• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1448-1451
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• 2021

In this paper, 3D range sensor is applied to the sensor-based widerange microphone system for lectures. Since the 2D range sensor measures the shortest distance of the speaker, an error occurs and the performance is degraded. The 3D sensor provides a 160×60 distance image so that the position of the speaker can be obtained with accuracy. We propose a method for obtaining the distance per pixel required to determine the absolute position of the speaker from the distance image. The proposed array microphone system using the 3D sensor shows the improvement of 0.8~1.5dB compared to the previous works using 2D sensor.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.4
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• pp.611-614
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• 2021

In this paper, we propose a widerange array microphone for lecturer tracked with Frequency Modulated Continuous Waveform (FMCW) radar sensor. Time Difference-of-Arrival (TDoA) is often used as audio tracking, but the tracking accuracy is poor because the frequency of the voice is low and the relative frequency change is large. FMCW radar has a simple structure and is used to detect obstacles for vehicles, and the resolution can be archived to several centimeter. It is shown that the sensor is useful for detecting a speaker in open area such as a lecture, and we propose an wide range 4-element array microphone beamforming system. Through some experiments, the proposed system is able to adequately track the location and showed a 8.6dB improvement over the selection of the best microphone.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.5
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• pp.808-811
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• 2022

In this paper, a wide-range microphone system for lectures using dual 3D sensors is proposed. A previous work using a single sensor had lowering the detecting threshold to support wide-area. However it was found that an error occurred when lecturer wears clothes with low reflectivity or has small body size. When multiple sensors are used to expand the coverage it could be cause various problems. Each sensor could show different distance to the same target. We derive the rotation angle and and compensate for lecturing microphone system using sensors on the line. The proposed method shows a little improvement in performance by about 1dB compared to the previous works but the performance is uniform in all areas regardless of reflectivity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.735-741
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• 2003

A simplified view of array design and application process was introduced. Array design is critical to achieve a successful phased array measurements. A planar microphone array is designed to produce optimum performance and also to fit economic requirement in integrating data acquisition system. Certain performance characteristics are of primary concern when designing arrays. These characteristics include array resolution, spatial aliasing and array sidelobe suppression. Every array has its directional pattern that shows such characteristics. Assuming that a monopole source is located in center, beam-patterns have been simulated varying measurement conditions such as number of sensors. array aperture size, distance between array and source, frequency of interest and so on. Sensor correction was conducted on very channel using magnitudes and phased of FRF with respect to a reference microphone channel. Then with a spiral type array, measurements have been made with two point sources of same frequency in order to investigate array resolving abilities. It is observed that higher frequency source achieves better resolution than lower one does.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.31-36
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• 2014

A study on the indoor positioning system has been active recently for the location based service indoors. In the 3 dimensional positioning system based on the acoustic signal and TDOA technology, the error characteristics of the estimated source position would be changed depending on the number of microphones and the pattern of the microphone array. In this paper, the estimated position error according to the measured distance error between the microphones and the signal source is analyzed, and the optimum microphone array is decided considering the estimated position error patterns and the total amount of the estimated position error.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.484-488
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• 2007

In this paper, the measurement system using the microphone array developed for analyzing cabin noise of the vehicle and its applications are discussed. The sensor is a three dimensional microphone array, the microphones and cameras are equipped on the rigid sphere. The cameras are used for acoustic visualization. As applications, the experiments in both reverberation chamber and anechoic chamber are discussed. These results show that this system is very useful to evaluate or improve the vehicle sound insulation performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.54-60
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• 2005

In this Paper, an adaptive microphone array system with self-delay estimator is proposed. By showing that the adaptive blocking matrix (ABM) of the generalized sidelobe canceller (GSC) can estimate the relative time delay between each sensor, the proposed system utilizes the ABM not only for blocking target components in the blocked signal path, but also for estimating the relative time delay. Therefore, the proposed system requires only the GSC structure while maintaining the system performance similar to the conventional system using an additional time delay estimator as a preprocessor. Simulation results show that the performance of the proposed system is identical to the conventional system that uses an additional time delay estimation module.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.10
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• pp.256-263
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• 2014

We have designed and made three kinds of FBG(Fiber Bragg Grating) Acoustic Transducer using Hopper type WDM on the use of recently developed FBG in Korea. The newly designed three kinds of FBG Acoustic Transducer using Hopper type WDM have an excellent merit of practical use with simple structure of sensors arm as well as the merit with existing fiber sensors. It was possible to detect sound waves in the range of 10 Hz to 18 kHz through the newly designed three kinds of FBG Acoustic Transducer and also, possible to detect its signal within the maximum range of 8.6 m by the use of most suitable resonance condition of the transducer. Especially, we can expect the utilization of low-frequency signal detection instead of existing acoustic sensor in the environment of electric noise and inferior condition. Furthermore, they can be developed as the high-sensibility and multi-point signal detection system through the sensor array system.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1993-2001
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• 2006

The piezoelectric bimorph film, which, as an actuator, can generate more effective displacement than the usual PVDF film, is used to control the turbulent boundary-layer flow. The change of wall pressures inside the turbulent boundary layer is observed by using the multi-channel microphone array flush-mounted on the surface when actuation at the non-dimensional frequency $f_b^+$:=0.008 and 0.028 is applied to the turbulent boundary layer. The wall pressure characteristics by the actuation to produce local displacement are more dominantly influenced by the size of the actuator module than the actuation frequency. The movement of large-scale turbulent structures to the upper layer is found to be the main mechanism of the reduction in the wall- pressure energy spectrum when the 700$700{\nu}/u_{\tau}$-long bimorph film is periodically actuated at the non- dimensional frequency $f_b^+$:=0.008 and 0.028. The biomorph actuator is triggered with the time delay for the active forcing at a single frequency when a 1/8' pressure-type, pin-holed microphone sensor detects the large-amplitude pressure event by the turbulent spot. The wall-pressure energy in the late-transitional boundary layer is partially reduced near the convection wavenumber by the open-loop control based on the large amplitude event.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.10 s.241
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• pp.1119-1129
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• 2005

A new measurement system of wall pressure fluctuations on a rotating machinery, composed of digital recording device, was developed and evaluated. The small-sized digital recording device was attached on the rotating machinery and then was detached for data reduction. In order to obtain the system transfer function of the digital recording system, a dynamic calibration was performed utilizing the signal from a 1/8 inch B&K microphone as input. The time history of the unsteady pressure was then reconstructed from the output of the sensor by using this transfer function. The reconstructed pressure signals showed good agreement with the reference signal in both temporal and spectral sense. This sensor was then used to measure the wall pressure fluctuations on a rotating blade. An array of microphones were installed on the blade in the circumferential and radial directions. Various statistical moments were obtained from the measurement data set. Comparison of these quantities with the existing studies demonstrated satisfactory agreement. These tests give credence to the relevance and reliability of this device for applications in more complicated turbulent rotating machineries.