• 대한음성학회지:말소리
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• 제50호
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• pp.99-110
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• 2004

The normal transmission characteristics of sound are hardly obtained due to the various noises and structural factors in a running car environment. It is due to the channel distortion of the original source sound recorded by microphones, and it seriously degrades the performance of the speech recognition in real driving environments. In this paper we analyze the degree of intelligibility under the various sound distortion environments by channels according to driving speed with respect to speech transmission index(STI) and compare the STI with rates of speech recognition. We examine the correlation between measures of intelligibility depending on sound pick-up patterns and performance in speech recognition. Thereby we consider the optimal location of a microphone in single channel environment. In experimentation we find that high correlation is obtained between STI and rates of speech recognition.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.150-155
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• 2006

Speech intelligibility is investigated on a conference room-window glass coupled system. Using MLS(Maximum Length Sequency) signal as a sound source, acceleration and velocity responses of the window glass are measured by accelerometer and laser doppler vibrometer. MTF(Modulation Transfer Function) is used to identify the speech transmission characteristics of the room and window system. STI(Speech Transmission Index) is calculated by using MTF and speech intelligibility of the room and the window glass is estimated. Speech intelligibilities by the acceleration signal and the velocity signal are compared and the possibility of the wiretapping is investigated. Finally, intelligibility of the conversation sound is examined by the subjective test.

• 음성과학
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• 제11권4호
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• pp.67-73
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• 2004

Packet loss, jitter, and delay in the Internet are caused mainly by the shortage of network bandwidth. It is due to queuing and routing process in the intermediate nodes of the packet network. In the Internet whose bandwidth is changing very rapidly in time depending on the number of users and data traffic, controlling the peak transmission bit-rate of a VoIP. system depending on the channel condition could be very helpful for making use of the available network bandwidth. Adapting packet size to the channel condition can reduce packet loss to improve the speech quality. It has been shown in [1] that a VoIP system with an AMR speech codec provides better speech quality than VoIP systems with fixed rate speech codecs. With the adaptive codec mode assignment. algorithm proposed in [1], in this paper, we performed the voice transmission experiments using the wireless LAN through the real Internet environment. Experimental results are analyzed and discussed with our findings.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1796-1798
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• 2002

Speech transmission is common in many communications systems. In this paper, a technique to reduce the total bits required for expressing the speech data is proposed for the purpose of a packet transmission. A novel coding method is derived based on the concept of finding common information in sequential speech samples. Computer simulations demonstrate that the proposed scheme reduces the total bits re- quired in PCM approximately by half.

• 한국음향학회지
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• 제13권5호
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• pp.32-39
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• 1994

전화기의 통화품질은 음량정격으로 규정하고 있으나, 이 방법은 핸드셋 전화기에만 국한되는 방법이다. 핸드 프리 전화기는 실내의 음장의 영향을 더 많이 받으므로 전송 특성뿐만이 아니라 주위 잡음, 에코, 잔향도 포함하여 평가하여야 한다. 따라서 핸드 프리 전화기의 품질을 평가할 수 있는 새로운 방법이 필요하다. Steeneken은 음성 전송 지수(Speech Transmission Index ; STI) 를 계산하여 음성 전송 특성을 평가하는 객관적인 방법을 제안하였다. 본 논문에서는 STI를 핸드 프리 전화기의 통화품질 평가 방법에 적용 가능성을 고찰하고, 고속으로 STI를 계산할 수 있는 시스템을 구현하였다. 이 시스템을 이용하여 잔향 시간이 다른 세군데의 실내에서 핸드 프리 전화기의 STI를 측정한 결과, 실내의 잔향시간이 길어질수록 STI가 감소되는 것을 알았다. 이 결과는 STI를 음장 특성을 포함하는 명료도 평가 방법에도 응용할 수 있다는 것을 시사하고 있다.

• 산업기술연구
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• 제27권A호
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• pp.55-60
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• 2007

Possibility of the eavesdropping is investigated on a conference room-glass window coupled system. Speech intelligibility analysis is performed on the eavesdropping sound of the glass window. Using MLS(Maximum Length Sequency) signal as a sound source, acceleration and velocity responses of the glass window are measured by accelerometer and laser doppler vibrometer. MTF(Modulation Transfer Function) is used to identify the speech transmission characteristics of the room and window system. STI(Speech Transmission Index) is calculated by using MTF and speech intelligibility of the vibration sound is estimated. Speech intelligibilities by the acceleration signal and the velocity signal are compared.

• 한국통신학회논문지
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• 제33권3C호
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• pp.234-239
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• 2008

For the efficient coding and transmission, the speech signal can be classified into three distinctive classes: voiced, unvoiced, and transition classes. At low bit rate coding below 4 kbit/s, conventional sinusoidal transform coders synthesize speech of high quality for the purely voiced and unvoiced classes, whereas not for the transition class. The transition class including plosive sound and abrupt voiced-onset has the lack of periodicity, thus it is often classified and synthesized as the unvoiced class. In this paper, the efficient algorithm for the transition class detection is proposed, which demonstrates superior detection performance not only for clean speech but for noisy speech. For the detected transition frame, phase information is transmitted instead of magnitude information for speech synthesis. From the listening test, it was shown that the proposed algorithm produces better speech quality than the conventional one.

• 한국통신학회논문지
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• 제18권2호
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• pp.192-201
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• 1993

통신기술이 발전함에 따라 통신망이 아날로그 전송 형태로부터 디지털 전송 형태로 바뀌고 있으며, 궁극적으로는 end-to-end 디지털 통신을 실현하는 종합정보통신망(ISDN)으로 변천하고 있다. 이러한 통신망의 변천에 따라 새로운 망의 설치 및 운용과 더불어 통신의 효율화와 선진화를 달성하기 위한 통화품질의 향상도 중요한 과제로 부각되고 있다. 또한, 새로운 디지털 음성 통신계에서는 통화품질에 영향을 주는 요인들이 기존 아날로그 형태의 음성 통신계와는 다르게 나타나기 때문에 새로운 통화품질의 조건 및 기준을 확립할 필요가 있다. 본 논문에서는 음성통신과 통화품질과의 관계를 설명하고, 디지틀 음성통신계의 통화품질을 설계하기 위한 평가 실험용 디지틀 통화모델 시스템의 설계 및 개발에 대하여 기술한다. 또한, 구현한 모델 시스템의 몇가지 활용을 제안한다.

• 한국소음진동공학회논문집
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• 제17권4호
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• pp.363-369
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• 2007

The purpose of the study is to obtain acoustical information to prevent eavesdropping of the glass window. Speech intelligibility was investigated on the vibration sound detected from the glass window of a conference room. Objective test using speech transmission index(STI) was performed to estimate quantitatively the speech intelligibility. STI was determined based on tile modulation transfer function(MTF) of the room-glass window system. Using Maximum Length Sequency(MLS) signal as a sound source, impulse responses of the glass window and MTF were determined by signals from accelerometers and laser doppler vibrometer. Finally, speech intelligibility of the interior sound and window vibration were compared under different sound pressure levels and amplifier gains to confirm the effect of measurement condition on the speech intelligibility.

• 한국소음진동공학회논문집
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• 제17권9호
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• pp.888-894
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• 2007

The speech sound is detected by the vibration measurement of the window glass. In this study, we investigate the effect of the disturbing waves by background noise and window shaker excitation on the speech intelligibility of the detected sound. Based upon Modulation Transfer Function(MTF), speech intelligibility of the sound is objectively estimated by Speech Transmission Index(STI) As the level of the disturbing wave varies, variation of the speech intelligibility is examined. Experimental result reveals how STI is influenced by the level and frequency characteristics of the disturbing wave. By using a customized window shaker for disturbing sound, we evaluate the efficiency and the frequency characteristics of the anti-eavesdropping system. The purpose of the study is to provide useful information to prevent the eavesdropping through the window glass.