• 한국음향학회지
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• 제31권4호
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• pp.225-234
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• 2012

The anechoic chamber is essential tool to measure the various acoustic parameters with high precision. The chamber provides the climate controlled indoor environments but requires the dedicated room at a great cost in order to isolate and absorb sound field. Provided the purpose of the chamber is specific to the experiments of sound localization, the performance requirements excluding free field can be alleviated for cost effective solution. This paper designs low cost and profile anechoic chamber based on acoustic pyramids and evaluates the performance specified by the Annex of ISO 3745. Data analysis is employed to measure the free and hemi-free field performance over five straight paths for working areas and four paths for non-working areas. The identical two measurement campaigns were conducted for free and hemi-free field chamber which is easily interchangeable by simple labor in this chamber design. In the working area with conventional speaker, the results of these analyses demonstrate that lab-designed anechoic chamber is in conformance with ISO 3745 for 250 Hz - 16 kHz one-third octave band at free field chamber and for 1 kHz - 16 kHz one-third octave band at hemi-free field chamber.

• 한국도로학회논문집
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• 제14권5호
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• pp.201-206
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• 2012

PURPOSES: This study evaluated a measuring technique for tire-pavement interaction noise that uses a noble close proximity (NCPX) method as well as for noise level measured inside of a car (e.g., Inside Noise Level) in term of rumble strips constructed at a tall gate. METHODS: According to the measurements of NCPX and inside noise level (INL), 1/3 octave band frequency analysis and overall noise level calculation were conducted in order to evaluate noise levels of NCPX and INL, depending on types of rumble strips. RESULTS: The tested sections of general concrete pavement surface and two different types of rumble strips were evaluated, using 1/3 octave band frequency analysis and overall noise level. From the analyzed results, it can be concluded that rumble strips generate a relatively huge noise levels when compared to the concrete pavement surface. CONCLUSIONS: Noting that above 3 dBA different noise levels can let drivers know that they are getting close to toll gate; therefore, they should apply their brakes. Thus, the noise levels of rumble strips are required to be reduced, based on considering the neighbors living near toll gates.

• 말소리와 음성과학
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• 제9권4호
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• pp.77-89
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• 2017

This study investigates the phonetic meaning of clarity and turbidity(淸濁) that has been used in psychoacoustics, musicology, and linguistics in both the East and the West. With a view to clarifying the phonetic meaning of clarity and turbidity, this study conducts three perception tests. First, 34 subjects were asked to take one of Clear and Turbid by forced choice for 5 pure and complex tones, respectively, ranging from A2 to A6 differing by octave. Second, they were asked to select between the two choices for 25 pure and complex tones, respectively, ranging from A2 to A4 differing by semitone. Third, they were asked to opt for one of the two choices for 8 different vowels of different formant and fundamental frequencies. Results showed that there is a certain range of tone which is perceived as clear, that clarity level increases as fundamental frequency increases, and that pure tones have a higher level of clarity than complex ones, fundamental frequency being equal. Results also showed that vocal tract resonance enhances clarity level on the whole, and that lower vowels have a higher level of clarity than higher ones. This study is significant in that it demonstrates that clarity level is proportional to fundamental frequency and the first formant frequency, all else being equal.

• 대한전자공학회논문지TC
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• 제38권5호
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• pp.16-22
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• 2001

본 논문에서는 스파이럴 형태의 급전선을 갖는 마이크로스트립 원형 슬롯 안테나를 제안하였다. 이 구조는 편심 스파이럴 안테나를 평면적으로 구현한 것으로서, 주빔이 안테나 평면에 수직한 방향을 향하지 않고 기울어져 있으며 주빔의 방향으로 원형 편파를 갖는다. 또한 주빔의 방향이 주파수 변화에 따라서 ${\theta }$ 와 ${\phi }$ 방향으로 일정하게 변하므로 동작 대역 내에서 주빔의 방향을 예측할 수 있다는 장점이 있다. EM 시뮬레이션을 통하여 설계변수에 따른 안테나의 특성변화를 고찰하였으며 최적의 설계방법을 제시하였다. 최적화 된 구조는 1 octave 이상의 주파수 대역에서 주빔 방향으로 3 dB이하의 축비를 가진다.

• 한국음향학회지
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• 제14권6호
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• pp.32-39
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• 1995

본 연구에서는 음악 신호의 기본주파수 추출에 이용되던 일정 Q 변환에 옥타브 밴드 필터 뱅크를 이용하여 보다 정확한 음악 신호의 기본 주파수를 찾아내고자 한다. 본 연구에서의 방법과 기존의 FFT를 이용한 일정 Q변환에 의한 방법을 동일한 음악 신호에 적용하여 그 결과를 비교한다. 기존의 FFT를 이용한 일정 Q 변환과 동일한 주파수 해상도를 유지하면서도 본 연구에서 제안한 방법의 시간 해상도가 개선되었고, 시간해상도로 인한 처리 음역의 제한을 극복할 수 있었다. 또한 보다 정확한 분석을 위하여 처리 음역과 주파수 해상도를 증진시키고 분석 빈도를 증가시킬수록 본 연구에서 제안한 방법의 연산량이 적어짐을 알 수 있었다.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.55-64
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• 2007

In the built-up structure consisting of a stiff beam and a flexible plate, Grice showed that the plate behaves as an energy absorber in narrow frequency bands(called plate blocking effect). This paper deals with such beam-plate coupled structures, where the plate is an energy absorber and the excited beam is an energy path. It is found that such energy dissipation can occur in the relatively broad bands, if different stiffnesses are used in the rectangular plate. It was experimentally verified by Heckl that the energies in terms of one-third octave band averages transferred to the plate(or dissipated in the plate) increase for increased plate damping. This Paper, however, shows that the energy absorption suddenly reduces at the certain narrow frequency bands where the plate damping effect upon the coupled beam is maximum. Also, in order to minimize energy transfer through the beam in terms of one-third octave band averages, it is advantageous to increase the plate damping closer to the excitation point All these results are based on the wane method.

• Journal of electromagnetic engineering and science
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• 제16권1호
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• pp.44-51
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• 2016

A commercial $0.25{\mu}m$ GaN process is used to implement 6-18 GHz wideband power amplifier (PA) monolithic microwave integrated circuits (MMICs). GaN HEMTs are advantageous for enhancing RF power due to high breakdown voltages. However, the large-signal models provided by the foundry service cannot guarantee model accuracy up to frequencies close to their maximum oscillation frequency ($F_{max}$). Generally, the optimum output load point of a PA varies severely according to frequency, which creates difficulties in generating watt-level output power through the octave bandwidth. This study overcomes these issues by the development of in-house large-signal models that include a thermal model and by applying distributed L-C output load matching to reactive matched amplifiers. The proposed GaN PAs have successfully accomplished output power over 5 W through the octave bandwidth.

• 한국음향학회지
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• 제30권2호
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• pp.100-106
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• 2011

음원의 디지털화가 진행되면서 음악 데이터베이스가 방대해지고 있다. 따라서, 음악 데이터를 보다 효과적으로 관리하기 위해 음악의 특성에 따라 장르별로 자동 분류해주는 시스템이 필요하다. 기존 장르 분류 시스템은 대부분 Mel-Frequency Cepstral Coefficient (MFCC)를 특징 벡터로 이용하고 있다. 본 논문에서는 Auditory Filter Bank를 이용한 Decorrelated Filter Bank (DFB)와 Octave-based Spectral Contrast (OSC)에 texture window를 적용하여 특징을 추출한 후, Support Vector Machine (SVM)을 이용하여 장르 분류를 시도하였다. 기존의 Marsyas 장르 분류 시스템과 비교한 결과 DFB와 OSC로 복합적인 특징 벡터를 구성하면 더 적은 차수의 특징벡터를 사용함에도 4.2 %의 향상된 분류 성공률을 얻을 수 있었다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제12권2호
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• pp.101-107
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• 2012

This study describes a proposed method of converting an input sound signal into a color image by emulating human synesthetic skills which make it possible to associate an sound source with a specific color image. As a first step of sound-to-image conversion, features such as fundamental frequency(F0) and energy are extracted from an input sound source. Then, a musical scale and an octave can be calculated from F0 signals, so that scale, energy and octave can be converted into three elements of HSI model such hue, saturation and intensity, respectively. Finally, a color image with the BMP file format is created as an output of the process of the HSI-to-RGB conversion. We built a basic system on the basis of the proposed method using a standard C-programming. The simulation results revealed that output color images with the BMP file format created from input sound sources have diverse hues corresponding to the change of the F0 signals, where the hue elements have different intensities depending on octaves with the minimum frequency of 20Hz. Furthermore, output images also have various levels of chroma(or saturation) which is directly converted from the energy.

• 한국도로학회논문집
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• 제15권6호
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• pp.61-68
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• 2013

PURPOSES : The purpose of this study is to study the noise reducing effect of Micro Surfacing by comparing general asphalt, longitudinal tining and Slurry Seal. METHODS : This study measures vehicles' noise of each section by the NCPX method that can measure noise between the road surface and the tire at the field. Total sound pressure and sound pressure level by the 1/3 octave band frequency are calculated through the field data of each section. Total sound pressure level is compared by ANOVA test statistically. After ANOVA test, post-hoc test is conducted to know mean difference of surface type by Tukey. RESULTS : As the result of CPB analysis to confirm sound pressure levels by frequency, it was shown that sound pressure levels by frequency are totally similar except for those of frequency bands between 100Hz and 500Hz. The result of ANOVA test and post-hoc test, it was shown that sections of surface type have a difference. The result of Micro Surfacing was lower 2~5dB(A) than other surface type. CONCLUSIONS : It is found that the noise reduction performance of Micro Surfacing was better than other surface type.