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Technical Briefs

A Study on the Sound Quality Evaluation Model of Mechanical Air-Cleaners

[+] Author and Article Information
Jeong-Guon Ih1

Department of Mechanical Engineering, Center for Noise and Vibration Control (NoViC), KAIST, Daejeon 305-701, Koreaj.g.ih@kaist.ac.kr

Su-Won Jang

Department of Mechanical Engineering, Center for Noise and Vibration Control (NoViC), KAIST, Daejeon 305-701, Korea

Cheol-Ho Jeong2

Department of Mechanical Engineering, Center for Noise and Vibration Control (NoViC), KAIST, Daejeon 305-701, Korea

Youn-Young Jeung

Tech. Center, Woongjin Coway Co., Ltd., Seoul 151-818, Korea

1

Corresponding author.

2

Present address: Department of Electrical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.

J. Vib. Acoust 131(3), 034502 (Apr 21, 2009) (5 pages) doi:10.1115/1.3085889 History: Received January 20, 2008; Revised October 23, 2008; Published April 21, 2009

In operating the air-cleaner for a long time, people in a quiet enclosed space expect low sound at low operational levels for a routine cleaning of air. However, in the condition of high operational levels of the cleaner, a powerful yet nonannoying sound is desired, which is connected to a feeling of an immediate cleaning of pollutants. In this context, it is important to evaluate and design the air-cleaner noise to satisfy such contradictory expectations from the customers. In this study, a model for evaluating the sound quality of air-cleaners of mechanical type was developed based on objective and subjective analyses. Sound signals from various air-cleaners were recorded and they were edited by increasing or decreasing the loudness at three wide specific-loudness bands: 20–400 Hz (0–3.8 barks), 400–1250 Hz (3.8–10 barks), and 1.25–12.5 kHz bands (10–22.8 barks). Subjective tests using the edited sounds were conducted by the semantic differential method (SDM) and the method of successive intervals (MSI). SDM tests for seven adjective pairs were conducted to find the relation between subjective feeling and frequency bands. Two major feelings, performance and annoyance, were factored out from the principal component analysis. We found that the performance feeling was related to both low and high frequency bands, whereas the annoyance feeling was related to high frequency bands. MSI tests using the seven scales were conducted to derive the sound quality index to express the severity of each perceptive descriptor. Annoyance and performance indices of air-cleaners were modeled from the subjective responses of the juries and the measured sound quality metrics: loudness, sharpness, roughness, and fluctuation strength. The multiple regression method was employed to generate sound quality evaluation models. Using the developed indices, sound quality of the measured data was evaluated and compared with the subjective data. The difference between predicted and tested scores was less than 0.5 points.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

A-weighted noise spectrum (SPL) measured in the frontal direction for varying operation levels. The curve with the lowest level depicts the background noise in the anechoic chamber.

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Figure 2

A-weighted sound power level (PWL) of an air-cleaner varying the operation level: (—◀—) background noise, (—◼—) level 1, (—●—) level 2, (—▲—) level 3, (—▼—) level 4, and (—◆—) level 5

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Figure 3

Measured sound intensity distribution in the 1/3-octave band: (a) 200 Hz band and (b) 630 Hz band

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Figure 4

Calculated SQ metrics: (a) N, (b) S, (c) R, and (d) F

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Figure 5

Factor scores by the PCA: (◼) sound 1, (▲) sound 2, (◆) sound 3, and (●) sound 4. Two factors are classified: performance and annoyance feelings. Each factor was in seven scales: −3 to +3.

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Figure 6

Subjective response for the second experiment. (a) Annoyance and (b) performance. (●) All juries and (◼) consistent juries.

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Figure 7

A comparison of tested and predicted subjective scores: (a) performance and (b) annoyance

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Figure 8

Spectra of several modified sounds: (—◼—) sound 1 (original), (—●—) sound 2 (+LF, −MF, −HF; ΔL=6 dB), (—▲—) sound 3 (+LF, +MF, −HF; ΔL=4 dB), and (—▼—) sound 4 (+LF, −HF; ΔL=6 dB)

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