This paper deals with A-type and B-type rectangular cuboid SVU (soundproofing ventilation unit) contain an inlet and outlet in opposite surfaces.The difference between them is whether they are located in small or big cross section area.Following the theoretical calculation, the shape and location of the inlet and the outlet are determined by an investigation of the distribution of higher order mode waves formed inside the SVU.Finally, experimental results of Atype and B-type based on the reverberation chamber method are shown to be in reasonable agreement with our theoretical predictions.The results of theoretical calculation and experiments conducted lead to the conclusion that A-type is suitable for soundproof ventilation unit.
This paper is concerned with an improved network model in acoustical application to petroleum logging and seismic exploration.Utilizing acoustic-electric analogue, we report in this paper a newly developed acoustic-logging network model.Important relationships amongst various physical factors are established, i.e. driving-voltage signal, electric-acoustic conversion of source-transducer, acoustic-electric conversion of receiver-transducer, the physical and geometrical properties of propagation media, as well as the measured logging signal.Technically, a driving-voltage convolution with electric-acoustic impulse response is used to substitute for some traditionally assumed acoustic-source functions on acoustic logging, e.g.Tsang wavelet, Ricker wavelet, Gaussian impulse wavelet, etc.With an improved understanding of the anisotropic effects on reflection/refraction between two different anisotropic rock slabs, the new network model can be used to determine the various properties of signal propagation in acoustic-logging, including propagation speed, phase factor, signal amplitude, and frequency information.In turn, it provides input for analysis of amplitude variations with offset (AVO).Corresponding to the improved network model, with available logging and seismic exploration data, a new algorithm for analysis of amplitude variation has been developed to explore new oil reservoirs or gas fields.
This paper establishes a procedure for the evaluation of human hearing perception in indoor spaces by jury testing. An artificial head system was used to record indoor noise and to determine physical acoustic and psychoacoustic parameters within living and working environments. This test involved a jury consisting of 102 people of different ages, genders and occupations. The subjects participated in the sound quality evaluation and from this; indicators of human perception to sound were obtained. Three types of residential spaces in which to carry out the jury test were selected, including a high-rise apartment, a general residential apartment and a small apartment suite. A workspace in the form of a medium-sized meeting room was also tested. The paired comparison method and the category judgment method were both utilized in the jury test questionnaire. The paired comparison method was used to evaluate the psychoacoustic perception of loudness and sharpness, while the category judgment method applied a seven-point scale. Psychoacoustic parameters were used to analyze human hearing responses; from these, perceived sound quality was established for each subject. Through this testing procedure, a reasonable sound quality evaluation method was established.
A conceptual model for window manufacturing which is capable of ventilation, regulating sunlight, and reducing a traffic and environment noise has been presented in previous studies.This window combines two basic components: a soundproofing ventilation unit (SVU) and a lighting unit.The former is constructed using a rectangular cubic with input and output openings at both ends.However, when using the rectangular cubic, the indoor lighting effect could not be expected to be as great.This paper deals with a parallelepiped shape and those acoustic characteristics based on the experiments and comparisons with those of rectangular cubic SVU.
The main objective of this study was to understand the physical law characterizing dough during kneading. Throughout the process, dough is subjected to extensional deformation resulting from the mechanical component and the development of holes in the matrix. For that, we developed a very low frequency acoustic device (< 100 Hz) to follow the mechanical evolution of the dough through an in-line acoustic sensor with part of the mixer playing the role of an acoustic receiver (earphone), which exploits the background noise of the process. Depending on the physical state of the product, acoustic amplitude of sound was chosen to represent the evolution of the matter. Via a signal processing modulus this sensor shows the mechanical progress of the dough by means of a curve with critical points. The results show that the acoustic component is able to follow the evolution of the physical properties of the matter in situ. The results using various technological parameters indicate that a high degree of sensitivity can be reached with non-destructive acoustic techniques in highly absorbing media.
The high-order harmonic-wave generation of ultrasonic shear waves has not yet been studied.We generated high-order shear harmonic waves and studied them in terms of the nonlinear wave mechanism associated with strain waves.When the shear waves propagated through highly dissipative MnCu 20 Ni 5 Fe 2 , TiNi, and Sn-3Al specimens and were reflected from the far side of the specimen, we observed high-order harmonic waves up to the fifth-order of the fundamental frequency.The frequency f increases linearly with the harmonic-frequency order number n, f= a (n-1) + c.The order number coefficient a increases as Poisson' s ratio increases, suggesting that the generation of high-order harmonic waves can be attributed to anharmonic solids with large elastic deformability and high transparency for shear waves.
A time-frequency analysis, which represents the time change of a signal, is significant in all fields. Wigner distribution, a short time Fourier transform (STFT), a kernel method, and a characteristic function method etc. are known as a time-frequency analyzing method, and those methods have merits and demerits. STFT method has been used as ultrasound blood-flow imaging for a long time, because it is suitable for a non-stationary signal analysis. In this paper, I investigated how to control a time-frequency resolution of STFT, and evaluated the image quality of non-stationary signals using a point-spread function (PSF). The time-frequency resolution of an image corresponds to the aspect ratio of a pixel. Because of the uncertainty principle of time and frequency, to control the aspect ratio is not easy. The PSF is changed by the parameters, such as a frequency-range, a frequency-resolution, a time-range, a window function, a sampling frequency, etc. I propose the control method that keeps the aspect ratio of PSF constant with expansion and contraction of an image.
Many recent studies in different domains exploited the ambient noise correlation to retrieve the Green's function between two points. This technique allows a passive characterization of a given medium in the presence of a perfect diffuse field. The aim of this paper is to apply this principle in an aeronautic context. Thus we are looking to exploit the mechanical vibrations in a plane during the flight, to realize a passive structural health monitoring. Indeed, a natural acoustic noise field is produced by engines and aero acoustic effects. That being said, such a field is not spatially and temporally perfectly diffused, which yields to imperfect conditions where convergence towards the Green's function is not ensured. Despite that, in this paper we show that since the obtained information is sensible to the medium state, it is still exploitable for damage detection. In fact, experimental studies presented in this paper allow verifying two necessary conditions to the applicability of this technique: the reproducibility of the cross-correlation function, and its potential to detect a defect in the medium. Finally, the influence of the source position on the cross-correlation function is shown.
The work presents the implementation in software of an adaptive method for reducing the non-uniformity of the frequency-response-curve, by covering certain walls of small rectangular rooms, with a particular type of a passive acoustical treatment, consisting of porous absorbents covered with perforated sheets, in which each perforation behaves independently as Helmholtz resonators. The method employs new developments of another publication for finding the modal parameters, namely natural frequencies and associated damping constants, of rectangular rooms with arbitrary (uniform) wall-impedances. The adaptive software is capable of continuously improving the implemented type of acoustical treatment and would allow the implementation of new types of treatments as desired. Some testing results are presented, demonstrating the ability of the software for finding best parameters of the acoustical treatment, giving as input data the room dimensions and source/receiver locations only.
The incidence of collisions between motorcyclists and other vehicles may be significantly reduced by research that improves the acoustic awareness of cyclists, and thus heightens the ability of cyclists to respond to unexpected incursions from the surrounding traffic.We use our hearing as an early warning system, and hearing swiftly redirects our vision and attention.This shift in gaze is critical to our capacity to assess the location, direction of travel, and velocity of approaching vehicles.The present study was composed of two experiments.In the first experiment a Neumann KU-100 dummy head with embedded binaural microphones was used to measure noise levels in a motorcycle helmet as a function of velocity.Noise levels were measured in two helmets, one with active noise reduction technology, and one without.The results showed that noise levels exceeded 100 dB (A) at highway speeds in the absence of noise reduction technology.The helmet with active noise control ear muffs was able to attenuate helmet noise by up to 26 dB.Active noise control technology shows great promise for noise reduction for the motorcycle helmet industry, and the development of "quiet" helmets is important for both hearing conservation and highway safety.The second experiment surveyed subjective perceptions of helmet noise by motorcyclists.The results from the present sample showed that 92.1% of the respondents objected to the high noise levels associated with cycling, 63.5 % wore earplugs, 46.8% reported tinnitus, and 95.2% wanted a quieter helmet.
The experiment BAROC (Baltic Acoustics on Rocky Outcrops) was performed in May 2002.Analysis and modelling of part of the received data are reported here, concerning transmission loss and reverberation in a shallow-water area south of Stockholm.LFM pulses were transmitted in two directions with frequency content between 500 and 5500 Hz.In both directions a clear sound channel was observed, for which the optimum propagation frequency was about 4 kHz.Strong bottom reverberation was measured.A ray-trace model has been used as forward model for inversion of bottom parameters with a genetic algorithm.The inversion results were subsequently verified with a parabolic-equation model, and they were used to assess the level of reverberation.
A model for manufacturing doors and windows which are capable of natural ventilating, reducing traffic noise and so on for the developing tropical countries is presented.These windows and doors combine two basic components which are ventilation unit and lighting unit.Due to the fact that the ventilation unit must have a large volume to attenuate low frequency noise, many resonance of higher-order mode wave will be generated inside the unit.In this work, a method to predict the insertion-loss of rectangular ventilation unit with input and output openings at various positions is proposed by solving the wave equation, considering the resonance frequencies of higher-order mode.The results of the analysis have been confirmed by experiments.
The slim-hole acoustic-logging tool is often used for measurement while drilling and horizontal well logging.The source and receiver are generally thin cylindrical-shell piezoelectric transducers.The radius of the drilling-collar limits the size of the cylindrical-shell transducer in the logging tool.The smaller the radiation area of the transducer, the smaller the radiated acoustic energy, and the smaller its radius, the higher the frequency of the radiated acoustic signals.Besides, the attenuation for higher frequency wave propagating in the medium is higher.Due to these reasons the amplitude of the measured acoustic signal by using the slim-hole logging tool is usually much smaller than that by using the conventional logging tool.Therefore, the acoustic-beam steering technology is important for enlarging the amplitude of the received acoustic signal during logging with a slim-hole logging tool.The geometrical-size of the cylindrical-shell transducer influences the acoustic-beam steering efficiency of the logging tool with a line-array source and a receiver.In this paper, in the frame work of the acoustic-logging transmission network model with the concept of directivity-weighted coefficient, we have carried out the calculation and analysis of the effects of geometrical-size of the transducer on the acoustic-beam steering efficiency of the slim-hole acoustic-logging tool with a line-array source and a receiver.The calculated results are useful for optimizing the design of the slim-hole acoustic-logging tool with a line-array source and a receiver.
Non-linear sound propagation is investigated computationally by simulating compressible time-developing mixing layers using the Large Eddy Simulation (LES) approach and solving the viscous Burgers Equation.The mixing layers are of convective Mach numbers of 0.4, 0.8 and 1.2.The LES results agree qualitatively with known flow behavior.Mach waves are observed in the near sound field of the supersonic mixing layer computed by the LES.These waves show steepening typical to non-linear propagation.Further calculations using the Burgers equation support this finding, where the initial wave slope has a role in kicking them.No visible non-linear propagation effects were found for the subsonic mixing layers.The effects of geometrical spreading and viscosity are also considered.
Hearing is a function of the acoustic signal and the properties of the environment that structure the sound. To better understand how hearing is affected by structural properties, the current research investigated the impact of football helmets for hearing. Speech signals were broadcast at three angles of incidence (0°, 45°, or 90°) to an artificial dummyhead recording device wearing a football helmet (experimental condition) or without the helmet (control condition) to make binaural recordings using condenser microphones positioned at the location of the tympanic membrane. Acoustic analyses revealed that the helmet caused frequency-specific changes to an auditory signal, including both positive and negative interference that varied in relationship to the angle of incidence. Behavioral studies showed that while; in general, the football helmet made hearing speech more difficult, the magnitude of the decrement was a function of the amount of spectral change induced in the speech signal. Results are discussed in terms of the implications of an ecological approach to hearing and the design of helmets.
A potential-based Boundary Element Method is presented for the aerodynamic and acoustic design of propel- lers at on- and off-design point conditions. Using an adaptive method, a family of airfoil sections is selected to produce the required performance (thrust, torque and efficiency versus advance ratio) at different cruise flight levels. Climb condi- tions are also considered in order to check the off-design point performance. Once the available airfoil data have been stored in a database, the code processes the families of airfoils to generate a complete geometry for a propeller of the specified performance with an optimized noise emission. The computational scheme adjusts the blade geometry (radial distribution of chord, local sweep angle and thickness) under the control of an optimization routine. The geometric data and pressure distribution are then used in the acoustic calculation, based on the Ffowcs Williams-Hawkings equation. Re- sults are presented demonstrating the application of the technique and the resulting aerodynamic performance and noise output.
Artificial reverberator is a key element in spatial audio reproduction. This paper compares various optimal design strategies of artificial reverberators for room response simulation. From the comparison, it is hoped that guidelines for design of natural-sounding reverberators can be found. Infinite impulse response (IIR) filters such as allpass filters or comb filters are used as building blocks for the design. Early reflections of room responses are modeled by three different approaches: the traditional image method, the exponential truncation method, and network approximation method. On the other hand, comb/nested allpass filter networks are exploited for modeling late reverberations, with parameters predetermined by a genetic algorithm (GA)-based procedure. Up/down-sampling and spectral band replication (SBR) techniques are also employed to save memory storage and recover the lost high frequency portion of the reverberation. Subjective listening tests were conducted to compare the proposed artificial reverberator modules. The test results revealed that the reverberator in which early reflections are modeled by network approximation and late reverberations are modeled by comb/nested allpass filter network is superior in delivering natural-sounding reverberation among all methods.
Launch Vehicles are subject, at lift-off and during flight ascent, to acoustic and aeroacoustic loads, which are random in nature.Because electronic units are very sensitive to mid and high frequency loads, it is important to numerically predict and specify the vibration levels to be applied to units for qualification test.The general objective of the activity presented in this paper is to develop a methodology to predict mid and high frequency structure-borne transmissions in launch vehicles.As the loads of interest are random, it has been chosen to investigate energy-based modeling approaches, combined with the Finite Element Method.For energy-based modeling, the structure is divided into subsystems.For high frequency predictions, the purely numerical Power Injection Method, derived from Statistical Energy Analysis, is used to estimate the Coupling Loss Factor between structural subsystems.For the mid frequency predictions, an approach close to Statistical Energy Analysis, called Statistical Energy Analysis-Like (SEA-like), is investigated.In this approach, a relation between total energies of subsystems and input powers is established, by identifying a matrix composed of Energy Influence Coefficients.The objective of the study is to establish the methodology to compute with accuracy, using the Finite Element Method, Coupling Loss Factors and Energy Influence Coefficient.It is shown that the excitation of subsystems by 'Rain on the Roof' loads defined by the 'Influence Circle' and the Optimal Latin Hypercube methods provide accurate coupling data.A validation of the methodology on academic and industrial cases is presented.
Periodontal disease is one of the most pervasive dental diseases in older adults. It involves the loss of connective tissue attachment with subsequent destruction of tooth-supporting bone, leading to loss of teeth. Periodontal pocket depth is currently measured with an invasive manual probe, but adapting diagnostic ultrasound to this purpose can avoid the pain and inaccuracy inherent in manual probing. In this paper, 3D simulations of ultrasonic periodontal probe measurements are described, using a parallel finite integration technique which is adaptable enough to create realistic anatomical geometries. The outputs of the simulation include 3D pressure values distributed throughout the periodontal anatomy, 2D vertical cross sections of the acoustic pressure waves, and the pressure across the face of the transducer which is used to synthesize the ultrasonic echo. Experimental comparison with a simple phantom is also shown. Lastly, the energy values for different simulations are calculated from the 3D pressure values to describe the amount of energy reaching different zones, especially the junctional epithelium. The simulations as well as the energy studies show that only a small portion of the ultrasonic energy is reaching the junctional epithelium, and so sophisticated mathematical techniques are required to ultrasonically measure pocket depth.
In this paper, ultrasonic properties like ultrasonic attenuation, sound velocities, acoustic coupling constants and thermal relaxation time have been studied in hexagonal structured metals Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er) and Thulium (Tm) along unique axis at room temperature.For the evaluations of ultrasonic properties, second-and third-order elastic constants have been computed also.The peculiar behavior of these metals is found at 55° due their least thermal relaxation time and highest Debye average velocity.Dy is more ductile, stable, perfect metal in comparison to other chosen metals due to its lowest value of attenuation.So we predict that Dy is most suitable lanthanide metals for material science and engineering.
