Sound Pressure Curve Research Articles

Calculation of External Vehicle Aerodynamic Noise Based on LES Subgrid Model

A dynamic Smagorinsky–Lilly model (DSLM) subgrid model on the basis of the Smagorinsky–Lilly subgrid model (SLM) was introduced in the OpenFOAM software. The flow field of the vehicle was simulated, and the pressure coefficient and sound pressure curve of the monitoring points were compared with the wind tunnel test results. The results show that the DSLM subgrid model with a wall function can achieve high simulation accuracy. The investigation of the flow field structure revealed an intermittent detachment of the turbulent vortex after the airflow passed through the rearview mirror, thereby resulting in a violent pressure pulsation on the side window around the rearview mirror. Airflow passed through the A-pillar, separated, and reattached on the upper side window, thereby producing aerodynamic noise. The research results can serve as a good reference for the simulation and test of aerodynamic noises outside the vehicle, and for the reduction of the aerodynamic noises of vehicles.

RETRACTED ARTICLE: Virtual reality of interior noises of vehicles based on boundary element and neural networks

Interior noises of vehicles would be caused when the vibration of body panels excites the indoor air. In the paper, the vibration load of engine was obtained firstly through experiments. Secondly, the engine load was applied in the finite element model of body in white to compute the vibration velocity and realize virtual reality, indicating that the front support of the body had large vibration velocity when the frequency was lower than 60 Hz. The boundary element was then adopted to compute the interior noise and extract the sound pressure at a point near the driver’s head. Two obvious peaks were shown in sound pressure curves, at 270 and 310 Hz, respectively. The body panels that had obvious impact on the interior peak noise were determined through the panel contribution analysis, and the interior peak noise was remarkably reduced after applying sound absorption materials on these panels. Nevertheless, many more additional sound absorption materials were not always better. If a multilayer of sound absorption materials was needed, an optimal value was existed in the thickness of sound absorption material. And a great impact would be played toward the interior noise of the cabin by the reasonable selection of different sound absorption materials and their thicknesses. Finally, the neutral network (NN) was also used to predict interior noises, which was compared with the result of the boundary element. The maximum difference between the prediction values of NN and boundary element was within 5 dB, indicating that the neural network was feasible to predict the interior noise. Subsequently, the neural network method would be applied to conduct the optimization analysis for the interior noise.

Numerical optimization of vehicle noises in multi-peak frequency points based on hybrid genetic algorithm and simulated annealing

The finite element model of Body in White was built, and the corresponding modes were computed in this paper. These computational modes were then compared with experimental results. The small errors showed that the accuracy of the finite element model can satisfy the computational requirements. Based on the verified finite element model, acoustic cavities in the vehicle were extracted to build a boundary element model. Sound pressure levels at all passengers in the vehicle were then computed, compared and analyzed. Results indicated that the sound pressure curve had 6 peak noises. Using the characteristic frequency weight coefficient and field point weight coefficient, the body panels which made large acoustic contributions to the comprehensive sound field under multi-characteristic frequencies were determined. Finally, the improved genetic algorithm based on simulated annealing was used to optimize the key body panels, and peak noises at researched field points after the optimization were further computed. The computational results were compared with those of the original structure, which presented that the noise was improved at most frequency points in the spectrum and peak noises were suppressed obviously.

Optimizing the manufacturing parameters of carbon nanotubes stiffened speaker diaphragm using Taguchi method

This study developed a thermal transfer printing (TTP) technique to fabricate a carbon nanotubes (CNTs) stiffened speaker diaphragm. The self-developed TTP stiffening technique does not require a high curing temperature that decreases the mechanical property of CNTs. Therefore, the inherent strength of CNTs was preserved. In addition to increasing the stiffness of diaphragm substrate, this technique alleviates the middle and high frequency attenuation associated with the sound pressure curve of a speaker, thereby smoothing the sound pressure curve and achieving a full sound range as well as reducing bass distortion and enhancing treble clarity. Furthermore, the TTP technique can stiffen a localized area on a diaphragm substrate, thus increasing diaphragm stiffness without markedly raising diaphragm weight. The Taguchi quality engineering method was applied to identify the optimal process parameters (i.e., transfer area, stiffening pattern, coating layers, and transfer temperature). Finally, the optimal process parameters were employed to fabricate a stiffened diaphragm, which was then assembled onto a speaker. The result indicated that the stiffened diaphragm improved the smoothness of the sound pressure curve for the speaker, which produced a mid-frequency dip difference (ΔdB) of 1.9dB and an attenuation peak frequency (fpeak) of 4220Hz.

Thermal Stresses Analysis and Optimized TTP Processes to Achieved CNT-Based Diaphragm for Thin Panel Speakers

Industrial companies popularly used the powder coating, classing, and thermal transfer printing (TTP) technique to avoid oxidation on the metallic surface and stiffened speaker diaphragm. This study developed a TTP technique to fabricate a carbon nanotubes (CNTs) stiffened speaker diaphragm for thin panel speaker. The self-developed TTP stiffening technique did not require a high curing temperature that decreased the mechanical property of CNTs. In addition to increasing the stiffness of diaphragm substrate, this technique alleviated the middle and high frequency attenuation associated with the smoothing sound pressure curve of thin panel speaker. The advantage of TTP technique is less harmful to the ecology, but it causes thermal residual stresses and some unstable connections between printed plates. Thus, this study used the numerical analysis software (ANSYS) to analyze the stress and thermal of work piece which have not delaminated problems in transfer interface. The Taguchi quality engineering method was applied to identify the optimal manufacturing parameters. Finally, the optimal manufacturing parameters were employed to fabricate a CNT-based diaphragm, which was then assembled onto a speaker. The result indicated that the CNT-based diaphragm improved the sound pressure curve smoothness of the speaker, which produced a minimum high frequency dip difference (ΔdB) value.

Development of Stiffened Sandwich Vibrating for Plane Speakers

The main purpose of this paper is developed the membrane, produced exciter, selected surround, optimal design method to manufacture gamut planar loudspeakers. Used nano-carbon tubes and foam board to combine the sandwich membranes which are applied the large planar loudspeakers. The optimal sandwich membranes which are including the stiffed pattern, minimum weight and stiffness are affected high frequency sound quality and sound pressure curve. Because of the sandwich membranes such as high stiffness and strong, and has received much attention as a new material for industrial applications. This creation of flat-panel speakers has the properties of light weight, thin exciter, and broad response of frequency, and also has the live sound quality and clear. The optimal programs are used finite element analysis and Fortran software to search optimal design parameters which are optimal sound quality and smooth curve of sound pressure at the 20Hz ~ 20KHz. Therefore, the optimal manufacturing parameters are manufactured sandwich planar loudspeakers which are measured experimental sound pressure curves to compare theory values.

Optimal design of rectangular composite flat-panel sound radiators considering excitation location

The optimal excitation locations of rectangular composite sound radiation plates to produce relatively smooth sound level pressure (SPL) curves are determined using an optimal design method. In the optimal design process, the vibration of the plate is analyzed using the Rayleigh–Ritz method, the sound pressure produced by the plate is calculated using the first Rayleigh integral, and the optimal excitation location is determined using a global optimization technique. The experimental SPL curves of several sound radiators were measured to verify the accuracy of the theoretical predictions. In the determination of the optimal excitation location, the trial radius of the circular excitation force is used in the vibro-acoustic analysis to predict the theoretical SPL curve of the plate, a SPL discrepancy function is established to measure the sum of the squared differences between the SPLs at the chosen excitation frequencies and the average value of such SPLs, and a global minimization technique is used to search for the best estimate of the radius of the circular excitation force by making the SPL discrepancy function a global minimum. The optimal excitation locations of several composite sound radiators with different aspect ratios and layups are determined using the proposed method.

Development High Stiffness Ratio of Stiffened Membranes for Small Flat Speakers

This research for the membrane stiffening manufacture, thickness, weight, manufacturing parameters, stiffness and surface uniformity was discussed. The used of hand rough paper as membrane substrate, and used of roller coating, spray coating of coating methods, and it carried on membrane stiffening process of carbon nanotubes. On the increase smallest weight, it had been a large increase in stiffness, and the flat speakers sound pressure curve smoother. Used different proportion of carbon nanotubes mixture of different resin to membrane stiffening, used SEM to detect the carbon nanotubes stiffening of the membrane surface coating uniformity, even different coating of compare thickness with weight of increase percentage. It used tensile test to explore different coating methods of Young's modulus of the difference. Then, we was manufactured the small plane speaker (L33mm×W21mm×H12mm) according to the various membrane stiffening and measure the sound pressure curve, and it contrasted with computer-aided analysis software obtained the theory of sound pressure curves.

905 快/不快音響帯域に関する考察(OS5-6 オーガナイズドセッション《ライフサポートにおける工学技術》)

The Concept of Equal Sound Pressure Curve is proposed by Flecher and Munson at Bell Labs to reveal the auditory sense of human in 1930's. Later, The gap between actual and early ELC: equal Loudness Contour is pointed our especially in low frequency band less than 1kHz. AIST-JAPAN established new ELC to compensate low frequency sensitivity. The A - Chracteristics in ELC is adopted to Noise Meter. However, it is recognized there exist gap between noise level and loudness level. To investigate the gap between loudness and noise(discomfort) level, we measured the frequency related discomfort index with organoleptic assessment. Experiment result shows the discomfort index is sound pressure dependent and sensitive to aging factor.

Speaker edge and resonator panel assembly

A complex speaker edge and asymmetric resonator panel in which the acoustic vibration damping capacity of the speaker edge varies longitudinally around the speaker edge. The resonator panel has an aspect ratio of approximately 1.3:1 or more, and is composed of top and bottom panels held in spaced apart relationship by a plurality of longitudinally extending ribs extending therebetween. The ribs extend at an angle of from approximately 5 to 35 degrees to the longitudinal axis of the panel. The angle is acoustically matched to the complex speaker edge to improve the accuracy with which said acoustic vibration is reproduced. The effectiveness of the differential damping capacity of the edge in improving the quality of sound output from a speaker assembly is determined by observing the average magnitude of the excursions of the sound level pressure versus frequency curves for comparable complex and single speaker edges, particularly in the 200 to 10,000 Hertz range. The speaker edge and the angle of the ribs are acoustically matched by iteratively adjusting the edge and/or the angle in response to the quality of the sound that is perceived by a trained human ear.

Measurement of Individual Loudness Functions by Trisection of Loudness Ranges

Loudness-balance measurements with monaurally impaired subjects have shown that the shape of the loudness versus sound-pressure curve among hearing-impaired persons varies significantly. But the effectiveness of adjusting the compression characteristics of wide-dynamic-range compression hearing aids-the compression ratios, the variation of compression ratio with level, and the threshold of compression-to restore normal loudness growth for the individual patient has never been properly tested; individual loudness measurements have been too uncertain to permit meaningful individual adjustments. Recent investigators have reported standard deviations of such measurements in normal-hearing subjects of 6.4 dB and 7.8 dB. This investigation describes a method of measuring loudness function with a standard deviation in normal-hearing subjects of the order of 1 dB, both significantly lower than that of previous methods and sufficiently accurate for individual-subject adjustments. Each of nine normal-hearing subjects-seven of them inexperienced and one a 9-year-old was asked to make three successive loudness trisections within an amplitude range of 40 to 80 dB SPL, providing six points from which to plot a loudness-function curve between these limits. The individual and average curves were validated as accurate loudness functions by comparing them to the curve defined by the equation of loudness versus amplitude in current Standards. In a second validation experiment, the loudness functions of masked ears measured by trisection were compared to the loudness function of those ears measured by loudness balance between masked and unmasked ears. The difference between a loudness function based on the average of subject trisections and the loudness function defined by the ANSI Standard loudness equation was -1.92 dB at the lowest trisection level and +0.05 dB at the highest level. The standard deviations of subject responses were 1.63 dB for the lowest trisection level and 0.68 dB for the highest level, with an average of 1.1 dB. The across-subject standard deviation of the test-retest differences for three subjects was less than 1.7 dB for the first three lower level responses and less than 0.8 dB for the remaining three responses. A trisection procedure for measuring loudness function showed validity and significantly less variation than previous loudness-measurement procedures. Such a procedure, once it has been validated for hearing-impaired subjects, makes it possible to test hearing aid design and fitting strategies that are based on individual-patient loudness functions.

Viscous liquids and glasses under high pressure

The isomeric pentane system, as well as other systems, was studied as a function of pressure via Brillouin scattering. Room temperature experiments were carried out at different scattering angles in a Merrill-Bassett diamond anvil cell. The scattered light was analyzed using a nine-pass tandem Fabry-Perot interferometer. Isopentane and mixtures such as 1:1 pentane/isopentane vitrify at 7.4 GPa as determined by a change in the slope of the sound velocity vs. pressure curve, and in some cases by the onset of shear modes. From the sound velocity data and thermodynamic considerations, one can extend the equations of state for these systems to high pressure. When the acoustic shear mode is measureable, it is possible to calculate the high frequency shear modulus from the data. These calculations combined with the measured viscosity allow the determination of the shear relaxation time over a broad range of pressures.

Clinical study on sweep-frequency tympanometry--data analysis using principal component analysis

A sweep-frequency tympanometer has been developed to diagnose auditory ossicular lesions more precisely. This device measures acoustic middle ear features by changing the probe tone frequency continuously. The oscillator sweeps frequency of the probe tone from 200 to 2,500Hz 1.5 seconds. A microphone picks up the changes in the acoustic pressure and the phase in the external auditory meatus during the frequency change of the probe tone. These measurements are performed under pressures at -200 and 0 dapa, and differences of both the acoustic pressure and the phase between these two pressures are graphically displayed using a microcomputer. This device can also measure and digitally display the frequency (BHz) and the sound pressure (BdB) at the minimum point (B) of the sound pressure curve, the frequency (ZHz) at 0 crossing point (Z) of the sound pressure curve, and the frequency (PHz) and the phase difference (Pdeg) at the maximum point (P) of the phase curve. Normal ranges of these five values were obtained to establish diagnostic criteria from 200 normal ears. The normal values were as follows: BHz, 480 to 1,070Hz; BdB, -6.0 to -1.8dB; ZHz, 1,100 to 1,860Hz; PHz, 910 to 1,820Hz; and Pdeg, 16.3 to 47.9 degrees. Eight cases of ossicular dislocation and 14 cases of ossicular fixation, all of which had normal external auditory meatus and tympanic membrane, were evaluated based on these values. All the cases with ossicular dislocation and 12 cases out of 14 with ossicular fixation were correctly diagnosed.(ABSTRACT TRUNCATED AT 250 WORDS)

Sweep-frequency tympanometry: its development and diagnostic value.

This reports a newly developed tympanometric system using a sweep-frequency probe tone. For a sweep-frequency tone ranging from 220 to 2 000 Hz, measurements of sound pressure (P) and phase were performed at ear canal pressures of 0 and -200 mm H2O. The results were expressed as a sound pressure curve (P0-P-200 in decibels), a phase curve (formula: see text) and a polar curve (formula: see text) against probe tone frequency. Both the frequency at which the sound pressure curve crossed the 0-dB difference line and the peak frequency of the phase curve shifted lower than normal for ossicular disruption and higher than normal for ossicular fixation. Changes in the sound pressure curve and in the phase curve were exaggerated for ossicular disruption and limited for fixation. As the result of these, the polar curve showed an expanded type for disruption and a compressed type for fixation. A review of 220-Hz tympanograms and of the polar curves for 10 patients demonstrated that the latter permitted a better discrimination among ossicular disorders.

Studies for diagnostic method for ossicular lesions

The diagnosis of the ossicular condition, fixation or interruption, is often not achieved by the routine tympanometry. A new tympanometric system has been developed in order to improve the diagnostic value. This produces a sweep-frequency probe tone of 200 to 2000Hz and measures the sound pressure difference and the phase difference between the output and the input.An experimental study was performed using eight fresh human temporal bones. Sound pressure curves and phase angle curves were figurized against the probe tone frequency in three conditions of the ossicular chain: normal, fixation glued by dental cement, and interruption made by mechanical separation. In addition, static compliance was also obtained by the conventional tympanometry. A multivariate analysis was performed to obtain the effective variables which would be a good indicator for the change in transmission characteristics of the ossicular chain. The results showed static compliance was less valuable than other variables of the sound pressure curve and the phase angle curve. Among these variables, four were selected as the most valuable ones from the result of a discriminant analysis.These four variables were clinically applied to differentiate three groups of the ossicular pathology: staps fixation, malleus or incus fixation and incudostapedial disconnection. The internal and external check using the discriminant function were performed in forty ears, in which ossicular lesions were surgically confirmed. This resulted in a high ratio of differentiation. Thus, this system can be of great value in the diagnosis of ossicular abnormalities.

The Spectral Distribution of Sound Produced by Fibers and Fabrics in Friction

The constructional details and theory of operation of a highly stable and sensitive fiber and fabric friction sound analyzer are described. Sound pressure curves for three typical fabrics and one bulk wool are shown. Results will be described in detail in Part II.

Amplitude and Phase Measurements on Loudspeaker Cones

Amplitude and phase measurements have been made of the mechanical motion of different points on the cone diaphragm for various critical frequencies. From these the cause of various peaks and dips in the sound-pressure curve can be determined. Such information is helpful when making changes to improve the cone design.