• Journal of the Korea Convergence Society
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• v.9 no.4
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• pp.143-150
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• 2018

This work conducted the experimental analysis on ultrasonic acoustic matching in order to measure the accuracy of gaseous fuel level values. The experimental devices were used as 12V-DC supply, control T1 board, oscilloscope (DS01072B), ultrasonic probe and pattern table. The research models were designed by ceramic assay which can determine the transmitting and receiving energies. The result of the ringing area could verify the increased characteristics in the order of D (0.180m) < E (0.184m) < B (0.204m) < A (0.234m) < F (0.244m) < C (0.247m) models based on initial 2.9V of the maximum peak voltage. From the experimental results, the model designed by Ø21*3+2t of the matching layer was notable in that the most outstanding directivity energy could be created.

• The Journal of the Acoustical Society of Korea
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• v.28 no.6
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• pp.491-498
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• 2009

This paper presents the design method of an impedance matching network using an isolation transformer and the Chebyshev filter function for the high efficiency and the flat power driving of an underwater acoustic piezoelectric transducer. The proposed impedance matching network is designed for minimizing the reactance component of transducer and having the flat power response in the wide frequency range. We design a low pass filter with ladder-type circuit using the Chebyshev function as standard prototype filter function. In addition, we design the impedance matching network which is suitable for the equivalent circuit of transducer and the turn ratio of transformer through the bandpass frequency transformation. The proposed method is applied to the simulated dummy load of the tonpilz-type transducer operating in the middle frequency range. The simulation results are compared with the measured characteristics and the validity of the proposed method is verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2487-2495
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• 2000

The acoustic characteristics of expansion chamber will be changed with the variation of inlet/outlet location due to the higher order acoustic mode in a high frequency in which the plane wave theory is not available. In this paper, the acoustic performance of reactive type expansion chamber with circular cross-section is analyzed by using the modified mode matching theory. The sensitivity analysis of four-pole parameters with respect to the location of inlet and outlet is also suggested to increase the acoustic performance. The acoustic power transmission coefficient is used as cost function, and the location of inlet and outlet is used as design variables. The steepest descent method and SUMT algorithm are used for optimization technique. Several results showed that the expansion chamber with optimally located inlet/outlet had better acoustic performance than concentric expansion chamber.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.727-729
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• 1992

In this study, the piezoelectric composites with 1-3 connectivity have been studied. A piezoelectric ceramics PZT prepared by Flux method is used as a filler in a epoxy Eccogel polymer matrix. The piezoelectric coefficients were increased as PZT volume% increases, and resonance frequency was moved to lower frequency as the sample thickness increased. The acoustic matching impedance with water is lowered than single phase PZT ceramics.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.748-754
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• 1999

The acoustic performance of reactive type single expansion chamber can be calculated theoretically by plane wave theory. But higher order modes should be considered to widen the frequency range. Munjal has suggested the method for analyzing the acoustic properties of simple expansion chamber with taking into consideration of higher order mode of inlet/outlet. But his method cannot predict the acoustic properties exactly when the dimensions of inlet/outlet and expansion chamber have not integer multiples. In this paper the new method was suggested to overcome the shortcomings of Munjal's method The predictions by this method were also compared with those by the finite element method.

• The Journal of the Acoustical Society of Korea
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• v.40 no.5
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• pp.408-416
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• 2021

In the ultrasonic dispersion, in order to avoid direct contact of the radiation surface of ultrasonic transducers with a liquid sample, the liquid sample is separated by a glass container and it receives ultrasonic energy through an acoustic medium. The transmission efficiency of the ultrasonic energy in the multi-layered ultrasonic system is an important factor. In this study, we suggested a method that can improve the ultrasonic energy transfer efficiency by using a propylene glycol solution as a liquid matching layer in the multi-layered acoustic system. In this method, a propylene glycol solution was filled between the Langevin-type ultrasonic transducer and the luminol solution and the sonoluminescence phenomena in the luminol solution, which is caused by nonlinear effect of high power ultrasound radiated from the transducer, was examined by using a Photo Multiplier Tube (PMT). The transmission efficiency depending on the concentration of propylene glycol solution was observed, and we can see that as the concentration of the propylene glycol solution increased, the matching effect increased while the acoustic attenuation increased. It was confirmed that there is an optimal concentration compromised these two conflicting conditions, and the optimum concentration of the propylene glycol solution was determined experimentally.

• The Journal of the Acoustical Society of Korea
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• v.12 no.3
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• pp.43-48
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• 1993

This study was carried out to verificate the possibility of using the laboratory setting psycho-acoustic experiment compared with the field and to delineate the appropriate indices in evaluating the Noisiness of road traffic noise by means of psycho-acoustic method. Reviewing the typical patterns of traffic noises depending upon the shapes ad conditions of the road, the road traffic noises in several representative points in the major residential areas in Kwangju city were recorded and reproduced with the noise levels modified in various steps. With these 20 sound sources, psycho-acoustic experiments in the laboratory were performed on 11 volunteer subjects. And then, psycho-acoustic experiments in the real field were performed on 10 volunteer subjects to compare the results of the laboratory experiment, the results are summerized as follows : 1. The psycho-acoustic experiments in the laboratory elicited the data well matching with those obtained in the field, resulting in even higher corelation levels. This indicates that the field assessement of responses to the noise can be replaced by the evaluatioin in the laboratory settings which render many variables easily controlled and that the responses of the residents to the noise can be easily predicted in the laboratory by applying this method. 2. Also among the complex indices, such as Noise Pollution Level or Annoyance Index high correlations were detected. On the other hand, low corelations were noted among Traffic Noise Index. 3. Highly significant correlations were found among the direct indices such as Leq, L\sub 10\, On the other hand, low correlations were detected among L\sub 50\.

• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.82-89
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• 1996

Application fields of ultrasonic transducers can be divided into two categories, a high ultrasonic resolution required field and a high ultrasonic power required field. This paper is aimed to determine the optimal properties of the matching layers of the transducer for each of the applications. Further, it is aimed to optimize the properties of the matching layers that show satisfactory performances for both of the application fields. Through the direct time domain analysis of the transmission and reflection behavior of the ultrasonic wave, apart from the conventional equivalent circuit analysis, and Fourier transformation of its results, we found the optimum acoustic impedances of the matching layers. The newly determined layers provide much better transducer performance-57% at most-than those obtained with conventional design methods. Based on the results, we also found the optimal acoustic impedances of the layers good for both of the application fields. For te optimization, we developed a new transducer performance evaluation parameter that can be applied to any type of ultrasonic transducers.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.591-595
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• 2000

Sound absorbing characteristics of poroelastic materials is known to be greatly affected by high intensity acoustic waves. However, this effect has not been considered yet. In this study, the extended semilinear model based on Biot's theory for the porous materials and the characteristics of nonlinear waves in poroelastic sound absorbing materials were introduced. The expressions for the finite-amplitude acoustic plane waves were presented. By combining each nonlinear wave with appropriate matching conditions, we could investigate the effects of finite-amplitude acoustic waves on absorption characteristics of poroelastic materials. In the most ideal case considered in this paper, the absorption coefficient was found to become larger than that of linear incident waves. It was shown that the absorption coefficient became greater especially as frequency goes higher and as distance from the source goes larger. These phenomena may be inferred to result from 'dissipation effects due to nonlinearity'. This finding may have important implications for high intensity noise control.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.3
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• pp.312-322
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• 1999

A ultrasonic transduce with a single acoustic matching layer has been designed as an attempt to increase the bandwidth of underwater transducer. The wideband resonance condition was accomplished by attaching a single matching layer on the front face of a ceramic resonator composed of a piezoelectric bar, a taper part and a head part. A modified Mason's model was used for the performance analysis and the design of transducers, and the constructed transducers were tested experimentally and numerically by changing the impedance and thickness of the matching layer in the water tank.The obtained results are summarized as follows:1. Measured resonant and antiresonant frequencies of the piezoelectric transducer with no matching layer in air were 24.7 kHz and 25.6 kHz, respectively. 2. Two resonant frequencies of the piezoelectric transducer with a single matching layer were 21.7 kHx and 26.9 kHz, respectively, in air and 21.4 kHz and 22.7 kHz, respectively, with a water load.3. Two distinct resonance peaks in the transmitting voltage response(TVR) of the developed transducer were observed at 22.0 kHz and 25.8 kHz, respectively, with center frequency of 24.0 kHz. The values of TVR at these frequencies were 130.1 dB re $1 \muPa$/V at 22.0 kHz and 128.5 dB re $1 \muPa$/V at 25.8 kHz, respectively.Reasonable agreement between the experimental results and the numerical values was achieved.