• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.9 no.5
• /
• pp.129-132
• /
• 2009

Frame erasure is one of the most difficult problems in voice over IP (VoIP) networks and is a major source of speech quality degradation. In this paper, a frame erasure concealment algorithm based on nonlinear regression analysis is presented to minimize speech quality deterioration in code-excited linear prediction (CELP) based coders. We applied the proposed scheme to the ITU-T G.729 standard and obtained improved perceptual evaluation of speech quality (PESQ) scores compared to the conventional methods.

• Proceedings of the KSPS conference
• /
• 1996.02a
• /
• pp.23-40
• /
• 1996

The communicative disorders in cleft palate patients have relationship with the acoustic and He physiological phenomena. Particularily hypernasality is a parameter of cleft palate speech that has been studied by many clinicians and speech pathologists. The degree of hypernasality has been assessed by the listener,s judgement, but perceptual assessements have poor scientific reliability, so objective instruments have been needed to test hypernasality with diagnostics accuracy. This study was analyzed the nasalance score using a Nasometer for cleft palate patients. The simple vowels /a/, /i/, /e/ and the approximants /j/, /w/ were tested for the degree of hypernasality after operation. The phrases containing long and short duration times were used in this study to asses hypeernasality. Fiberopic views shows the open velopharyngeal port that resulted in hypernasality of cleft palate patients. The authors assert the important of the management of cleft palate patients.

• Korean Journal of Biological Psychiatry
• /
• v.4 no.1
• /
• pp.24-28
• /
• 1997

Visual perception is a complex process engaging many different aspects of brain functioning. Like other cognitive functions, the extensive cortical distribution and complexity of visual perceptional activites make them hihgly vulnerable to brain injury. Dectection and characterization of perceptual disorders require a careful clinical assessment as well as the application of selected neuropsychological tests. In this article we reviewed neuropsychological assessment of visual perception and constructional abilities. And the principal visuospatial disorders are discussed, the associated neuropsychiatric disorders are presented.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.6
• /
• pp.1120-1125
• /
• 2010

In the speech system, for example hearing aid as well as speech communication, speech quality is degraded by environmental noise. In this study, to enhance the speech quality which is degraded by environmental speech, we proposed an algorithm to reduce the noise and reinforce the speech. The minima controlled recursive averaging (MCRA) algorithm is used to estimate the noise spectrum and spectral weighting factor is used to reduce the noise. And partial masking effect which is one of the human hearing properties is introduced to reinforce the speech. Then we compared the waveform, spectrogram, Perceptual Evaluation of Speech Quality (PESQ) and segmental Signal to Noise Ratio (segSNR) between original speech, noisy speech, noise reduced speech and enhanced speech by proposed method. As a result, enhanced speech by proposed method is reinforced in high frequency which is degraded by noise, and PESQ, segSNR is enhanced. It means that the speech quality is enhanced.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2011.07a
• /
• pp.85-88
• /
• 2011

This paper describes a single channel speech enhancement as the pre-processor of automatic speech recognition system. The improvements are based on using optimally modified log-spectra (OM-LSA) gain function with a non-causal a priori signal-to-noise ratio (SNR) estimation. Experimental results show that the proposed method gives better perceptual evaluation of speech quality score (PESQ) and lower log-spectral distance, and also better word accuracy. In the enhancement system, parameters was turned for automatic speech recognition.

• Journal of Korea Multimedia Society
• /
• v.20 no.10
• /
• pp.1619-1627
• /
• 2017

Image hashing has been successfully applied for the problems associated with the protection of intellectual property, management of large database and indexation of content. For a reliable hashing system, improving hash matching accuracy is crucial. In order to improve the hash matching performance, we propose an asymmetric hash matching method using the psychovisual threshold, which is the maximum amount of distortion that still allows the human visual system to identity an image. A performance evaluation over sets of image distortions shows that the proposed asymmetric matching method effectively improves the hash matching performance as compared with the conventional Hamming distance.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.47-50
• /
• 2008

We propose a new method evaluating the image quality of display devices using the CIECAM02 that is the recently developed CIE color appearance model and provides an extension of the previously recommended CIE color spaces. We develop the evaluation method that quantifies the color reproduction capability, emotional gray scale (gradation), and visual perception contrast (perceptual contrast range) based on the gamut in this model.

• Journal of Information Display
• /
• v.13 no.1
• /
• pp.43-49
• /
• 2012

Depth sensitivity is considered one of the factors influencing 3D displays the most. In this paper, the perceptual 3D depth was quantitatively measured to compare the depth difference among the display devices. No difference was found in the typical display performance among the devices, but the subjective evaluation of the depth sensitivity where the disparity was varied showed that the organic light emitting diode (OLED) had the highest performance, mainly due to its almost 0% crosstalk, one of the features of OLED. Crosstalk is a form of image superposition that greatly affects the depth sensitivity. The experiment results showed that the quantitative depth sensitivity varies due to geometric factors such as disparity, viewing distance, and subjective sensitivity, depending on the display image characteristics, such as crosstalk and contrast.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.873-874
• /
• 2008

In this paper, we propose a packet loss concealment (PLC) algorithm for CELP speech coders, which is based on multiple adaptive codebooks by using comfort noise for the lost packet recovery. The multiple adaptive codebooks are composed of a conventional adaptive codebook to model periodic excitation of speech and another adaptive codebook to provide a better estimate of excitation when packets are lost in the speech onset region. The performance of the proposed PLC algorithm is evaluated by implementing it into the G.729 decoder and compared with that of the PLC algorithm employed in the G.729 decoder by means of perceptual evaluation of speech quality (PESQ). It is shown from the experiments under different burstiness of packet loss rates of 3% and 5% that the proposed PLC algorithm provides higher PESQ scores than the G.729 PLC algorithm.

• ETRI Journal
• /
• v.38 no.2
• /
• pp.366-375
• /
• 2016

This paper describes an algorithm to suppress composite noise in a two-microphone speech enhancement system for robust hands-free speech communication. The proposed algorithm has four stages. The first stage estimates the power spectral density of the residual stationary noise, which is based on the detection of nonstationary signal-dominant time-frequency bins (TFBs) at the generalized sidelobe canceller output. Second, speech-dominant TFBs are identified among the previously detected nonstationary signal-dominant TFBs, and power spectral densities of speech and residual nonstationary noise are estimated. In the final stage, the bin-wise output signal-to-noise ratio is obtained with these power estimates and a Wiener post-filter is constructed to attenuate the residual noise. Compared to the conventional beamforming and post-filter algorithms, the proposed speech enhancement algorithm shows significant performance improvement in terms of perceptual evaluation of speech quality.