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."

No abstract

No abstract

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.