• 한국음향학회지
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• 제32권4호
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• pp.329-334
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• 2013

자동차 엔진을 포함한 구동계 및 흡배기계 소음의 특징은 차수 스펙트럼(order spectrum) 분석으로 파악할 수 있다. 기존의 선행 연구에서는 엔진의 1차 및 2차 점화주파수(firing frequency)와 관련된 차수성분이 차실내부 소음에 주요한 영향을 미치는 것으로 알려져 있다. 본 연구에서는 차수스펙트럼의 변환에 따른 차실내부 소음의 음질(쾌적감) 차이를 파악하고자 한다. 이를 위하여 6실린더 및 4실린더 가솔린 엔진을 가진 승용차의 차실 내부 소음을 측정하고, 이 소음에 적응형 디지털 필터(adaptive digital filter)를 적용하여 차수레벨을 가감하는 방법으로 수정한다. 쌍비교법을 이용한 청음실험을 통하여 원음 및 편집음의 음질 정도를 평가하고, 음질 향상을 위한 차수스펙트럼 변화 방향을 제시한다. 결과적으로 반-차수(half-order) 성분의 차수레벨 감소가 차실내부 소음의 쾌적감 향상에 영향을 주는 반면, 점화차수 레벨의 감소가 항상 음질에 긍정적인 영향을 주는 것은 아님을 파악하였다.

• 전기학회논문지
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• 제58권4호
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• pp.857-866
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• 2009

In this paper, a noise cancellation-method using microphone array for digital hearing aids is proposed. The microphone array is located around the ear of a dummy. Speech sound is generated from the forward speaker positioned in the front of the dummy and noise sound is generated from the backward speaker. The speech and noise are mixed in the air space and entered into the microphones. VAD(voice activity detector) and ANC(adaptive noise cancellation) methods were used to eliminate noise in the sound of the microphones. 10 two-syllable words and 4 sentences were used for speech signals. Babble and car interior noise were used for noise signals. The performance of the proposed algorithm was evaluated by SNR(signal-to-noise ratio) and PESQ-MOS(perceptual evaluation of speech quality-mean opinion score). In babble noise condition, SNR was improved as much as $7.963{\pm}1.3620dB\;and\;3.968{\pm}0.6659dB$ for words and sentences respectively. In the case of car interior noise, SNR was improved as $10.512{\pm}2.0665dB\;and\;6.000{\pm}1.7642dB$ for words and sentences respectively. PESQ-MOS of the babble noise was improved as much as $0.1722{\pm}0.0861$ score for words and $0.083{\pm}0.0417$ score for sentences. And PESQ-MOS of the car interior noise was improved as $0.2661{\pm}0.0335$ score and $0.040{\pm}0.0201$ score for words and sentences respectively. It is verified that the proposed algorithm has a good performance in noise cancellation of microphone array for digital hearing aids.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1158-1166
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• 2009

Future luxury car must satisfy the improvement of the luxury sound quality on the vehicle interior noise. Previously, we have analyzed vehicle interior noise by dB(A) based analysis. However, dB(A) has very little to do with the psychological satisfaction of the consumers. People want a sound that is characteristic and refined not a sound that is quiet and common. Subjective test were conducted to determine the relationship between subject' s responses and calculated metric values. People choose the most luxury sound among the various vehicle interior noise. And the purpose of this study is that we understand the metrics which constitute the luxury vehicle sound. We have analyzed vehicle interior noise by using the statistical analysis such as multiple regression method and correlation method. And we organized the index of the luxury sound quality.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1437-1442
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• 2006

The international competition in car markets has continuously required the research about the sound quality of a car. The domestic carmakers have also invested a lot of money for the research and development of interior sound quality of passenger cars. Therefore, the aim of this research is to predict the customer's evaluation of a new vehicle. There are two major research works to achieve this goal in this research. The first one is to search questionnaires about the sound quality, which customers prefer, to identify the relationship between these questionnaires and sound metrics that is a psychoacoustics parameters, and to development sound indexes for the questionnaires. All tests for this work is proceed on the road test during acceleration. The second one is to balance the sound component (engine noise, booming noise, road noise and wind noise) of a passenger. This wok will be tested on the constant speed. All of research results will be contributed to the development of brand sound quality of a new passenger car.

• 소음진동
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• 제1권2호
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• pp.141-147
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• 1991

A vectorial approach is used to reduce the objectionable booming noise in the vehicle interior cabin. After identifying the structural transmisson paths, the structural-acoustic transfer functions are evaluated at those mounting positions. Using the measured deformations in the mounting elements and multiplying them with each dynamic stiffness value one can easily get the dynamic input forces acting on the mounting elements. By summing all the contributors vectorially, most important contributor or transmission path can be determined. According to the experimental information, devised countermeasures are applied to a development car and good results are obtained.

• 한국음향학회지
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• 제21권4호
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• pp.178-178
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• 2002

In this paper, we propose an adaptive wavelet method for car interior noise cancellation. For this purpose, we use a node dependent threshold which minimizes the Bayesian risk. We propose a noise estimation method based on spectral entropy using histogram of intensity and a candidate best basis instead of Donoho's best bases. And we modify the hard threshold function. Experimental results show that the proposed algorithm is more efficient, especially to heavy noisy signal than conventional one.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.283-287
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• 2012

Recently, Most of diverse noise of vehicles has decreased competitively according to development of the automotive manufacturing technology. Especially, Passenger car manufacturers has been conducting buzz, squeak and rattle(BSR) noise test as a method of the noise evaluation tests to reduce an unpleasant sound from interior parts on the driving the car. The purpose of this paper is to confirm the change of the noise generated in the product after the reliability evaluation. Here by the BSR test procedure used the test regulation of 'G' company.

• 한국정보통신학회논문지
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• 제17권7호
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• pp.1571-1576
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• 2013

본 논문에서는 잡음 환경 하에서 음성신호에 대한 신호대잡음비(SNR)를 개선하기 위한 알고리즘을 제안한다. 본 논문에서 제안하는 알고리즘은 백색잡음 및 자동차잡음 등과 같은 배경잡음으로부터 음성신호의 SNR을 개선할 목적으로 먼저 저역, 중역, 고역 SNR 대역에서 SNR을 추정한다. 다음으로 본 알고리즘은 각 대역에서 스펙트럼을 강조함으로써 잡음으로 오염된 음성신호 속에서 잡음신호를 차감한다. 백색잡음, 자동차잡음에 의하여 오염된 음성에 대하여 본 논문에서 제안한 알고리즘이 스펙트럼 차감 방법과 비교하여 양호한 신호대잡음비 값을 구하였다. 실험결과로부터 스펙트럼 차감 방법과 비교하여 백색잡음에 대하여 최대 4.2 dB, 자동차잡음에 대하여 최대 3.7 dB의 출력 신호대잡음비가 개선된 것을 확인할 수 있었다.

• 전기학회논문지
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• 제61권1호
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• pp.179-185
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• 2012

Since the eco-era is getting closer, the importance of noise reducing in the passenger cars of high-speed train is very important. The active noise control is best choice to reduce low frequency noise because the passive one is too heavy for high speed trains where weight is so critical. Also ANC is able to reduce the ambient noise when the environmental-factor changes. To reduce a three-dimensional closed-space sound field like a car of a high-speed rail is hard to do using single channel ANC control system. We used multi-channel FXLMS algorithm which calculation speed is fast and the secondary path estimation is possible in order to take into account the physical delay in electro acoustic hardware control loudspeaker and power amplifier. Firstly, we have measured interior noise of KTX and estimated noise path in KTX test-bed. However there was some problem related to algorithm divergence and increasing the filter order. We have made a simulation of interior environment of KTX car by using three frequency bands of 120Hz, 280Hz, 360Hz as the most important for KTX ANC system. During this research the interior noise reduction of KTX car was made by using the multi-channel FXLMS algorithm. Reduction performance was evaluated and compared each other for open space section and tunnel section. in-situ experiment for the KTX noise reduction by proposed ANC was performed based on data obtained in simulation and they were compared for open space section and tunnel section as well.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.575-577
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• 2009

Traditionally, tire made a role of function, which is supporting vehicle load, making brake, transferring, traction etc. So, there are a lot of studying for the tire. especially, tire noise is one of the most important parameter in the car noise. this thesis shows the method how to reduce the tire noise by using the optimal pitch sequence. Because the optimal pitch sequence prevents tire from generating the pure tone while driving the car on the ground.