A method for determining the length and cross-sectional area of the vocal tract from target formants is presented. The area function was approximated by summing several mode functions to reduce the number of degrees of freedom among the area parameters. Furthermore, the tract length was represented as a function of the coefficients for two principal modes. The estimation was made based on the perturbation relationship, i.e., a sensitivity function was used to represent the change in formant frequency due to a small perturbation of the vocal-tract shape. Starting from initial values, the vocal-tract parameters were optimized iteratively, and the sensitivity functions were used as linear constraints to update the parameter values. The estimation accuracy was examined using area function data for 10 English vowels (Story and Titze, J. Phon., 26, 223–260, 1998). The results showed that the method is capable of determining vocal-tract shape with a satisfactory degree of accuracy, though the estimation accuracy strongly depends on the type of vowel. The dependency of the estimation error on the initial values of the parameters was also investigated.
This study is aimed at investigating how room acoustics affect the timbral brightness of clarinet tones. For semi-anechoic stimuli, nine natural clarinet tones produced at three different dynamic levels and three different notes were used. Reverberant stimuli were generated by convolving each semi-anechoic tone with two different binaural room impulse responses. The stimuli were presented dichotically over headphones to the fifteen participants at equal loudness. The scale values of timbral brightness for each stimulus at equal notes were obtained through Scheffe's paired-comparison test. The results showed that timbral brightness was significantly varied depending on room acoustic conditions. The results also showed that the spectral centroid of tones produced at equal dynamic levels and equal notes was varied depending on room acoustic conditions. The variation range was equivalent to 48–52% of the overall range of that caused by varying both room acoustic conditions and dynamic levels at each note. Timbral brightness was found to linearly increase with the increase in the spectral centroid, irrespective of room acoustics. The slope of timbral brightness corresponding to the spectral centroid was about 1.5–1.6 times steeper for the reverberant tones than for the semi-anechoic tones.
In Japan, drivers frequently use their vehicle horn as a signal in various situations such as when passing each other. Furthermore, pedestrians are honked at by drivers. Such horn use may create noise problem for people nearby. Therefore, a questionnaire survey was carried out to ascertain the current circumstance of vehicle horn use in Kanto and Kansai of Japan, while a similar survey was previously carried out in Fukuoka. Respondents were asked about the latest or last-remembered case of horn use in various situations of being drivers and pedestrians. With regard to an experience of being honked at by another driver, the questionnaire included questions relating to the aim of horn use, the timing pattern of the horn, and the respondent's psychological reaction. The results revealed that drivers' brief and frequent vehicle horn use to express gratitude or gain another's attention in various places from narrow lanes to main roads was similar among the three surveyed areas including Fukuoka. Long honks and horn use to gain another's attention or to alert another to danger remarkably aroused negative psychological reactions in pedestrians. No significant difference in the manner of the driver's horn use was found among the three surveyed areas.