Acoustic Energy Output Research Articles

Simulasi karakteristik mesin termoakustik pembangkit listrik dengan penambahan model kerugian minor dari dua segmen konis

Acoustic energy output level from regenerator segment of a thermoacoustic engine model is attenuated along it’s loop due to several conditions including minor losses. This article discusses the result of Delta EC simulation of a thermoacoustic engine model acting as simple electric power generator that inserted with two conical segments. The cone segments are capable to lower the energy loss which in turn improve the overall performance of the engine in term of nett heat to acoustic energy conversion efficiency. Combined acoustic energy loss induced by both cones is equivalent to 4.94 watts minor losses. At this condition, regenerator segment amplifies the incoming acoustic energy flow of 57.02 watt up to 93.57 watt, which is equals to 36.55 watts acoustic amplification. It leads to increasing of overall engines heat to acoustic efficiency into 14.05%, which is 1.29% higher than those at the case of without cones. This engine performance improvement addressed to smoother streamline of working fluid flow inside the loop.

Three-Dimensional Finite Element Modeling of the Singer’s Formant Cluster Optimization by Epilaryngeal Narrowing With and Without Velopharyngeal Opening

This study aimed to find the optimal geometrical configuration of the vocal tract to increase the total acoustic energy output of human voice in the frequency interval 2-3.5 kHz “singer’s formant cluster”, (SFC) for vowels [a:] and [i:] considering epilaryngeal changes and the velopharyngeal opening (VPO). The study applied 3D volume models of the vocal and nasal tract based on computer tomography (CT) images of a female speaker. The epilaryngeal narrowing (EN) increased the total sound pressure level (SPL) and SPL of the SFC by diminishing the frequency difference between acoustic resonances F3 and F4 for [a:] and between F2 and F3 for [i:]. The effect reached its maximum at the low pharynx/epilarynx cross-sectional area ratio 11.4:1 for [a:] and 25:1 for [i:]. The acoustic results obtained with the model optimization are in good agreement with the results of an internationally recognized operatic alto singer. With the EN and the VPO, the vocal tract input reactance was positive over the entire fo singing range (ca. 75-1500 Hz). The VPO increased the strength of the SFC and diminished the SPL of F1 for both vowels, but with EN the SPL decrease was compensated. The effect of EN is not linear and depends on the vowel. Both the EN and the VPO alone and together can support (singing) voice production.

Modeling fast acoustic streaming: Steady-state and transient flow solutions.

Traditionally, acoustic streaming is assumed to be a steady-state, relatively slow fluid response to passing acoustic waves. This assumption, the so-called slow streaming assumption, was made over a century ago by Lord Rayleigh. It produces a tractable asymptotic perturbation analysis from the nonlinear governing equations, separating the acoustic field from the acoustic streaming that it generates. Unfortunately, this assumption is often invalid in the modern microacoustofluidics context, where the fluid flow and acoustic particle velocities are comparable. Despite this issue, the assumption is still widely used today, as there is no suitable alternative. We describe a mathematical method to supplant the classic approach and properly treat the spatiotemporal scale disparities present between the acoustics and remaining fluid dynamics. The method is applied in this work to well-known problems of semi-infinite extent defined by the Navier-Stokes equations, and preserves unsteady fluid behavior driven by the acoustic wave. The separation of the governing equationsbetween the fast (acoustic) and slow (hydrodynamic) spatiotemporal scales are shown to naturally arise from the intrinsic properties of the fluid under forcing, not by arbitrary assumption beforehand. Solution of the unsteady streaming field equationsprovides physical insight into observed temporal evolution of bulk streaming flows that, to date, have not been modeled. A Burgers equationis derived from our method to represent unsteady flow. By then assuming steady flow, a Riccati equationis found to represent it. Solving these equationsproduces direct, concise insight into the nonlinearity of the acoustic streaming phenomenon alongside an absolute, universal upper bound of 50% for the energy efficiency in transducing acoustic energy input to the acoustic streaming energy output. Rigorous validation with respect to experimental and theoretical results from the classic literature is presented to connect this work to past efforts by many authors.

Production of acoustic waves from pulsed thermal radiation

Generation of acoustic waves from a pulsed thermal radiation beam was experimentally investigated in this paper. Unlike other TACs (thermal acoustic converters), acoustic wave frequencies and phases of this type of TACs can be easily adjusted and controlled—a feature essential to the synchronization of TACs in an array. The TACs we developed were made up of a cylindrical aluminum housing, a glass cover, and metallic wool for effective thermal-to-acoustic energy conversion. Radiation emitted from an infrared heater was chopped at a constant frequency prior to entering the converter through the glass cover. The metallic wool was periodically heated by the pulsed radiation beam and cooled because of heat losses to the surroundings. Experiments were conducted for different converter designs and metallic wools, as well as different chopper speeds and radiation intensities. The amplitudes of generated sound waves were found to be dependent on the radiation intensity, the grade and properties of the metallic wool, and the cooling rate of the wool. Higher radiation intensities and thinner wools of lower thermal conductivity produced sounds of higher amplitude. More effective cooling of the metallic wool also helped. Acoustic energy output can also be enhanced by reducing the amount of air in the converter. Copyright © 2015 John Wiley & Sons, Ltd.

Optimization of Operational and Constitutional Geometric Parameters for Thermoaoustic Energy Output

The effects of geometric parameters (stack position, stack length, resonator tube length) and varying input power over acoustic energy output were investigated. The acoustic laser kit (Garret 2000) was used for the construction of TA lasers. A series of sound pressure level measurements in different orientations did not differ significantly confirming that the sound wave generated could be assumed as a spherical wave. An increase in acoustic pressure was recorded with respective increase in input power, stack and resonator tube lengths owing to their relative influence over heat transfer rate and critical temperature gradient across the stack.

Acoustic energy output and coupling effect of a pair of thermoacoustic lasers

SUMMARY Two identical TA (ThermoAcoustic) lasers were constructed, tested, and characterized for the generation and manipulation of high-amplitude acoustic waves from heat. Pyrex glass tubes with one open end and ceramics used in automobile catalytic converters were employed to fabricate the TA lasers. The ceramic stack in each TA laser was heated by a thin NiCr (nichrome) resistance wire at one end, and cooled at the other end by radiation and natural convection of atmospheric air. Generated acoustic energy and sound waves were analyzed for different power input rates and laser position arrangements. Changes in wave amplitude and phase difference due to triggered excitation and cross talking between the two TA lasers were investigated. Also tested and characterized were the focusing and synchronization of the two laser outputs for manipulating the acoustic waves and energy intensity. Direct applications of large quantities of acoustic energy generated by multiple TA lasers were addressed. It was found that the sound waves generated by a pair of identical TA lasers were almost 180° out of phase when the openings of the two lasers were very close to each other, resulting in much lower sound energy levels at the focusing point. When the two lasers were placed far apart, the phase difference between the two laser outputs varied with time. Amplitudes of both sound waves increased slightly when the two laser outputs were in phase. Copyright © 2011 John Wiley & Sons, Ltd.

Littoral Acoustic Demonstration Center 2003 seismic calibration experiment: Modeling acoustic energy distribution from seismic exploration array

In the summer of 2003 the Littoral Acoustic Demonstration Center (LADC) conducted a calibration experiment to measure the acoustic energy output of an industrial seismic exploration array in a frequency range up to 25 kHz. A standard acoustic propagation model, RAM (Range-dependent Acoustic Model by M. Collins), was adapted to model the broadband (up to 1000 Hz) waveguide transfer function for a 21-element moving seismic exploration source array generating acoustic data. Notional source signatures for each airgun in an array were generated by the calibrated airgun modeling package Gundalf, which is based on original theoretical work by Ziolkowski, Hatton, Laws, and others. The package allows modeling of the very close bubble interactions from each airgun in an array. Experimental and simulated data demonstrate good agreement in the frequency range up to 300 Hz. Factors responsible for the discrepancies between measured and modeled data in the higher frequency region are discussed. Environmental implications of variations in the acoustic energy distribution with seasonal and geographic changes in the propagation environment are addressed. [Research sponsored by the Industry Research Funding Coalition through the International Association of Geophysical Contractors.]

Apparatus for the redistribution of acoustic energy

An apparatus (1) for the redistribution of acoustic energy is provided which comprises a base (10), a lens (30), and a means for mounting a lens upon the base. The front surface of the lens includes a reflective surface. Acoustic energy output from a transducer (60) is redistributed by the apparatus (1).

Physical Factors Affecting the Cost and Efficiency of Sound Production in the Treefrog Hyla Versicolor

The metabolic cost, energy output and efficiency (i.e. the ratio of energy output to metabolic cost) of sound production were compared among male grey treefrogs (Hyla versicolor) as a function of body size and temperature. The effects of call length (in notes per call) and dominant frequency (in kHz) were also considered. Cost, determined from the amount of oxygen consumed, averaged 12.1 mJ per note and was dependent only upon body mass. Acoustic energy per note, determined from oscillograms of recorded calls, averaged 0.34 mJ and was dependent only upon temperature. Conventional theory suggests that the efficiency of sound production should be a function of the ratio of the linear size of the radiating structures to the wavelength of the sound generated (i.e. efficiency is assumed to be a function of the product of mass(0.33) and frequency), but efficiency in H. versicolor was found to be a function of the product of temperature(2.1) and mass(-1.08). Adjusting for temperature and body mass, the efficiency of sound production in H. versicolor (average 2.4 %) is greater than the efficiency of other frog species for which data are available. Temperature may affect acoustic energy output because trunk muscle contraction speed increases with temperature, which increases the velocity of airflow across the vocal cords.

The Thermal Starting Plume as an Acoustic Source

We propose that solar acoustic oscillations are excited by localized cooling events and new downflow-plume formation at the solar surface. The excitation process involves, in successive stages, radiative cooling, buoyant acceleration, and advective inflow. Pressure fluctuations induced at each stage result in monopolar, dipolar, and quadrupolar acoustic emission. We examine this excitation mechanism in detail, measure the acoustic energy output by such events, and discuss possible observational implications for helioseismic spectra.

The assessment of nasality with a nasometer and sound spectrography in patients with nasal polyposis

With the development of computerized acoustic analysis systems, an objective measure of nasal speech has become readily available by means of a simple, noninvasive technique. In this study, we assessed the nasality in patients with multiple nasal polyposis before and after endoscopic sinus surgery. With the nasometer, we measured nasalance, which reflects the ratio of acoustic energy output of nasal sounds from the nasal and oral cavities, and the slope score of the nasogram curve. The nasalance scores of nasal sentences and the slope scores of the nasogram curves for all nasal consonants were significantly lower in patients with nasal polyposis than in healthy subjects. After surgery, however, the nasalance and slope scores increased significantly to the normal range. On the sound spectrographic analysis, the frequencies of the first nasal formant decreased slightly and the sound intensity increased slightly for all nasal consonants after surgery. However, no significant change was noticed in the frequencies of the second nasal formant. In conclusion, nasometric and sound spectrographic analyses are considered to be useful tools for objectively assessing the extent of nasality in patients with nasal airway obstruction. (Otolaryngol Head Neck Surg 1997;117:343-8.)

Method and apparatus for controlling the sound field in auditoriums

A system for controlling the second field in auditorium having the feature that stage and audience seating areas are different acoustically, which includes a first assisted acoustics system whereby acoustical energy from the stage area is input, and then controlled acoustic energy is supplied to the audience seating area, and a second assisted acoustics which is provided independently of the first electronic acoustical augmentation system, whereby acoustical energy from the audience seating area is input, and then controlled acoustic energy is supplied to the stage area. Each assisted acoustics system includes acoustic energy input devices and acoustic energy output devices whereby a uniform rate of power decay coefficient can be effected throughout the hall, including spaces under balconies and the like. Significantly improved the degree of acoustic similarity between the stage area and audience seating area is achieved by controlling reverberation characteristics.

Shock wave source for generating a short initial pressure pulse

A shock wave source has a coil carrier, a planar or concave coil, a membrane consisting of electrically conductive material and a foil consisting of electrically non-conductive material. The membrane is disposed between the coil and the foil so as to be held tightly therebetween but having a perimeter which is capable of substantially unrestrained movement. Upon the application of a high voltage pulse to the coil, the resulting field causes the membrane to be rapidly repelled, however, only the mechanical forces of the membrane act on the foil, with no electromagnetic forces generated by the coil acting on the foil. The resulting pressure pulse is intensified to form a shock wave pulse in a transmission medium adjacent to the foil. The substantially unrestrained perimeter of the membrane disposed between the coil and the foil permits an initial pressure pulse of short duration to be generated, which provides the further advantages of a short approach path, a small focus zone, a high focusing factor, low electrical and thermal stress on the shock wave source and a low acoustic energy output into the body of a patient receiving treatment using the shock wave source.

Borehole acoustic transmitter

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An acoustic emission energy analysis and its use to study damage in laminated composites

A new technique which uses the output of a true RMS voltmeter to measure the acoustic emission energy output of a transducer is presented. To demonstrate its use in a typical case, this procedure is used to measure acoustic emission energy during tensile tests on [0°/±30°/90°]s glass-epoxy laminate uniaxial and 10° off-axis tensile coupons. The test results were compared with numerical predictions of laminate response and acoustic emission energy. The experiments indicate that acoustic emission energy can be used to indicate the onset of ply and interlaminar failure.

The measurement and analysis of active system acoustic impedance

A considerable part of the structure borne vibration in small aircraft is caused by both mechanically and acoustically induced vibration from the aircraft engine. The measurement method suggested within this work obtains the acoustic impedance of an active acoustic source; particular emphasis will be placed on the measurement procedure and apparatus for acquiring the source impedance characteristics of an internal combustion engine. The acoustic impedance is directly used to identify a mismatching impedance and when physically implemented with the acoustic source eliminates much of the acoustic energy output. This project utilized a two sensor sampling technique for obtaining the acoustic impedance of an active acoustic system. The two sensor method of analysis incorporates a Digital Signal Analyzer system to calculate incident‐reflected acoustic properties. The laboratory method of experimentation includes exposure of the engine to a broadband random noise while performing sensor signal analysis using a transfer function technique. [Work supported by Nelson Industries, Inc.]

Sound energy calculation of transient sound sources by the radiation efficiency method

In this paper theoretical arguments are presented to show that the radiation efficiency method can be used to calculate the sound energy radiated by transient sound sources. Radiation efficiency method results are shown to be strictly applicable to transients as well as steady state. An example is presented to illustrate that for machines of even relatively high damping the radiation efficiency for a transient can be approximated by its value at the ringing frequency, thus permitting simple calculation of acoustic energy output from time-domain data alone.

Acoustic energy output of a transducer unit

The acoustic energy output of a magnetostrictive transducer unit has been observed by the calorimetric method. The object was to observe the energy output of the unit from low to high ultrasonic intensities under identical conditions of transducer frequency and acoustic load. The design and construction of the calorimeter and its mode of operation are discussed in some detail.

Acoustic Implications of Interspecies Communication

When, in interspecies exchange of information, the dominant modes of the communication are vocal and acoustic, some of the physical limitations imposed upon the communication are shown by the hearing curves and the acoustic energy output curves. Additional limitations are shown in the difference frequency limen curves and in certain time-pattern perception limitations. One such communication system is the interlock or feedback between a single individual Homo sapiens (Hs) and a single individual Tursiops truncatus (Tt). The speech output of Hs was measured with a high-frequency microphone; detectable amounts of energy were found above the generally accepted speech band, up to the order of 60 kc. This high-frequency energy is detectable by Tt as is shown by its hearing curve from 400 Hz to 160 kHz. The usually accepted limits for Hs-Hs transmissions for 100% intelligibility are from approximately 100 Hz–10 kHz. The Hs-Hs feedback control thus is limited to approximately 10 kHz; i.e., energy above this limit is not controlled nor used by Hs. In the Hs-Tt transmission, this energy functions as an adequate stimulus to Tt. Thus, to Hs this high-frequency energy is unknown noise but can be mistaken by Tt for signals. Further consideration of the physical limitations on Hs-Tt vocal exchanges are considered with a feedback diagram and quantitative calculations based on the hearing curves and the sonic-ultrasonic output of Hs and Tt. Thus, in treating another species with a different hearing curve and a different sonic energy output, it is imperative to have quantitative physical measures in order to find channels that are adequately open both ways between the different species. Such considerations determine necessary acoustical and electrical transforms of the outputs and inputs from and to each member of the different species. [Work supported in part by AFOSR and NIH, NINDB.]

Soft Curd Character Induced in Milk by Intense Sonic Vibration

Summary Reduction in the curd tension of milk was accomplished by flowing the fluid in a thin layer over electromagnetically driven diaphragm sources of intense sonic vibration. A study was made of the curd reducing effectiveness of oscillators operating at 1100, 1200, 2160, 3000, 610, and 360 cycles as related to original curd tension of the milk, temperature, time of exposure (velocity of flow), acoustic energy output, and variations in the mechanical features of the apparatus. The percentage reduction in curd tension was greatest in hard curd (60 grams and more) milks. Final curd values approached a constant level in the soft curd range no matter what the original curd texture. No reduction in curd tension was obtained in milk treated below 18° C. and very little at temperatures below the melting point of butter fat. It was found that one of the oscillators (360 cycle) was most efficient when the milk flow was maintained at 250 gallons per hour. With a sound output of about 900 watts more than 50 per cent reduction was attained. With the 360 cycle oscillator the degree of reduction in curd tension was found to bear a direct linear relationship to the power input up to 2000 watts when the velocity was 250 gallons per hour. This represents an output of about 18 watts per one per cent decrease in tension. Other oscillators at different frequencies showed much the same effectiveness with equivalent outputs per unit volume of milk. Hence differences in frequency were found to be negligible within the range explored. A direct relationship was found to exist between degree of fat dispersion and degree of curd tension reduction. The increased number of fat particles was shown to influence curd texture by weakening the curd matrix and by providing increased adsorptive area on which protein was fixed. Since but a small proportion of the total fat in milk need be finely subdivided to reduce the curd tension, a method was devised for producing soft curd milk by vibration without impairing the final cream volume.