• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.7
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• pp.112-122
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• 1997

This paper presents active silencing by hysteresis control method and shows its audible noise reduction effect. A Pentium processor and sound blaster 16 card are used for its implementation. The Sound-Blaster 16 executes the A/D, D/A conversion and is used for operating source of lodspeaker for cancelling. As a result, between the frequency range of 100[Hz] and 200[Hz] there is an audible noise reduction effect from 9[dB] to 15[dB], and between the 300[Hz] and 500[Hz] range there is a reduction from 3[dB] to 5[dB].

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.11
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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.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.347-354
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• 2002

In this paper, a comparative study on the performance of two-phase and three-phase randomized pulse position PWM scheme for mitigation of audible switching acoustic noise in motor drives Is done. In the randomized pulse position PWM, each of two-phase or three-phase PWM pulses is located randomly in each switching interval. Simulation and experimental efforts were executed to investigate the spread effects of power spectra of inverter output voltage, waveforms of ripple current and audible switching acoustic noise.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.316-319
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• 1998

RPWM(Random Pulse Width Modulation) is a switching technique to spread the voltage and current harmonics on the wide frequency area. Using randomly changed switching frequency of the inverter, the power spectrum of the electromagnetic acoustic noise cab be spread to the wide-band area. The wide-band noise is much more comfortable and less annoying than the narrow-band one. So RPWM have been attracting an interest as an excellent method for the reduction of acoustic noise on the inverter drive system. In this paper a new RPPWM (Random Position PWM) is proposed and implemented. Each of three pulses is located randomly in each switching interval. Along with the randomization of PWM pulses, the space vector modulation is executed in the C167 microcontroller also. The experimental results show that the voltage and current harmonics were spread to wide band area and that the audible switching noise was reduced by proposed RPPWM method.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.82-89
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• 2002

In this paper, a new two-phase space vector RPWM(Random PWM) is proposed. In the proposed RPWM, each of two-phase PWM pulses is located randomly in each switching interval. Based on the space vector modulation technique, the duty ratio of the pulses is calculated. Along with the randomization of the PWM pulses, we can obtain the effects of spread spectra of inverter output voltage, d.c link current and audible switching acoustic noise as in the case of randomly changed switching frequency. To verify the validity of the proposed two-phase RPWM scheme, the experiment based on the C167 micro-controller was executed. The performance of the proposed scheme was compared with traditional PWM schemes experimentally.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.7
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• pp.21-28
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• 2006

This paper deals with the HVDC system fault analysis and the sound noise analysis. In this paper, the reasons of the audible noise and vibration were analyzed the fault waveform were analyzed using DTR (Digital Transient Recorder). Finally, using the fault current waveform and the vibration equation, the reason of crack of smoothing reactor support is estimated.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.5
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• pp.234-240
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• 2001

Audible noise (AN) produced by corona discharges from high voltage transmission lines is one of the more important considerations in line design. Therefore, line designers must pre-determine the AN using prediction formulas. This paper presents the results of applying evolutionary computation techniques using AN data from lines throughout the world to develop new, highly accurate formulas for predicting a A-weighted AN during heavy rain and stable rain from overhead ac lines. Calculated ANs using these new formulas and existing formulas are compared with measured data.

• Proceedings of the Korea Society of Design Studies Conference
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• 2003.05a
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• pp.10-11
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• 2003

• International Journal of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.70-77
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• 2017

Where there are all the flowers, the songs of all kinds of insects and birds are put in, the sunshine and shadows flicker The forest through which the water sound flows is an optimum resting space. All living creatures in these spaces will awaken the five senses of humans and perhaps turn the sensibility index (EQ). The forest meditation in the forest, which can be an optimal shelter for the people who need it, needs to feel the reverence of nature, to refine emotions, to be a self-reflection, to have a mind to respect, Have an important meaning. In this paper, we tried to consider the cause of the influence of forest sounds on human hearing from the acoustical aspect. The type of sound source of forest was divided into four seasons of spring, summer, autumn, winter. And the change in the duration of the sound during the four seasons, so that the general characteristics of the sounds of the four seasons are as follows: It can be seen that the change in the ratio of sub-band energy is almost equal to the change in dB in frequency of the equal-light curve. To compare this phenomenon, the criterion for changing the sound duration of each forest is natural The main forms of the luminance curve, such as the change in the duration of the white signal in the sound, are determined by the minimum, maximum audible frequency and the most sensitive frequency band, and the auditory characteristics of the other three inflection points Determines the overall shape of the equal-light curve.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.3
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• pp.234-240
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• 2011

In order to obtain the fundamental data about the behavior of sharks by underwater audible sound, this experiment was carried out to investigate the auditory characteristics of tiger shark Scyliorhinus torazame which was caught in the coast of Jeju Island by heart rate conditioning method using pure tones coupled with a delayed electric shock. The audible range of tiger shark extended from 80Hz to 300Hz with a peak sensitivity at 80Hz including less sensitivity at 300Hz. The mean auditory thresholds of tiger shark at the frequencies of 80Hz, 100Hz, 200Hz and 300Hz were 90dB, 103dB, 94dB and 115dB, respectively. The positive response of tiger shark was not evident after the sound projection of over 300Hz. At the results, the sensitive frequency range of tiger shark is narrower than that of fish that has swim bladder. In addition, it is assumed that the most sensitive frequency in auditory thresholds of Chondrichthyes is lower than that of Osteichthyes. Critical ratios of tiger shark measured in the presence of masking noise in the spectrum level range of about 60-70dB (0dB re $1{\mu}Pa/\sqrt{Hz}$) increased from minimum 27dB to maximum 39dB at test frequencies of 80-200Hz. The noise spectrum level at the start of masking was distributed at the range of about 65dB within 80-200Hz.