• 한국멀티미디어학회논문지
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• 제21권9호
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• pp.1068-1075
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• 2018

We propose a method for driving loudspeakers from class D audio power amplifiers in current mode, instead of in conventional voltage mode, which was impossible with the feedback circuitry. Unlike analog audio amplifiers, Class D audio power amplifiers have signal delay between the input and output signals, which makes it difficult to apply the feedback circuitry for current-mode driving. The idea of the pre-distortion scheme used for the compensation of the non-linearity of RF power amplifiers is adapted to remedy the impedance variation effect of the loudspeakers for current driving. The method uses the speaker model for the pre-distorter to compensate for the speaker impedance variation with frequency. The simulation and test results confirms the validity of the proposed method.

• 한국전기전자재료학회논문지
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• 제28권11호
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• pp.748-751
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• 2015

Sound Masking System technology as by sound the same on all bands and artificially generates a constant sound shield People want to hear or recognize the people with the noise generated from the interior of the way. Prevent hearing or prevent recognition by using the technology to control the audible frequency band Continue to emit constant and uniform shielding sound audible frequency band Even the security content of speech (20 Hz~20 KHz). That interception laser eavesdropping, internal solicitations, during recording Or delay the decoding was a result of the effect of interference calculated Experience noise disturbance index is applied around the Stress Index is the average index is 10.16 was a luxury for the average index is then applied to the index 3.07 Noise is significantly lower stress level has improved noise conditions.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2007년도 한국음성과학회 공동학술대회 발표논문집
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• pp.123-126
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• 2007

This paper suggests a method to improve the performance of the pathological/normal voice classification. The effectiveness of the mel frequency-based filter bank energies using the fisher discriminant ratio (FDR) is analyzed. And mel frequency cepstrum coefficients (MFCCs) and the feature vectors through the linear discriminant analysis (LDA) transformation of the filter bank energies (FBE) are implemented. This paper shows that the FBE LDA-based GMM is more distinct method for the pathological/normal voice classification than the MFCC-based GMM.

• 한국통신학회논문지
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• 제17권6호
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• pp.572-579
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• 1992

마지막으로 Quadrature FM검파기를 사용하여 90$^{\circ}$전이된 신호와 진폭제한된 신호를 합성하여 오디오 신호를 추출하였고 RSSI특성을 측정하였으며 오디오 특성을 기존의 1F모듈과 비교하였다.

• 방송공학회논문지
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• 제26권3호
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• pp.327-330
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• 2021

본 논문에서는 3D 오디오 부호기의 성능 향상을 위해 새로운 잡음 채움 기법을 제안한다. 제안한 잡음 채움 기법에서는 핵심 대역을 IGF 시작 주파수까지가 아니라 MAX_SFB로 설정되는 영역까지로 제한한다. 그리고, IGF 입력 패치의 모든 주파수 영역에 잡음 채움이 수행되도록 한다. 본 논문에서 수정된 잡음 채움 기법의 성능은 MUSHRA 테스트를 통해 평가되었고, 그 결과 기존의 방법보다 우수한 성능을 보임을 입증한다.

• 인터넷정보학회논문지
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• 제18권1호
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• pp.57-64
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• 2017

오늘날 자동차 제조회사들은 차량의 기능과 성능을 향상시키는 기술에 주안을 두는 것은 기본이고, 시장성의 극대화 및 고객 만족도를 높이기 위해 고품질 오디오 장치 구축에도 투자를 아끼지 않고 있다. 특히 고가의 차량일수록 일반 청음실에서 느낄 수 있는 높은 수준의 음향 시설을 갖추려고 한다. 이러한 현상은 차량의 모델에 국한되지 않는다. 요즘 인기가 많은 RV차량에서도 고객들이 수준 높은 음질을 만끽할 수 있도록 제조사들은 고품질의 음향 시스템을 탑재하는 움직임을 발견할 수 있다. 그러나 고품질 음향시스템은 대부분 고가의 부품을 필요로 하는 관계로, 이는 필연적으로 자동차 판매가의 증대를 야기한다. 따라서 비교적 저가의 음향시스템을 이용하더라도 고객이 만족해 할 수 있는 음질을 구현하는 차량 내 음향 시스템 구축의 필요성이 대두되었다. 즉, 인간의 청각적 특성이 고려된 객관적인 자동차 '오디오 시스템 성능 측정 지표' 및 튜닝 방법에 관한 연구가 필요하다. 본 논문에서는 RV차량의 오디오 시스템의 성능을 평가하고 개선하기 위해 인간의 청각적 특성이 고려된 오디오 신호의 특성을 사물인터넷(IoT) 센서를 이용해 측정하고 분석하였다. 분석 결과 사람에게 민감한 대역의 높은 에너지지가 있는 점은 인지에 대한 비중을 높일 수 있으나, 해당 대역만 강조된 경우에는 성가심을 유발할 수 있는 것으로 나타났다. 그리고 왜곡된 주파수 평탄도는 음질에 나쁜 영향을 줄 수 있어 주파수 응답의 평탄화를 필요로 한다는 점을 발견할 수 있었다.

• 대한임베디드공학회논문지
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• 제2권1호
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• pp.31-42
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• 2007

A transform coding scheme for the transmission of audio data in ZigBee based wireless personal area networks (WPAN) is presented in this paper. Here, wavelet transform is exploited to encode the features of audio data included mainly in the low frequency region. As a result, it is confirmed that the presented scheme recovers the original audio signals much accurately while it transmits the binary data compressed as 37.5% of the entire data generated without coding scheme. Especially, the mean-squared error between the recovered and original audio data approaches $10^{-4}$ when the signal-to-noise power ratio is sufficiently high. Hence, the presented coding scheme which exploits the wavelet transform is possibly applied for high-quality audio data transmission services in a small-scale sensor network based on ZigBee. Such a result is considered to be applicable as a basic material to update the technical specifications and develop the applications of ZigBee in WPANs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권2호
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• pp.522-539
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• 2021

In order to solve the problems of the existing audio fingerprint method when extracting audio fingerprints from long speech segments, such as too large fingerprint dimension, poor robustness, and low retrieval accuracy and efficiency, a robust audio fingerprint retrieval method based on feature dimension reduction and feature combination is proposed. Firstly, the Mel-frequency cepstral coefficient (MFCC) and linear prediction cepstrum coefficient (LPCC) of the original speech are extracted respectively, and the MFCC feature matrix and LPCC feature matrix are combined. Secondly, the feature dimension reduction method based on information entropy is used for column dimension reduction, and the feature matrix after dimension reduction is used for row dimension reduction based on energy feature dimension reduction method. Finally, the audio fingerprint is constructed by using the feature combination matrix after dimension reduction. When speech's user retrieval, the normalized Hamming distance algorithm is used for matching retrieval. Experiment results show that the proposed method has smaller audio fingerprint dimension and better robustness for long speech segments, and has higher retrieval efficiency while maintaining a higher recall rate and precision rate.

• 한국컴퓨터정보학회논문지
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• 제20권8호
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• pp.7-13
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• 2015

Recently, there are serviced user customized advertisement of various type using smart device. Representative services are advertisement service using light of smart TV screen or audible sound of smart TV to transmit advertisement information. However, those services have to do a specific action of smart device user for advertisement information or need audible audio information of TV contents. To overcome those weakness, therefore, we propose an advertisement method using inaudible sound of speaker based on smart device. This method supports the transfer of advertising content to the smart device user with no additional action or TV audio signal required to access that content. The proposed method used two high frequencies among 18kHz ~ 22kHz of audible frequency range which smart TV can send out. And it generates those frequencies synthesized with audio of TV contents as trigger signal which can send advertisements to smart device. Next, smart device analysis the trigger signal and request advertisement contents related to the signal to server. After then, smart device can show the downloaded contents to user. Because the proposed method uses the high frequencies of sound signals via the inner speaker of the smart device, its main advantage is that it does not affect the audio signal of TV content. To evaluate the efficacy of the proposed method, we developed an application to implement it and subsequently carried out an advertisement transmission experiment. The success rate of the transmission experiment was approximately 97%. Based on this result, we believe the proposed method will be a useful technique in introducing a customized user advertising service.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.187-192
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• 2010

In this paper, intrusion detection technique based on the sound field variation of audio frequency in the security space is proposed. The sound field formed by sound source can be detected with the microphone when the obstacle or intruder is positioned. The sound field variation due to the intruder is based on the interference of audio wave. With the help of numerical simulation of sound field formations, the increase or decrease of sound pressure level is analyzed not only the obstacle, but also the intruder. Even the microphone is positioned behind the source, sound pressure level can be increase or decrease due to the interference. Frequency response test is performed with Gaussian white noise signal to get the whole frequency response from 0 to half of sampling frequency. There are three security cases. Case 1 is the situation of empty space with and without intruder, case 2 is the situation of blocking obstacle with and without intruder, and case 3 is the situation of side blocking obstacle with and without intruder. At each case, the frequency response is obtained first at the security space without intruder, and second with intruder. From the experiment, intruder size of $50cm{\times}50cm$ can be successfully detected with the proposed technique. Moreover, the case 2 or case 3 bring about bigger sound field variation. It means that the proposed technique have the potential of more credible security sensing in real situation.