Acoustical Science and Technology
Online ISSN : 1347-5177
Print ISSN : 1346-3969
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Volume 28 , Issue 1
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PAPERS
  • Hideo Suzuki
    Volume 28 (2007) Issue 1 Pages 1-6
    Released: January 01, 2007
    JOURNALS FREE ACCESS
    Whether the piano touch can affect the piano tone quality or not has been a subject of discussion for more than 70 years. Many studies have been conducted on this subject, but most of the conclusions so far were on the negative side. This is possibly because the effect of the touch on physical and tone quality differences are so small and, therefore, very careful recording and analysis are needed to find the subtle differences. This paper describes results of spectrum analysis of hard and soft touch tones, which were recorded with a maximum attention on the equality of sound levels of tones to be compared. Recording and analysis of notes G3, G4, and G5 showed that the touch can affect the spectrum of sound only for G5 in a very small degree, which might become invisible without careful graphical comparisons. The listening tests conducted using recorded sounds showed that not all but some people can discriminate the differences of tone quality between the hard and sort touches. The result of this study is very important since it showed, for the first time, that the touch can produce physical and psychological differences of piano tones even though in a much lesser degree than most pianists expect.
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  • Tomonao Okubo, Kohei Yamamoto
    Volume 28 (2007) Issue 1 Pages 7-15
    Released: January 01, 2007
    JOURNALS FREE ACCESS
    In this paper, we describe a method for predicting sound propagation behind barriers with an acoustical device mounted on their top edge to reduce the diffracted sound. The sound-reduction efficiency of the edge-modified noise barrier was investigated previously with a sound source and a receiver located along a circular arc around the barrier top. It was reported that the efficiency is determined as a function of the angles of the source and the receiver, and that it is independent of their radii. On the basis of this finding, a procedure of predicting the diffracted sound field behind an edge-modified noise barrier is proposed in this paper. The prediction of sound propagation is simply modeled by the sum of multiple paths, which idealize interference due to ground reflection, and the angle-dependent efficiency of the edge device is applied to each path. The efficiencies of absorptive and pressure-release devices are determined by scale-model experiments, and the results are substituted into the prediction model. In comparison with the two-dimensional boundary element analyses, it is shown that the proposed procedure predicts the diffracted sound field precisely, including both the interference by ground reflection and the effect of the edge device.
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  • Hisaharu Suzuki, Akira Omoto, Kyoji Fujiwara
    Volume 28 (2007) Issue 1 Pages 16-26
    Released: January 01, 2007
    JOURNALS FREE ACCESS
    In this paper, we propose a simple method that considers boundary conditions in a finite difference time domain (FDTD) scheme by varying density, sound speed and flow resistance. A method based on a Rayleigh model is also proposed, and by these methods, we can design the frequency characteristics of normal incident absorption coefficient arbitrarily. These methods have three advantages: 1. easy coding, 2. easy designing of a frequency characteristic of normal incident absorption coefficient and 3. easy configuration of material thickness. For example, by our method, we can simulate the sound field in a reverberation chamber with a thick material such as glass wool. To confirm the accuracy of the model used, we compare the normal incident absorption coefficient with a one-dimensional exact solution. Results show that the model is sufficiently accurate. Although our method requires a high cost for calculation power and memory, a practical increase in elapsed time can be ignored. This method provides an easy way of analyzing the inner region of a material.
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TECHNICAL REPORTS
  • Tomoyasu Taguti
    Volume 28 (2007) Issue 1 Pages 27-32
    Released: January 01, 2007
    JOURNALS FREE ACCESS
    A method to control the velocity of piano tones of MIDI tone synthesizers on the basis of equal loundness property is presented. The idea is a parameterization of equal loudness contour of velocity with a physical correlate to the loudness. A listening experiment was conducted to get the equal loudness contours on a particular sound synthesizer with the method of adjustment, where the standard stimulus was note C4 and the comparison stimuli were notes n in the chromatic scale C2 ∼ C7. A new unit velo was introduced to identify these contours so that a velo whose value is V refers to the loudness of a note that sounds equally loud as C4 sounded at velocity V. Regarding the physical correlate to the loudness, the single event sound exposure level (LAE) was chosen to fix the method. By relating the LAE-value, l, of C4 to the equal loudness contour, a mapping formula from (n,l) to velocity v, i.e., g:(n,l) |→v=g(n,l), was established. By this mapping, note n played at velocity g(n,l) produces a tone whose loudness is equal to the tone of C4 sounded at l dB in the sense of LAE; a unit name dyn was given to l to refer to this loudness.
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  • Yukiko Nota, Tatsuya Kitamura, Kiyoshi Honda, Hironori Takemoto, Hiroy ...
    Volume 28 (2007) Issue 1 Pages 33-38
    Released: January 01, 2007
    JOURNALS FREE ACCESS
    Magnetic resonance imaging (MRI) provides an excellent noninvasive method for imaging of the human body, though it presents a critical problem of loud machine noise during scanning which prevents the subjects from being able to listen to auditory stimuli. In this report, we describe a method of auditory stimulus presentation in an MRI system in which a bone-conduction speaker system is used to reduce exposure to airborne noise while maintaining effective auditory stimulation. The results indicate that this method guarantees high-quality MRI structural data during vowel production in phonation-synchronized MRI scans. The method is also shown to be beneficial for functional MRI (fMRI) experiments: activation patterns were equivalent to those of conventional air-conduction systems with less noise exposure.
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