In this paper, we propose a sound-database system, which is able to extract stored data using sound as a key for the query. This ability realizes the sound extraction without having to specify the acoustical characteristics of the sound. The system repetitively searches and presents sounds, which have similarity in timbre to the key sound, until the user finds a satisfactory sample. The parameters that characterize a sound’s timbre, which is a psychoacoustical factor for sound perception, are adopted as the sound’s indices in the database and used for similarity matching in the searching process. Because the definition of similarity in sounds differs from user to user, the proposed system is equipped with an adaptive preference-weighted searching mechanism that adapts its searching focus based on the user’s preference. Because of the ability of the proposed system to realize an intuitive query, this system can be broadly used by a user without special acoustical knowledge.
In automatic voice response systems where a large number of words are inserted into fixed sentences, such as in voice-guided car navigation systems, one of the most important problems is the adjustment of the fundamental frequency (F0) contour of the inserted word to suit the F0 context of the fixed sentence. In Mandarin Chinese, it is required that the effects of tone and intonation on F0 contours be represented separately. We proposed a scheme to solve the problem in terms of a word-level F0 range (WF0R) and a set of relative F0 change fields. WF0R in any position of a sentence is a tone-independent general F0 range to represent the intonational effect; whereas F0 change field (F0CF) is an F0 range that accounts for the result of both the tone combination of words and the intonation. Relative F0CF is regulated in reference to WF0R and represents tonal effect on F0. In this paper, we statistically examine the invariance of the relative F0CF with various speakers’ speech data. From an analysis of four native speakers’ utterances of 160 disyllabic words in the initial, middle and final parts of three carrier sentences, which were recorded on 2 or 3 days, it is found that: (1) Chinese speakers read words in the same sentence position with stable relative F0CFs, even on different days; and (2) the relative F0CFs in the middle position of a sentence are generally the same as those in the initial position but slightly different from those in the final position.
This paper describes a method to estimate the position of a crack in a concrete block using several vibration pick-ups. An array of vibration pick-ups is attached on the concrete block, and a vibration pulse is forced by using a small hammer. If there is a crack, a reflection wave is generated from the position of the crack. Therefore, conventional methods to estimate the position of vibration source seems to be useful for this purpose. However, since the concrete block is elastic, there are three wave propagation modes; the surface wave mode, the primary wave mode and the secondary wave mode. Since the necessary primary wave mode is not significant in magnitude, we cannot estimate the position by the conventional methods. To increase the S/N, we had already proposed a method to eliminate the first-coming surface wave. However, the method was insufficient to achieve a higher S/N. Therefore, this paper proposes a new method to achieve a better location of a crack. Some experiments were carried out, and good results were obtained.
A new method of feedback control of sound fields that minimizes the total acoustic energy in a sound field of any shape excited by an unknown disturbance is presented. The proposed method is based on the finite element method and H∞ control theory, and achieves both robust performance and high stability. The structure of the acoustic plant is formulated such that the H∞ norm of the system transfer function expresses the total acoustic energy in the sound field. Computer simulations verify that the damping of a sound field can be increased without leading to instabilities of the closed loop system. It is also verified that the resonant peaks in the frequency spectrum of the total acoustic energy can be attenuated in the low-frequency range involved in the nominal model of the plant without exciting the residual mode dynamics in the high-frequency range. The control performance can be tuned by adjusting the weighting factor. Using this method, it is possible to dynamically alter the characteristics of a sound field.
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