• The Journal of the Acoustical Society of Korea
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• v.28 no.1
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• pp.70-76
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• 2009

In speech communications in noisy environments, speech intelligibility is seriously degraded due to the masking effect of ambient noise. In this paper, a new method to improve speech intelligibility in noisy environments is proposed. Based on the perception theory that the temporal envelope plays a major role in determining intelligibility, the proposed method uses a novel operation that enhances the fluctuation of band-wise temporal envelope and also contains pitch enhancement for improving speech naturalness. In addition, a new subjective evaluation scheme employing binaural listening is proposed in order to measure more reliable performance. The subjective performance measured with the proposed scheme shows that the proposed method improves both intelligibility and naturalness in various environments, whereas a function parameter can control the performance trade-off between intelligibility and naturalness.

• The Journal of the Acoustical Society of Korea
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• v.38 no.6
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• pp.651-660
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• 2019

The present study aims to find out the necessary speech sound level which can satisfy with the speech intelligibility in a noisy classroom environments. For this, auralized materials were made to undertake listening tests with 27 people. Speech intelligibility tests were carried out using both Consonant-Vowel-Consonant (CVC) and Phonetically Balanced Words (PBW) methods. Signal to noise ratio was changed by 5 dB for each test. As a result, it was found that speech intelligibilities are increasing with larger Signal to Noise Ratio (SNR). It was also found that there is a lot of difference of speech intelligibilities by SNR for syllables (CVC) with the Reverberation Time (RT) of 1.5 s. However, any significant difference was not found for words (PBW) in the case with RTs of below 0.8 s. Also, it was revealed through the 2-way analysis of variance (ANOVA) test that SNR is the only attentive factor which can affect the Korean speech intelligibilities for both PBW and CVC methods. Therefore, RTs below 0.8 s could be the acoustic criteria for classroom which can minimize the effects of noise. In the case with RTs larger than 0.8 s, much larger SNR is needed to give sufficient speech intelligibility.

• The Journal of the Acoustical Society of Korea
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• v.26 no.1
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• pp.8-15
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• 2007

Speech intelligibility of the eavesdropping sound is investigated on a acoustic cavity - glass window coupled system. 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 tile speech transmission characteristics of the cavity and window system. STI (Speech Transmission Index) based upon MTF is calculated and speech intelligibility of the vibration sound of the glass window is estimated. Speech intelligibilities by the acceleration signal and the velocity signal are compared. Finally, intelligibility of the conversation sound is confirmed by the subjective test.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.139-142
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• 1998

그 동안 TTS 음성합성의 평가 척도로 명료도(Clarity)와 자연성(Naturalness)을 기준으로 삼았다. 이제는 합성음의 평가 기준이 사람 목소리와 이해도가 되는 것이 좋겠다고 생각한다. 본 논문은 사람 목소리와 이해도라는 척도 중에서 사람 목소리에 관한 주제를 다루고자 한다. 이를 위하여 음성 DB의 합성 단위로 CVC type을 기본으로 하고, CV, VC type으로 보강한 단위를 선정하여 음성 DB를 구축하였다. 그리고 합성 알고리즘은 음색을 살리며 피치 변경이 용이한 PS-RELP 알고리즘을 제안하였다.

• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.127-134
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• 2009

In this study, possibility of the laser eavesdropping is investigated on the window glasses with various thicknesses, Glass windows are excited by maximum length sequency (MLS) signal and the vibration sound is detected by a laser doppler vibrometer. From the detected sound, speech intelligibility is objectively estimated. Speech transmission index (STI), which is based on the modulation transfer function (MTF). is calculated for the estimation. Finally, disturbing wave effect on the speech intelligibility is analysed by using an outside speaker and a window shaker attached on the glass window. The purpose of the study is to estimate the possibility of remote eavesdropping by the laser sensor and to evaluate the performance of the homemade window shaker to protect from the remote eavesdropping.

• The Journal of the Acoustical Society of Korea
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• v.32 no.3
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• pp.214-226
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• 2013

Assessing the quality of audio signals is an important consideration in making high quality sounds and various methods have been developed. This paper provides a general framework of sound quality and a technical overview of the international standard methods which are described in ITU-T, ITU-R, IEC and ANSI Recommendations in the speech intelligibility, speech quality, and audio quality areas. In addition, some recent findings and future works are included.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.279-282
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• 2001

해마다 실시되고 있는 대학수학능력시험의 듣기 평가시험에 있어서, 고사장 및 지점별 음향 성능에 기인한 레벨 편차와 명료도를 산출하여 학생 선발의 공공성과 객관성을 검토해 보고자 한다. 일반적으로 듣기 평가가 이루어지는 각 고사장은 듣기 평가 실시에 지장이 없는 고등학교 교실로 지정하고 있지만, 균등한 음 환경을 제공해야 하는 시험의 성격에 반해 학교 자체의 방송 시설을 그대로 사용하는 것은 평가의 형평성 및 객관성에 충실하지 못하게 되는 요인이 된다. 따라서, 각 고사장의 확성 시스템에 따른 음성 전달품질과 수험생간의 좌석별 음압 레벨 및 명료도를 평가하였고, 실험 결과 RASTI를 비롯한 음성 및 음절 명료도를 나타내는 파라메터에서 좌석별로 큰 편차가 있는 것으로 분석되었다.

• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.201-212
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• 2021

The present study was conducted as a pilot investigation to suggest the standards of acoustic performance for classrooms suitable for incomplete hearing people such as children under 9 years of age. Subjective evaluations such as questionnaire and speech intelligibility test were conducted to 264 students at two elementary schools in Cheong-ju in order to analyze the characteristics of the listening environment in the classrooms of the lower grades in elementary school. The survey was undertaken with a total of 264 students at two elementary schools in Cheong-ju, and investigated their satisfaction with the classroom listening environment. As a result, students responded that the most helpful information type for understanding class content is the voice of teacher. In addition, the volume of the current teacher's voice is normal, and the level of clarity is highly satisfactory. As for the acoustic performance of the classroom, the opinion that the noise was normal and the reverberation was very short was found to be dominant in overall satisfaction with the listening environment. Meanwhile, as a result of speech intelligibility test using the word list selected for the lower grade students of elementary school, it could be inferred that the longitudinal axis distance from the sound source in the case of 8-year-olds is a factor that affects speech recognition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1183-1185
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• 2016

Low bit-rate speech coder in digital speech communications synthesizes speech using vocal tract model parameters. In this case, the spectra of the synthesized speech can be much distorted since the allocated bits for the parameters are considerably limited, which results in the degradation of speech intelligibility. In this paper, we propose a speech intelligibility improvement method using stochastic spectral equalizer. This method stochastically obtains the weight vector of each speech coder using spectral ratios between original and synthesized speech, then applies this weight vector to synthesized speech. From the experiments of objective speech intelligibility tests, we found that the performance of the proposed method is better than that of the conventional method.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.487-490
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• 2002

학교 교육의 특성상 많은 부분이 교실에서의 음성정보 전달에 의해 이루어지고 있는 점을 감안하면 바람직한 청취환경의 개선이 검토되어야 한다. 또한 중${\cdot}$ 고등학교의 수학능력시험의 국어, 영어 듣기평가 및 다양한 어학 시험이 시청각 시설을 통해 이루어지고 있는 실정이므로 교실의 음환경은 매우 중요한 요소라하겠다. 본 논문에서는 음환경을 좌우하는 음원의 위치에 따라 명료 도가 어떻게 달라지는지를 실험을 통하여 검증하고, 명료도가 높고, 교실 전체에 균등한 분포를 보이는 음원의 위치를 찾아내고자 하였다. 교실 내의 음원의 위치로는 일반적으로 많이 쓰이고 있는 column(벽면 노출형)과 ceiling(천정 매입형) 위치와 임의의 음원 cluster(전면 중앙)를 선정하여 음장 파라메터를 측정한 결과 RASTI 는 세 타입 모두 $0.54\~0.55$로 값으로 근소한 차이를 보이고 있으며, 잔향시간은 ceiling>cluster>column의 순서로 나타났다. 일반적으로 잔향과 명료도와의 관계는 반비례하는 것으로 알려져 있으나, 실험 결과 잔향시간이 1.33초로 가장 긴 column 스피커의 경우 D50 값이 약 $47\%$로 가장 높은 값으로 나타났다. 이것은 column형 스피커의 경우 음원과 각 학생의 위치에 대한 평균 직접음선거리가 가장 짧기 때문인 것으로 나타났다.