compared with experimental data taken at room temperature and show good agreement. Sound transmission loss increasing from 5 to over 10 dB in the range 50–1600 Hz is demonstrated implying good noise control potential.

The influence of mean flow on the acoustic properties of a tube bank

1984 ◽  
Vol 396 (1811) ◽  
pp. 383-403 ◽  
Keyword(s):  
Dispersion Equation ◽  
Sound Propagation ◽  
Circular Cross Section ◽  
Cross Flow ◽  
Acoustic Properties ◽  
Mean Flow ◽  
Tube Bank ◽  
Conservation Of Energy ◽  
Trailing Edges ◽  
The Mean

The theory of sound propagation through a bank of rigid parallel tubes in the presence of a nominally steady, low Mach number cross flow is discussed. A detailed diffraction analysis is given for the idealized but mathematically tractable case of a bank of strips set at zero angle of attack to the mean flow. Various approximations for the dispersion equation governing the propagation of long waves are derived, including the influence of acoustically induced vortex shedding from the strip trailing edges and of hydrodynamic interactions between neighbouring strips. The sound is attenuated by a transfer of energy to the kinetic energy of the essentially incompressible field of the shed vorticity. It is shown how the principle of conservation of energy and a Kramers-Kronig dispersion relation can be combined to yield an alternative derivation of the dispersion equation. This procedure is applicable to a simplified model of propagation through a bank of rigid tubes of circular cross section, and an approximation to the dispersion equation is obtained in this case. The relevance of these results to bound resonances in tube bank cavities is discussed.

scholarly journals Effect of Subsurface Mediterranean Water Eddies on Sound Propagation Using ROMS Output and the Bellhop Model

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3617
Author(s):  
Seyed Hossein Hassantabar Bozroudi ◽  
Daniele Ciani ◽  
Mahdi Mohammad Mahdizadeh ◽  
Mohammad Akbarinasab ◽  
Ana Claudia Barbosa Aguiar ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Acoustic Energy ◽  
Acoustic Properties ◽  
Angular Distributions ◽  
Northeastern Atlantic Ocean ◽  
Mediterranean Water ◽  
Northeastern Atlantic

Ocean processes can locally modify the upper ocean density structure, leading to an attenuation or a deflection of sound signals. Among these phenomena, eddies cause significant changes in acoustic properties of the ocean; this suggests a possible characterization of eddies via acoustics. Here, we investigate the propagation of sound signals in the Northeastern Atlantic Ocean in the presence of eddies of Mediterranean Water (Meddies). Relying on a high-resolution simulation of the Atlantic Ocean in which Meddies were identified and using the Bellhop acoustic model, we investigated the differences in sound propagation in the presence and absence of Meddies. Meddies create sound channels in which the signals travel with large acoustic energy. The transmission loss decreases to 80 or 90 dB; more signals reach the synthetic receivers. Outside of these channels, the sound signals are deflected from their normal paths. Using receivers at different locations, the acoustic impact of different Meddies, or of the same Meddy at different stages of its life, are characterized in terms of angular distributions of times of arrivals and of energy at reception. Determining the influence of Meddies on acoustic wave characteristics at reception is the first step to inverting the acoustic signals received and retrieving the Meddy hydrological characteristics.

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