• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.154-157
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• 2005

Generally, noise from a indoor air conditioner has been measured by overall sound pressure level, dB. Customers evaluation, however, of the noise from an air conditioners should not be depend on the only overall level but also the sensory feeling. Moreover, in this sensory evaluation, irregular, time-varying and uneven sounds which are difficult to describe itself by overall level are more affectable. Unfortunately however the formal evaluation method for this kinds of noise is not determined yet. In this research, the evaluation method for tonal noise, which is one of the unmeasurable sounds by overall level, is proposed to evaluate its acceptability based on the consumer's sense of hearing. To consider the consumer's sense, several times of Jury evaluation are carried out. The proposed approach could be applied to the other sound, which acoustical characteristics are similar to the tonal noise .

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.599-607
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• 2006

The ship radiated noise appear the various characteristic signals due to the mechanic system in the ship, the propeller and the interaction between ship body and sea water. Generally, it is classified two main components: the speed dependent signal and the speed independent signal. It is required that very complex procedure to classify the signal origin from the ship-radiated noise. This paper presents techniques to automatically detect and classify the tonal signals ken the ship-radiated noise, using the Q factor and the neural network.

• Journal of KSNVE
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• v.8 no.6
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• pp.1037-1042
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• 1998

This paper discusses the dependence of the convergence rate on the acoustic error path in these popular algorithms and introduces new algorithms which increase the convergence region regardless of the time-delay in the acoustic error path. We also Propose a novel control algorithm (AFC/CAFC) for tonal noise cancellation. The proposed algorithm estimates the magnitude and phase of the tonal noise. The algorithm uses the steepest descent method for the phase/magnitude estimation. Performances of tile CAFC algorithm are presented in comparison with those by the AFC algorithm based on computer simulations and experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.1047-1054
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• 2000

A numerical simulation was made to delineate the re-distribution of tonal noise generated from the equally-spaced blade passing frequency (BPF). A pressure-wave model was employed to analyze the tonal noise. An optimal solution for diversifying the tonal peak noise was obtained by rearranging the unequally-spaced blade angles. This was based on the fact that the noise energy is transferred from BPF to the neighboring frequency band. A limit condition for the minimum blade angle spacing was imposed. The unbalancing problem was also considered to avoid the weight bias.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1123-1129
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• 2003

The noise of maneuvering submarines or vessels can be divided into the tonal signals and broadband ambient noise. Tonal signals are from the revolution of motors and engines of vessels, and broadband ambient noise is from the bubbles which are generated by the propellers and the flow of water around vessels. We can analyze the kinds and the speed of vessels if we analyze the tonal signals and ambient noise. But, it is difficult to divide the tonal signals form the ambient noise when the power of tonal signal is much weaker than the power of ambient noise. In this paper, we detect the direction of arrival(DOA) of the noises generated by vessels with the automatic tracking window(ATW) preprocessing algorithm, and make a beam to the direction of the targets. We suggest a method which can separate weak tonal signals from broadband ambient noise with the ATW algorithm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.3
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• pp.286-293
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• 2003

The unsteady flow characteristics and associated blade tonal noise of a cross-flow fan are predicted by computational methods. The incompressible Navier-Stokes equations are time-accurately solved for obtaining the pressure fluctuations between the rotating blades and the stabilizer. and the sound pressure is predicted using Curie's equation. The discrete noise characteristics of three impellers with a uniform and two random pitch (type-A and -B) blades are compared by their SPL (Sound Pressure Level) spectra. and the frequency modulation characteristics of the BPF (Blade Passing Frequency) noise are discussed. Besides. a mathematical model is proposed for the prediction of discrete blade tonal noise and is validated with available experimental data. The fan performance is also compared with experimental data. indicating that the random pitch effect does not significantly alter the performance characteristics at ${\phi}$ 〉 0.4

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.155-162
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• 2009

Because the tonal sound of the underwater noise in a naval vessel can be identified from the sub-marine of the enemy, it should be reduced sufficiently. This kind of the noise usually comes from the structure-borne noise of the onboard machine and transfers to the sea through the hull of the ship. The vibration at the high frequency can be reduced sufficiently with damping material. In this paper, the damping coefficient of the steel plate with damping sheet is evaluated by experiment. Using these evaluated properties, the numerical analysis is performed in order to evaluate how much vibration of the generator can be reduced applying damping sheet on the encloser and base of it.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1329-1337
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• 2009

Because the tonal sound of the underwater noise in a naval vessel can be identified from the sub-marine of the enemy, it should be reduced sufficiently. This kind of the noise usually comes from the structure-borne noise of the onboard machine and transfers to the sea through the hull of the ship. The vibration at the high frequency can be reduced sufficiently with damping material. In this paper, the damping coefficient of the steel plate with damping sheet is evaluated by experiment. Using these evaluated properties, the numerical analysis is performed in order to evaluate how much vibration of the generator can be reduced applying damping sheet on the encloser and base of it.

• Journal of the Korean Society of Visualization
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• v.21 no.3
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• pp.39-48
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• 2023

In this study, we investigate the effects of slots installed on the tip of a rotor blade on aerodynamic characteristics. The slots weaken the strength and spatial coherence of the tip vortex at early vortex age and accelerate the dissipation of the generated tip vortex. Accordingly, the turbulence intensity of the rotor wake is reduced at both near and far wake, which leads to a reduction in broadband noise. Tonal noise is also reduced by mitigation of tip vortices, but tonal noise reduction is limited to a narrower range of azimuths than broadband noise due to the extinction of tip vortices. In addition, slots reduce both mean thrust and thrust fluctuations. Reduction in thrust fluctuations leads to a reduction in blade loading noise, resulting in a reduction in tonal noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.116-121
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• 2013

Panaroma Sun roof's sun shade motor elicits two major sounds when operating: the tonal sound and the white noises. Generally, the sound related to the sharpness contributes the most to the quality of motors' tonal sound. The primary purpose of this study was to set the loudness of the motor's objective tonal sound utilizing the masking effect by its white noises. To conduct this study, the sound made by the operating sun shade motor was categorized into two different subsets of masker and test tone to examine the masking threshold. Also, the shifts of masking threshold were observed with the varying masker loudness.