The goal of the present study is to characterize water sounds that can be used in urban open spaces to mask road traffic noise. Sounds and visual images of a number of water features located in urban open places were obtained and subsequently analyzed in terms of psychoacoustical metrics and acoustical measures. Laboratory experiments were then conducted to investigate which water sound is appropriate for masking urban noise. The experiments consisted of two sessions: (1) Audio-only condition and (2) combined audio-visual condition. Subjective responses to stimuli were rated through the use of preference scores and 15 adjectives. The results of the experiments revealed that preference scores for the urban soundscape were affected by the acoustical characteristics of water sounds and visual images of water features; Sharpness that was used to explain the spectral envelopes of water sounds was proved to be a dominant factor for urban soundscape perception; and preferences regarding the urban soundscape were significantly related to adjectives describing "freshness" and "calmness."

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Psychoacoustical and autocorrelation function (ACF) parameters were employed to describe the temporal fluctuations of refrigerator noise during starting, transition into/from the stationary phase and termination of operation. The temporal fluctuations of refrigerator noise include a click at start-up, followed by a rapid increase in volume, a change of pitch, and termination of the operation. Subjective evaluations of the noise of 24 different refrigerators were conducted in a real living environment. The relationship between objective measures and perceived noisiness was examined by multiple regression analysis. Sound quality indices were developed based on psychoacoustical and ACF parameters. The psychoacoustical parameters found to be important for evaluating noisiness in the stationary phase were loudness and roughness. The relationship between noisiness and ACF parameters shows that sound energy and its fluctuations are important for evaluating noisiness. Also, refrigerator sounds that had a fluctuation of pitch were rated as more annoying. The tolerance level for the starting phase of refrigerator noise was found to be 33 dBA, which is the level where 65% of the participants in the subjective tests were satisfied.

Just Noticeable Differences (JND) in sound quality metrics-Zwicker's loudness, sharpness, roughness and fluctuations strength, and Auto-CorrelationFunction (ACF) parameters-were investigated using refrigerator sounds. An original refrigerator sound was set as a reference stimulus and the reference signal manipulated in terms of sound quality for use as a comparison stimulus. Forty participants were asked to evaluate the differences in sound quality of sound pairs, and the value of JND was determined using the criteria of 75% correct answers. The results showed that JNDs of loudness, sharpness, roughness, and fluctuation strength were 0.5 sone, 0.08 acum, 0.04 asper, and 0.012 vacil, respectively. JNDs of ACF parameters such as ⌽"0…, 1 and 1 were 2.0 dB, 0.4 ms, and 0.08 dB, respectively. The results of the present study provide criteria for sound quality enhancement of refrigerator sounds, especially the amount of value for perceptual improvements. © 2008 Institute of Noise Control Engineering.

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The characteristics of refrigerator noise in an anechoic chamber and in an actual environment were investigated. In order to predict the noise propagation in real apartment house, room acoustic simulations and measurements using different types of refrigerators were conducted. The sound-pressure level of the refrigerator noise in the real living room was much higher than in the anechoic chamber. In addition, an allowable sound-pressure level for refrigerator noise was determined by auditory experiments. For the stimuli of auditory experiments, the dry source of refrigerator noise was presented using a loud speaker at the position of the refrigerator. When the result of the subjective evaluation was at the level 2 (the noise rarely aware but comfortable), in which sound pressure level was about 25 dB(A), 95% of people were satisfied with the refrigerator noise. A semantic differential test using various adjectives was also conducted to evaluate the sound quality of refrigerator noise.

This paper identifies a cause of pick up noise in a laser printer and a relationship between pick up noise and major components related to pick up noise. A pick up sound is affected by many components such as spring force, spring constant, and friction coefficient. Objective evaluation for the pick up sound is difficult because of back ground sound such as operating sound. Especially, a sound between a friction pad and a paper in the process of printing has become an essential issue in an aspect of quality evaluation. However the existing criteria for determining the above sound have solely relied on human's subjective judgments; which highlights the requirement to objectify these criteria. In this paper, the standard of existing pick up noise is established by finding the tonality, which is a psychoacoustic parameter, of noticeable limit sound level. Based on the findings of the method, the study has found factors which cause pick up noise and suggests the substitution of following components of printers such as spring constants, spring force, and the quality of friction pads. As a result, it is confirmed that the proposed pick up noise index has usefulness to classify whether existence of pick up noise with an objective evaluation and not to occur the noise based on design optimized combination of laser printer components.