• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.247-253
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• 2021

Directional ultrasonic speakers that are used to hear sound only in a specific area have been continuously researched on various improvements in terms of sound quality and cost compared to general speakers. In this paper, we propose a DSP based hybrid-type ultrasonic speaker that can be heard at the same time as a general speaker in order to compensate for the sound in the low-band range, considering that it is difficult to hear the low-band sound below 500 Hz due to the sensor characteristics of the ultrasonic speaker. In the case of the system that is implemented by simply connecting a general speaker and an ultrasonic speaker, there are issues of high cost and difficulties of control as two amplifiers are used to playback ultrasonic and general sound sources. In addition, sound quality deteriorates due to the difference in playback time between ultrasonic and general sound sources. In order to improve issues of cost, control and sound quality, we developed hybrid-type ultrasonic speaker with a DSP based amplifier that can simultaneously playback by synchronizing the general sound source with the regenerated ultrasonic sound source, in addition to implement the existing CODEC functions such as Dynamic Range Control (DRC) and Equalizer (EQ).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.383-390
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• 2018

Piezoelectric micro-machined ultrasonic transducers for highly directional speaker need DC bias voltage. Most existing power amplifiers are not suitable for use in highly directional transducers because they are based on AC. In addition, since the piezoelectric micro-machined ultrasonic transducer has a large capacitive reactance, the power efficiency of the power amplifier is very low. Thus this paper proposes a new high efficiency power amplifier with DC bias voltage. In addition, by designing a matching circuit to compensate the capacitive reactance of the micro-machined ultrasonic transducer, the power efficiency of the power amplifier increases. The operating characteristics of the proposed power amplifier was verified by an experimental prototype. The proposed power amplifier is expected to be widely used in designing and implementing other related power amplifiers.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.5
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• pp.83-94
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• 2016

Providing a voice alarm to drivers approaching a work zone could be an effective alternative to mitigate the potential safety problems of the work zone. This study conceived a voice alarm with a direction sound speaker and a field test was conducted that evaluated the feasibility of the voice alarm at a highway work zone. During the field study, we carried out on-site driver surveys to obtain drivers' perception and preference, collected approaching speeds, and measured sound level during the off-peak 2-hour for two days, respectively. The results showed that while the voice alarm has the potential to be an effective tool in improving safety, the alternative appeared to have the negative effect of noise. Further refinement to a voice alarm with a directional speaker is required to improve feasibility, and the results are expected to be utilized as basic data useful for the refinement.

• The Journal of the Acoustical Society of Korea
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• v.42 no.5
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• pp.388-394
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• 2023

When the vibration of the thin panel by exciting single point is used to radiate sound, the inherent vibration characteristic of the plate itself causes influence on the radiated sound. A conventional panel speaker system usually uses the single or double point excitations for generating the sound through the panel itself. The radiated sound can be easily distorted due to the modal characteristics of the plate so it is difficult to expect sufficient sound power or high radiation efficiency. In this paper, to achieve an immersive sound field, the multiple speaker zones on a thin panel are created with the limited number of actuators. The designated vibration field which can generates directional sound is realized by employing the vibro-acoustic inverse rendering methods. Actuators are arranged from the positions which have the advantage of implementing with multi-modal excitations. The location and number of actuators are compared with the location and number of controllable speaker zones by conducting numerical simulations.

• Journal of the Korea Society of Computer and Information
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• v.28 no.12
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• pp.97-104
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• 2023

In this paper, we propose a harmful bird repellent system using directional speakers. Existing sound systems for the extermination of harmful birds have the disadvantage of reducing effectiveness due to the learning effect of birds due to problems caused by noise pollution and monotonous sounds. In this paper, directional speakers are used to minimize surrounding noise. In addition, the up-down and left-right angles of the speaker driving device were freely adjusted to maximize usability. Additionally, the problem of performance degradation due to learning effects was solved by using various scanning patterns. In the future, we plan to develop a platform capable of central control by applying remote control functions and a deep learning model that can recognize bird species.

• International journal of advanced smart convergence
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• v.5 no.4
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• pp.21-25
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• 2016

Recent development in multi-channel surround is emerging in various formats to provide better stereoscopic and sound effects to consumers in recent broadcasting. The ability sound localize the sound sources in space is most considerable design factor on multi-channel surround system for human earing perception model. However, this paper propose the change of the sound localization according to the spacing of the speakers, which is not covered in the existing research focus on sound system design. Presently the sound system uses the position and number of the speakers to localize the sound. In the multi-channel surround environment, the proposed design uses the sound localization is caused by the directional characteristics of the speaker, the distance between the speakers and the distance between the listener and the speaker according to the directivity is required. The proposed design is simulated using virtual measurement with MATLAB simulation environment and performances are measured.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.30-36
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• 2013

Recently the globalization of the media content industry, various activities have been made in the field of art and the speaker system is very important in the sound industry which is one of the arts. The directional characteristics of a loudspeaker refer to the radiation of sound in certain directions and are among the most important features of a loudspeaker. Designing a loudspeaker that can keep all of its constant directivity at all frequencies is difficult due to the wavelengths of audio frequencies and the size of horns and transducers. This study proposed gradient array methods to improve low frequency pattern control of full-range speakers to maximize Direct to Reverberant Ratios at the listeners.

• The Journal of the Acoustical Society of Korea
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• v.30 no.8
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• pp.468-473
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• 2011

Speech may not be clearly understandable in the room that is highly reverberant, due to the loss of consonants intelligibility. Therefore, it is very important to obtain a high sound pressure level of direct sound in reverberant room. A properly designed sound reinforcement system can not provide the good speech intelligibility without the absorption treatments of walls. With using the highly directional speaker, we can transmit the sound energy into only the areas where people are sitting. This can be help to improve the speech intelligibility. In this paper, even in reverberant rooms, it will be shown that the good speech intelligibility can be obtained by only the directivity control of speaker without the room treatment. Also, it would be more improved by the properly room tuning using an equalizer.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.411-414
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• 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-like 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 diameter of the directivity testing device was 2 [m] and the micro-mouse was precisely controlled by PICBASIC micro processor.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.81-84
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• 2004

In this paper, we propose a virtual sound localization algorithm which improves the sound localization accuracy and sound color preservation for two channel and multi-channel surround speaker layouts. In conventional CPP laws, the sound direction is different from the panning angle and the sound color is different from real sound source especially when the speakers are spread out widely. To overcome this drawback, we design a virtual sound localization algorithm using directional psychoacoustic criteria (DPC) and sound color compensator (SCC). The analysis results show that in the case of the proposed system, the sound direction is the same as the panning angle in the audible frequency range and the sound color is less deviated from a real sound source than the conventional CPP law. In addition, its performance is verified by means of subjective tests using a real sound source.