In this study, we investigated the effects of a previous sound on loudness by performing paired comparison experiments. Two pure tones measuring 74 to 86 dB SPL at 500 Hz were presented monaurally at a certain interstimulus interval (ISI), which was set between 0.5 and 8 s. One of the pure tones was presented in one ear, and then the other was presented in the contralateral or ipsilateral ear. The subject compared the loudness of two pure tones and responded which sound was felt louder. The effect of presentation order in the paired comparison was calculated from the experimental results, and then the previous sound effect was obtained from the presentation order effect. As results, the sound presented second in the ipsilateral ear was perceived to be about 1 dB softer than the first sound at an ISI of 0.5 s even when both sounds had the same SPL. On the contrary, the second sound in the contralateral ear was perceived to be about 1 dB louder than the first sound significantly. This effect is referred to as ''auditory reinforcement.'' The effect level of auditory reinforcement decreased as ISI increased.
In the present study, we investigated the effect of a previous sound on loudness at the absolute threshold of hearing. The change in the absolute threshold of hearing was measured when a pure tone preceded the test tone for the measurement of the threshold. The previous sound at 60 dB SPL was presented first in one ear, followed by the presentation of the test tone in either the contralateral or ipsilateral ear after an interval of 0.5 s. Both the previous and test sounds had the same frequency, 500 Hz, and the same duration, 3 s. The change in threshold was obtained from the difference between the thresholds with and without the previous sound. As a result, the threshold was found to decrease significantly by approximately 2 dB when the previous sound was presented in the contralateral ear. On the other hand, the threshold was only slightly changed when the previous sound was presented in the ipsilateral ear.
The effects of tone curve and display size on Kansei evaluation of High Dynamic Range (HDR) images were investigated with Japanese and Chinese observers. Forty HDR images (5 tone curves x 4 sizes x 2 contents) were evaluated for Kansei impression using a semantic differential (SD) method with 16 Japanese and 16 Chinese observers with normal color vision. For each adjective, the evaluation value was plotted against the average lightness of the tone curve, and the resulting curves were divided into five types: monotonic increase (MI), monotonic decrease (MD), peak in the upper portion (PU), peak in the lower portion (PL), and flat (F). The results revealed size dependency in evaluations of "Easy to view" and "Difficult to view", which are PU and PL type adjectives, respectively. Size dependency was less prominent in the evaluations of adjectives categorized as MI, MD, and F types, suggesting that the influence of size is related to the effects of the tone curve. A factor analysis examining the evaluation data for both groups of observers extracted three factors for Japanese and two factors for Chinese observers. These results suggest that Kansei evaluation is more multilateral in Japanese observers than in Chinese observers.
In this study, we attempted to evaluate airconditioning sounds in a vehicle from the viewpoint of sound quality. First, we carried out an experiment to select suitable words for evaluating airconditioning sounds in the compartment of a vehicle. The subjects of the experiment selected several words that were appropriate to represent images of the airconditioning sounds from a list of adjectives. As a result of a cluster analysis of the experimental data, the seven evaluation words ''quiet,'' ''refreshing,'' ''heavy,'' ''wide,'' ''muddy,'' ''violent,'' and ''dry'' were selected as the evaluation words. Next, we carried out a subjective evaluation experiment by the rating scale method. The subjects of the experiment evaluated each presented sound in seven degrees for the seven evaluation words. As a result of a factor analysis, the airconditioning sounds were found to be represented by three factors: ''rough,'' ''space,'' and ''refreshing.'' Finally, we carried out an experiment to evaluate the airconditioning sounds using psychoacoustic parameters such as loudness and sharpness. As a result, we found that the rough factor correlated with loudness and space and refreshing factors correlated with sharpness.
This paper describes the interstimulus interval dependence of the loudness difference limen obtained by taking into account the presentation order effect of sound stimuli. A paired comparison experiment of pure-tone sounds was carried out at different interstimulus intervals, and the experimental data were analyzed, taking into account the presentation order effect. The following two characteristic effects were obtained. First, the difference limen changed depending on the interstimulus interval. A logarithmic relation was found between the difference limen and the interstimulus interval. The difference limen was about 0.6 to 1.6 dB at an interval of 0.5 to 64 s. Second, the order effect also changed depending on the interstimulus interval. The sound presented first was perceived as being louder than the sound presented second at an interval of 0.5 to 4 s, and the sound presented second was perceived as being louder than the sound presented first at an interval of 16 to 64 s, although the sounds were of the same sound pressure level. When the interval was 8 s, the sound presented first was perceived as being as loud as the sound presented second. Based on the above findings, we estimated the region where the difference in loudness could not be detected. The obtained results show that the region is not symmetrical for the upper and lower boundary levels. BACKGROUNDSubjective evaluation tests of loudness are frequently performed not only in psychoacoustics studies but also in various product development tests. However, if the accuracy of a subjective evaluation test is low, the reliability of the data will be compromised, and the results will be inaccurate. It is, therefore, very important that evaluation tests be carried out accurately. To do that, we must find a suitable method and environment. It is widely recognized that the constant method [1][2][3][4], in which sound stimuli are presented randomly and there is a minimal load on the subjects, is one of the most accurate methods. The constant method is used for paired comparisons and it has two important restrictions: do not change any parameters except for the evaluation target, and do not spend a lot of time for the comparison interval to do not forget the first sound. However, changing the target parameters for a very complex or big evaluation target is still a very timeconsuming process. In this situation, we need to know how long the subject can retain information about the sound presented in the experiment, and how accurately subjects can detect changes in the sound.A number of studies on the loudness difference limen have been carried out. For example, Riesz (1928) undertook basic research on the difference limen by using modulation noises [5]. Miller (1947) investigated the difference limen for white noises [6]. Jesteadt (1977) showed the frequency and loudness dependence of the difference limen for pure tones [7]. Clement et al. (1999) studied the relationship between the difference limen and the interstimulus interval [8]. However, few eva...
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