• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.877-878
• /
• 2009

To realize the flexible audible display (FAD), polymer dispersed liquid crystal(PDLC) is deposited on PVDF(Poly-vinylidene fluoride) film with piezoelectric property. With applied audio signal, it makes sound more than 70 dB in 700 Hz-10kHz. In case of transparency it is opaque and transmittance is less than 10% at 550nm wavelength without bias voltage. It is turned to be transparent and show transmittance of 66% with driving voltage of 60V.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.153-159
• /
• 1996

The acoustic characteristics of a direct radiator type loudspeaker has been studied in this paper. The vibration displacement of the speaker cone paper obtained by the finite element analysis has been converted into the vibration velocity and used as a boundary condition for the acoustic analysis. The frequency characteristics and the sound pressure distribution of the loudspeaker resulted from the radiation of the cone vibration have been calculated by the boundary element analysis. The numerical results have been verified by experiments carried out in an anechoic chamber. The variations of the acoustic characteristics due to the changes of some design parameters have been examined using the numerical model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.469-474
• /
• 2005

The most recent trend on digital hearing aid is to increase the ratio of signal to noise by directivity or to develop noise reduction algorithm inside DSP IC chip. This paper designed, fabricated and tested a digital hearing aid directivity testing device in which a micro-mouse-1ike the stepping motor with a speaker rotates around an examinant. Both ears of the examinant were fixed with ITE hearing aids in order to response to receiving sound. The experimental results were compared with a boundary element method program for verification. The diameter of the directivity testing device was 2 [m] and the micro-mouse was precisely controlled by PICBASIC micro processor.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2019.05a
• /
• pp.577-578
• /
• 2019

지향성 스피커는 초음파를 이용하여 소리에 직진성을 부여하여 특정 방향으로만 소리를 전달할 수 있다. 이러한 지향성 스피커는 초음파의 직진성 때문에 소리를 청취함에 있어 일반 스피커와 달리 전달감이 풍부하지 못하다는 단점이 있다. 본 논문에서는 청취자에게 음원이 전달되는 과정을 모델링한 머리전달함수를 사용한다. 지향성 스피커를 통하여 방사되는 음원에 머리전달함수를 전처리하여 전달감을 개선한다.

• Phonetics and Speech Sciences
• /
• v.11 no.1
• /
• pp.19-27
• /
• 2019

Lateral approximants are well known as having complex articulatory characteristics, which vary cross-linguistically, across speakers, and across utterances. However, less attention has been paid to the articulation of Korean laterals, which do not contrast with a rhotic and may thus exhibit greater-than-normal variability. The focus of this study is to investigate the general articulatory characteristics of the Korean lateral [l] as well as the articulatory variation using novel 3D ultrasound imaging methods. The results of this study revealed significant between-speaker variation and some vowel-dependent variation with regard to the articulation of the Korean lateral [l], which has not been reported previously. Even though all participants in this study showed an anterior occlusion, the place of articulation and the size of the occlusion varied greatly across speakers. The data also revealed that left-right asymmetry is present in the articulation of the Korean lateral. The individual variation of the Korean lateral [l] suggests that it has a large articulatory-acoustic space for variation, since it has no contrasting sound that causes perceptual confusion.

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.4
• /
• pp.207-214
• /
• 2011

Human auditory acuity decreases naturally due to aging. But recently cases of impaired hearing at a young age are increasing greatly. The biggest reason for such an increase of population with impaired hearing is popularization of various kinds of portable multimedia appliances. Many studies on impaired hearing due to noises caused by the earphone and headphone are being made, but there are few studies on noise-impaired hearing caused directly by mobile phone communication. Based on a precedent inquiry, this study proposes a technique for preventing noise-impaired hearing applying to an active noise reduction technique onto bone conduction speaker. This technique is a method for reducing noises by antiphase oscillation through bone conduction speaker with ambient noises. If the proposed system is applied, the noise level that is actually introduced to audition decreases by more than 12 dB, and such a decreased amount of sound volume fundamentally prevents the factors of noise-caused hearing difficulty due to mobile phone communication. Sensibility test results showed that adequate communication was possible even in such a situation where communication volume was decreased like this.

• MALSORI
• /
• no.38
• /
• pp.41-70
• /
• 1999

Researches on perception have, in recent years, been increasingly popular as a means of accounting for cross-linguistic sound patterns (Ohala, 1992; Hemming, 1995; Jun, 1995; Steriade, 1997 among others). In loanword phonology, Silverman(1990, 1992) argues that words from a source language are scanned through the perceptual level and that the features perceived by a speaker are stored in the input to be processed according to his/her native language's phonological constraints. The purpose of this paper is to test the validity of Silverman's proposal by examining the correlation between perception and production of Korean learners of English. We specifically focussed on perception and production of stop release by contrasting English loanwords with English words loarned through education to see if there were any significant differences. The results showed that there was no substantive correlation between the Korean speakers' perception of the loanwords pronounced by English speakers and their own production of those words. In the case of English words, however, the Korean speakers' production was closely related with their perception, although some inter-speaker variations were observed. With Optimality Theory (Prince & Smolenksy, 1993) as a theoretical framework of analysis, it was shown that the theory is a useful means of implementing a phonetics-phonology interface and relating perceptual processes with speech production. Specifically, under the assumption that loanwords with [t]~[t/sup h/] alternation (e.g.,'cut') are originally borrowed into Korean as two different input forms, all the alternations could be straightforwardly accounted for in terms of a unified ranking of constraints.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.6
• /
• pp.251-257
• /
• 2014

An actuator system is a type of motor designed to control a mechanism operated by a source of energy, in the form of an electric current by converting energy into some kind of motion. As audio actuators, transforming electric voltage signal into audio signal, speakers and amplifiers are commonly used. In applications of industry, high output power systems are required. For these systems to generate high-quality output, it is essential to control output impedance of audio systems. We have developed an adaptable power supply for driving active amplifier systems with variable loads. Depending on the changing values of resistance of the speaker which produces audible sound by transforming electric voltage signal, the power supply source of the active amplifier can generate the maximum power delivered to the speaker by an adaptable change of loads. The amplifier is well protected from the abrupt increment of peak current and an excess of current flow.

• The Journal of the Acoustical Society of Korea
• /
• v.24 no.3
• /
• pp.150-159
• /
• 2005

This paper addresses a voice personality transformation algorithm which makes one person's voices sound as if another person's voices. In the proposed method, one person's voices are represented by LPC cepstrum, pitch period and speaking rate, the appropriate transformation rules for each Parameter are constructed. The Gaussian Mixture Model (GMM) is used to model one speaker's LPC cepstrums and conditional probability is used to model the relationship between two speaker's LPC cepstrums. To obtain the parameters representing each probabilistic model. a Maximum Likelihood (ML) estimation method is employed. The transformed LPC cepstrums are obtained by using a Minimum Mean Square Error (MMSE) criterion. Pitch period and speaking rate are used as the parameters for prosody transformation, which is implemented by using the ratio of the average values. The proposed method reveals the superior performance to the previous VQ-based method in subjective measures including average cepstrum distance reduction ratio and likelihood increasing ratio. In subjective test. we obtained almost the same correct identification ratio as the previous method and we also confirmed that high qualify transformed speech is obtained, which is due to the smoothly evolving spectral contours over time.

• Journal of the Korean Society of Radiology
• /
• v.12 no.3
• /
• pp.335-341
• /
• 2018

With the improvement of medical state, patients' expectations for the most advanced medical equipment are increasing. Particularly, Magnetic Resonance Image (MRI) is used as one of the core image diagnosis methods in all clinical area. However, it has been reported that many of patients who go through the examination suffer from anxiety to the severe noise level during the examination. In this study, both the noise reduction evaluation of headsets with sound-blocking materials added to existing sound-absorbing materials and the existence of sound blocking materials as artifacts on the examination image are tested. An MRI test noise is recorded as a speaker by cross-ordination the sound material (sponge) and the sound material (acrylic plate, copper plate, and 3D copper plate) inside the headset made from 3D pring. A quantitative assessment of headsets showed that the average headset value was 81.8 dB. The average dB value of the most soundproof material combination(Copper, acrylic plate, sponge, sponge) headsets on headsets with added charactering material was measured at 70.4 dB, and MRI showed that the copper was diamagnetic substance and excluded. The second most soundproof headset(Sponge, acrylic plate, 3D copper plate, sponge) was measured at 70.6 dB and MRI showed no artifacts. The same simulation of the material printed with a 3D copper PLA containing approximately 40 % copper powder resulted in no artifacts, therefore, the material output as a 3D printing was better suited for use. For MRI related research, the mutual development of 3D printing is highly anticipated.