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May 1983

Volume 73, Issue S1, pp. S1-S106

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back to top Session X.Physical Acoustics IV: Absorption‐Relaxation
Contributed Papers
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Sound absorption in aqueous mixtures of MgSO4‐HCl and MgSO4‐H2SO4 (A)

F. H. Fisher

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S49-S49 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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An analysis is made of the Kurtze and Tamm acoustic absorption data in MgSO4‐HCl and MgSO4‐H2SO4 aqueous mixtures. The reduction in absorption as acid is added to a 0.05 MgSO4 solution cannot be explained on the basis of ion‐pairing alone. However, these apparently different sets of data for each acid‐MgSO4 mixture can be analyzed on a common basis. The results are explained empirically in terms of normal mode kinetic coupling of volume changes between the MgSO4 and HSO4− dissociation reactions as a function of free hydrogen ion concentration.
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Irreversible thermodynamics formulation of multiple relaxation processes, with application to laser‐generated sound in 4 °C water (A)

Allan D. Pierce

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S50-S50 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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An irreversible thermodynamics formulation for a fluid with an arbitrary number of internal coordinates leads to an inhomogeneous wave equation for acoustic pressure with source term, −(β/cp) ∂q/∂t − (K/cp)∂2q/∂t2. Here β is coefficient of thermal expansion, q is heat added per unit time and volume, and K is a constant of the order of 10−11 s/°C which is related to the relaxation time matrix. The theory explains the tripolar pressure pulses observed by Hunter et al. [J. Acoust. Soc. Am. 69, 1563–1567 (1981)] following irradiation of 4 °C water (for which β = 0) by short laser pulses. A precise evaluation of K follows from analysis of reported waveforms. If water has only a single relaxation process, the magnitude of K is at variance, however, with the Hall structural relaxation theory of bulk viscosity, for which the estimated relaxation time is of the order of 10−12 s. The conflict is resolved if water has a second relaxation process that has negligible influence on absorption and wave speed, but which substantially influences β. The relaxation time for this newly inferred process may be as long as 10−6 s. [Work supported by ONR.]
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Molecular energy transfer measurements with a pulsed spectrophone (A)

Henry E. Bass and Hai‐Xing Yan

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S50-S50 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Taking CO2 and CO2/N2 mixtures as examples, the pulsed spectrophone has been used to investigate vibrational relaxation processes in gases. The electromagnetic excitation of the CO2(001) mode gives rapid cooling of the gas measured as a decrease in pressure followed by heating as the energy supplied by the laser pulse is transferred to translation. The gas then gradually returns to equilibrium due to spontaneous radiation and thermal conduction. By comparing measured pressure waveforms with theoretical simulation, information can be obtained about the energy transfer processes taking place. The vibrational relaxation times compare favorably to those measured using laser induced fluorescence and ultrasonic absorption techniques. The primary advantage of the pulsed spectrophone is its ability to measure multiple relaxation times and determine relaxation mechanisms. [Work partially supported by the Office of Naval Research.]
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The measurement of sound propagation from an elevated source (A)

R. Raspet, P. D. Schomer, and S. D. Hottman

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S50-S50 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Accurate source characterization and sideline decay prediction is necessary for assessing the environmental impact of rotary wing aircraft. Analysis of aircraft flyby sound level data indicates that atmospheric refraction can have a significant effect on the measured sound levels at longer slant distances [R. Raspet, J. Acoust. Soc. Am. Suppl. 1 70, S68 (1981)]. We have begun a measurement program to investigate the effect of atmospheric refraction on the sound levels from an elevated source for a variety of meteorological conditions. In this paper we will describe the physical layout of our experimental range, the experimental design, and instrumentation used. Prime consideration in the design are (1) simultaneous sound level and meteorological measurements; (2) reduction of wind noise so that measurements can be performed under all wind conditions; (3) sufficient sampling of the sound field at each distance so that the level measured represents an average level received in the region of the ground.
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Sound propagation studies in dilute model dispersion in the low‐frequency range (A)

M. A. Barrett Gültepe, M. E. Gültepe, and E. B. Yeager

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S50-S50 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Acoustic absorption measurements using a spherical resonator in the range. 10 to 300 kHz were made in 0.126% by wt polystyrene latex dispersions in an aqueous medium. The particles were synethesized and carefully cleaned and purified after preparation in order to obtain well characterized surfaces. After cleaning and purification, the particle surfaces exhibit mainly sulfonate end groups with hydrogen counterions. The excess absorption measured over and above that attributable to viscous drag and heat conduction losses considerably exceeds that from an aqueous solution of styrene sulfonic acid of comparable molarity, measured with the same technique, and further, differs in frequency dependence. [Work supported by ONR.]
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Pressure dependence of sound absorption in an aqueous solution of CaSO4 (A)

C. C. Hsu and F. H. Fisher

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S50-S50 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Sound absorption has been measured in a 0.011M aqueous solution of CaSO4 at 25 °C. The values of maximum absorption per wavelength, (αλ)max × 106, are 10.3 ± 0.1 at 1 atm and 7.7 ± 0.1 at 307 atm. The relaxation frequency is 177 ± 9 kHz at 1 atm and, within experimental error, is independent of pressure. This corresponds to an inner coordination sphere substitution rate of about 106, two orders below that of 2 × 108 quoted by Eigen and Tamm. At 1 atm, the CaSO4 absorption is about 30% that of the same concentration of MgSO4.
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Effect of pressure on sound absorption in seawater and in aqueous solutions of MgSO4 (A)

C. C. Hsu and F. H. Fisher

J. Acoust. Soc. Am. Volume 73, Issue S1, pp. S50-S50 (1983); (1 page)

Online Publication Date: 12 Aug 2005

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Measurements have been made at 25 °C of the effect of pressure on sound absorption in Lyman and Fleming synthetic seawater from 30–300 kHz up to 307 atm. Similar measurements were made in 0.02M MgSO4 solution and in a 0.02M MgSO4‐0.6M NaCl solution. The decrease with pressure of absorption per wavelenght (αλ) in seawater differs substantially from those reported by other investigators. The relaxation frequency, within experimental error, was found to be independent of pressure. For seawater, increasing pressure to 307 atm reduced absorption by 26.3%, very nearly the same (28.2%) as was observed previously for 0.5M MgSO4 solutions. The addition of 0.6M NaCl to the 0.02M MgSO4 solution decreased the absorption by a factor of 4 and the effect of pressure was found to be independent of the NaCl concentration. The Eigen and Tamm multistate dissociation parameters which best describe the pressure dependence of sound absorption and electrical conductance in a 0.02M MgSO4 solution predict a 21.4% decrease in absorption at 307 atm compared to the observed 19.6% decrease. However, these parameters yield an equilibrium constant which differs from conductance derived value by a factor of 3.
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