Sound Waves in Rooms

SUMMARYThis paper analyzes the properties of sound field transfer functions that change with the sound source distance (SSD), by measuring reverberant room impulse responses from a point of view of the phase characteristics. We analyzed the propagation phase (PP) according to the SSD in a reverberant field that R. Lyon investigated, by using a narrow-band linear regression analysis of the impulse responses and considered the relation to the zero distribution of the transfer function. As a result, we clarified that the SSD information is included in the phase frequency characteristics of the minimum-phase component and the variances from the PP. The distance from the source where the PP could be observed corresponds to the coherent field based on the wave theory or the critical distance defined by the energy ratio of direct to reverberation sound. Therefore, the field where the PP could be observed in the minimumphase component of the transfer function can be treated as the direct sound field. In addition, we also present that the reverberation phase (RP) separated and extracted along with PP from the phase frequency characteristics is according to the estimated value from the number of non-minimum-phase zeros.

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“…6. A coherent field as described by Morse and Bolt [3,4] r ph is plotted in Fig. 6 as a broken line.…”

Section: Direct Sound Field Estimationmentioning

confidence: 99%

“…Furthermore, we estimate the direct sound field in a reverberant sound field based on changes from PP to RP according to the SSD, and compared to the estimated value of the direct sound field based on the wave theory [3,4], and of the critical distance defined from the energy ratio of direct sound to reverberant sound [5].…”

Section: Introductionmentioning

confidence: 99%

Phase response of transfer functions and coherent field in a reverberation room

Takahashi

Tohyama

Yamasaki

2006

Electron Comm Jpn Pt III

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“…With the acoustic impeadance known, we can know the sound wave-absorbing properties of materials under any conditions [1,2] and estimate the absorption characteristics of a sample composed of several elements by calculating the acoustic impeadance [3] of those elements.…”

Section: Introductionmentioning

confidence: 99%

Absorption of Sound Wave by Fabrics

Aso¹,

Kinoshita²

1963

Journal of the Textile Machinery Society of Japan

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The acoustic impeadance density of fabrics has been measured by the tube method with the following results:1) The acoustic reactance shows the negative value at low frequencies and the positive value at high frequencies. 2) If the rear air space of the fabric is deep, the acoustic reactance is zero at low frequency.3) The reactance of a pliable fabric having only a limited number of interlacing points is zero at high frequency. 4) A stiff fabric having many interacting points shows a large value of resistance. 5) The value of resistance of a fabric is nearly constant if the depth of its rear air space is kept in a range of 6 to 10 cm. 6) The value of resistance of a pliable fabric is constant, irrespective frequency.The value of resistance of a stiff fabric increases with an increase in frequency. The relation between the acoustic impeadance density and the sound absorption coefficient has been studied with the following results:(1) Irrespective of the mechanism of sound wave absorption, the absorption coefficient of a fabric which has a rear air space is calculable by Pariss' formula.(2) The impeadance density of a fabric of the viscosity resistance type is calculable by Paris' formula and its normal incident absorption coefficient is calculable without complicated figuring.

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“…Morse and Bolt [2] first introduced the normal modes theory into room acoustics, and developed a non-linear transcendental characteristic equation through combining the assumed sound pressure modes with complex impedance boundary conditions on the walls. Maa [3] derived the transcendental equation for a rectangular room with non-uniform acoustical boundaries which took the same form as that of a uniform acoustic admittance case, while the impedance term was consequently non-uniform on certain wall.…”

Section: Introductionmentioning

confidence: 99%

Acoustic Analysis of Enclosed Sound Space as well as Its Coupling with Flexible Boundary Structure

Du¹,

Liu²,

Liu³

2018

Computational and Experimental Studies of Acoustic Waves

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Combustion instability is often encountered in various power systems, a good understanding on the sound field in acoustic cavity as well as its coupling with boundary flexible structure will be of great help for the reliability design of such combustion system. An improved Fourier series method is presented for the acoustic/vibro-acoustic modelling of acoustic cavity as well as the panel-cavity coupling system. The structuralacoustic coupling system is described in a unified pattern using the energy principle. With the aim to construct the admissible functions sufficiently smooth for the enclosed sound space as well as the flexible boundary structure, the boundary-smoothed auxiliary functions are introduced to the standard multi-dimensional Fourier series. All the unknown coefficients and higher order variables are determined in conjunction with Rayleigh-Ritz procedure and differential operation term by term. Numerical examples are then presented to show the correctness and effectiveness of the current model. The model is verified through the comparison with those from analytic solution and other approaches. Based on the model established, the influence of boundary conditions on the acoustic and/or vibro-acoustic characteristics of the structural-acoustic coupling system is addressed and investigated.

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Sound Waves in Rooms

Cited by 180 publications

References 98 publications

Phase response of transfer functions and coherent field in a reverberation room

Phase response of transfer functions and coherent field in a reverberation room

Absorption of Sound Wave by Fabrics

Acoustic Analysis of Enclosed Sound Space as well as Its Coupling with Flexible Boundary Structure

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