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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of the Acoustical Society of Korea
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Journal DOI :
The Acoustical Society of Korea
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Volume & Issues
Volume 27, Issue 8 - Nov 2008
Volume 27, Issue 7 - Oct 2008
Volume 27, Issue 6 - Aug 2008
Volume 27, Issue 5 - Jul 2008
Volume 27, Issue 4 - May 2008
Volume 27, Issue 3 - Apr 2008
Volume 27, Issue 2 - Feb 2008
Volume 27, Issue 1 - Jan 2008
Selecting the target year
Effects of Ultrasonic Scanner Setting Parameters on the Quality of Ultrasonic Images
Yang, Jeong-Hwa ; Lee, Kyung-Sung ; Kang, Gwan-Suk ; Paeng, Dong-Guk ; Choi, Min-Joo ;
The Journal of the Acoustical Society of Korea, volume 27, issue 2, 2008, Pages 57~65
Setting parameters of Ultrasonic scanners influence the quality of ultrasonic images. In order to obtain optimized images sonographers need to understand the effects of the setting parameters on ultrasonic images. The present study considered typical four parameters including TGC (Time Gain Control), Gain, Frequency, DR (Dynamic Range). LCS (low contrast sensitivity) was chosen to quantitatively compare the quality of the images. In the present experiment LCS targets of a standard ultrasonic test phantom (539, ATS, USA) were imaged using a clinical ultrasonic scanner (SA-9000 PRIME, Medison, Korea). Altering the settings in the parameters of the ultrasonic scanner, 6 LCS target images (+15 dB, +6 dB, +3 dB, -3 dB, -6 dB, -15 dB) to each setting were obtained, and their LCS values were calculated. The results show that the mean pixel value (LCS) is the highest at the max setting in TGC, mid to max in gain and pen mode in frequency and 40-66 dB in DR. Among all images, the image being the highest in LCS was obtained at the setting of DR 40 dB. It is expected that the results will be of use in setting the parameters when ultrasonically examining masses often clinically found In either solid lesions (similar to +15, +6, +3 dB targets) or cystic lesions (similar to -15, -6, -3 dB targets).
Quality Improvement of Low-Bitrate HE-AAC Encoder
Kim, Jeong-Geun ; Lee, Jae-Seong ; Lee, Tae-Jin ; Kang, Kyeong-Ok ; Park, Young-Cheol ;
The Journal of the Acoustical Society of Korea, volume 27, issue 2, 2008, Pages 66~74
In this paper, we propose new techniques that can improve the quality of AAC and SBR encoders comprised in low bitrate HE-AAC. To reduce the pre-echo artifacts often occurring for transient blocks in AAC, we propose an extended Temporal Noise Shaping (sTNS) in which the frequency range is selectively extended down to the low-frequency region. Also, for he high-frequency region being coded by SBR encoder, tones are identified through a sinusoidal modeling and their frequencies are adjusted within the QMF band in order to reduce the noise floor due to aliasing. Spectrograms of the decoded signals were compared and listening tests were conducted to evaluate the proposed algorithm. Results confirmed the effectiveness of the proposed algorithm.
Global Soft Decision Using Probabilistic Outputs of Support Vector Machine for Speech Enhancement
Jo, Q-Haing ; Chang, Joon-Hyuk ;
The Journal of the Acoustical Society of Korea, volume 27, issue 2, 2008, Pages 75~79
In this paper, we propose a novel speech enhancement technique using global soft decision (GSD) based on the probabilistic outputs of support vector machine (SVM). Generally, speech enhancement algorithms applied soft decision gain modification and noise power estimation have bettor performance than those employing hard decision. Especially, global speech absence probability (GSAP), which is known as an effective measure of the speech absence in each frame, has been adopted to SD-based speech enhancement methods. For this reason, we introduce a new GSAP estimated from the probabilistic output of SVM using sigmoid function. The performance of the proposed algorithm is evaluated by the PESQ and MOS test under various noise environments and yields better results compared with the conventional GSD scheme.
Diagnosis of Micro-Calcified Lesions of Breast Tissue Phantoms Using Acoustic Resonance Coupled with Power Doppler
Kim, Jeong-Koo ; Ha, Myeung-Jin ;
The Journal of the Acoustical Society of Korea, volume 27, issue 2, 2008, Pages 80~86
Breast ultrasound has many advantages over mammography but suffers from a shortcoming of being not suitable in detecting microcalcification. We studied on a method based on acoustic resonance and power Doppler to detect calcification of breast tissue using a typical 7.5 MHz linear probe used in breast ultrasound examination. We first constructed a breast tissue phantom made of gelatin and then observed calcified legions as external vibrations varied. Calcification injected to the breast tissue phantom being resonated different from the surrounding medium, and its acoustic resonance driven by external vibrations was visualized by differences for color brightness and area in ROI of power doppler. In low frequency regions, the acoustic resonance almost not appeared and showed a plateau in
and the color vanished as the frequency further increased.
Adaptive Chirp Beamforming for Direction-of-Arrival Estimation of Wideband Chirp Signals in Sensor Arrays
Kim, Jeong-Soo ; Choi, Byung-Woong ; Bae, Eun-Hyon ; Lee, Kyun-Kyung ;
The Journal of the Acoustical Society of Korea, volume 27, issue 2, 2008, Pages 87~91
In this paper, the adaptive chirp beamforming method is proposed to solve the bias problem in the direction-of-arrivals (DOAs) estimation of the wideband chirp signals which have an identical time-frequency parameter and are emanated from different directions. The source location bias results from the interferences impinging on the array from the other directions. The proposed method exploits the time-frequency structure of the chirp signal based on STMV (STeered Minimum Valiance) to improve the DOA estimation performance by minimizing the chirp interferences effectively. Simulation results show the DOA estimation performance achieved by the proposed method as compared to the conventional methods.
A Study on the Conversion Condition of Shallow Water 3-layered Model into 2-layered Model with Correlation
Kim, Young-Sun ; Kim, Sung-Boo ;
The Journal of the Acoustical Society of Korea, volume 27, issue 2, 2008, Pages 92~101
To dissolve the multi-layered model problems, and to complement 2-layered model's simplicity, assumed fluid-fluid-solid 3-layered model. Generally it is known that if the sediment thickness is more than 10 wavelength, the half space's influence to the in-water acoustic field could be disregarded. By tracking the maximum correlation coefficient of calculated results and experimental ones we confirmed that the requirement could be more realized. To calculate the maximum correlation coefficient we used single sensor transmission loss. On the assumption that the sediment sound velocity was 1813 m/s and frequency range 50 kHz to 120 kHz, the conversion condition was from 2.5 to 7.7 wavelength.