• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.818-821
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• 2005

The sound measurement procedures of IEC 61400-11 are applied to field test and evaluation of noise emission from 1.5 MW wind turbine generator (WTG) at Yongdang and 660 kW WTG at Hangwon in Jeju Island. Apparent sound power level, wind speed dependence and third-octave band levels are evaluated for both of WTGs. 1.5 MW WTG at Yongdang is found to emit lower sound power than 660 kW one at Hangwon, which seems to be due to lower rotating speed of the rotor of WTG at Yongdang. Equivalent continuous sound pressure levels (ECSPL) of 660 kW WTG at Hangwon vary more widely with wind speed than those of 1.5 MW WTG at Yongdang. The reason for this is believed to be the fixed blade rotating speed of WTG at Yongdang. One-third octave band analysis of the measured data show that the band components around 400-500 Hz are dominant for 1.5 MW WTG at Yongdang and those around 1K Hz are dominant for 660 kW WTG at Hangwon.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.20-28
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• 1989

SEA(Statistical Energy Analysis) method has been applied to predict the sound radiation power from vibrating machinery. In this study, sound radiation power was predicted from coupled structures by transmission of vibration, which composed of two plates welded into an L shape. The predicted sound radiation power is in agreement within 2 or 3 dB on octave band comparing with values obtained from direct measurements. Also, in order to prove the validity of this method in changes of sound radiation power associated with modifications to structures, rubber pad was stuck on a plate. The results agree approximately within 3 or 5 dB. And SEA method is valuable for the optimal design to reduce the noise. Additionally, this paper suggests that the logarithmic decrement method is valid as the one for finding the loss factor.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.9
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• pp.820-825
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• 2004

In this paper an octave tuning voltage controlled oscillator which is used in set-top TV tuner was designed. Oscillation frequency range is 0.9 GHz～2.2 GHz with 1.3 GHz bandwidth. By using 4 varactor diodes in base and emitter of transistor, wide-band tuning, sweep linearity and low phase noise could be achieved. Designed VCO requires a tuning voltage of 0 V ～ 20 V and DC consumption of 10 V and 15 mA. Designed VCO exhibits an output power of 5.3 dBm $\pm$1.1 dB and a phase noise below -94.8 dBc/Hz ＠ 10 kHz over the entire frequency range. The sweep linearity shows 65 MHz/V with a deviation of $\pm$10 MHz.