- Email: [email protected]
Hypersonic-absorption and sound-speed in water at high pressures
Volume SOA, number 4
PHYSICS LETTERS
16 December 1974
HYPERSONIC-ABSORPTION AND SOUND-SPEED IN WATER AT HIGH PRESSURES~ M. SEDLACEK and A. ASENBAUM Erstes Physikalisches Institut der Universitát Wien, Strudlhofgasse 4, A 1090 Wien, Austria Received 29 October 1974 Speed and attenuation of hypersound (frequency from 5.5 to 6.7 GHz) in water of 25°Chave been measured by Brillouin scattering at pressures ranging up to 1.75 kb. The results of the experiment are in good agreement with ultrasonic data.
Brillouin scattering experiments provide information on the sound propagation properties in liquids at hypersonic frequencies up to a few GHz. For that reason a large number of substances have been investisonic properties gated using this method. of liquidsInformation at elevated pressures on the hyperis however scarce [11. Therefore this paper is intended to presentofsome data on sound speed and at attenuation in water 25°Cbetween lb and 1.75kb frequencies from 5.5 to 6.7GHz. experiment The optical followed arrangement the standard and thedesign, electronics with an of the argon ion laser (single mode, X 0 = 514.5 nm) for the excitation of the spectra [2]. The scattering chamber (built for pressures of up 2.5 kb) was kept at a ternperature of 25±0.1°C.A high precision Bourdon-tube manometer allowed the determination of the pressure
A
This work was supported by the “Fonds zur Forderung der
wissensehaftlichen Forschung” (Projekt Nr. 1893).
/1
Icy
‘I
>10
/~
ZIuJ
1
500
1000
1500
PRESSURE (BARS)
Fig. 2. Pressure dependence of sound velocity in water of 25°C.Vertical bars: hypersonic data. ultrasonic data with error band (interpolated from [3—6]).
with an error of less than 5 b. Assuming that water shows no acoustical relaxation even at high pressures and making use of the fact that it has comparatively small sound damping, the analysis of the spectra of the scattered light is very simple: the frequency shift of the Brillouin peaks, which have their origin in the propagating pressure fluctuations, is given by:
1 0
1< I
~
1
f2vsin(~/2)n/X0 (v: sound velocity,
500 PRESSURE (BARS)
1000
1500
Fig. 1. Pressure dependence of sound damping in water of 25°C.Vertical bars: hypersonic data. : ultrasonic data with error band (interpolated from [3,5]).
(1)
n: refractive index of the liquid,
vacuum wavelength of the laser light, ~: scattering angle.) The full width at half height of the Brillouin peaks follows from the equation
245
Volume 50A, number 4
~f= av/ir,
PHYSICS LETTERS
(2)
(a: coefficient of sound attenuation.) The results of the experiment are shown in figs. I and 2, together with ultrasonic data [3—6J.According to eq. (1) the sound frequency at a fixed scattering angle ~ depends upon v and n, and it therefore extends from 5.5 GHz (1 b) to 6.7 GHz (1.75 kb). For the analysis of the spectrum at 1.75 kb an extrapolated value for n had to be used, since adequate data on the refractive index of water were available only for a maximum pressure of 1.5kb [7, 8]. The error in the velocity was ±0.7%, in the linewidth and hence in a ±15%. The ultrasonic and hypersonic data agree within the limits of error, as can be seen from the figures. The initial assumption, namely, that water exhibits no acoustical relaxation in the investigated range of pres-
246
16 December 1974
sures, has been upheld by the results. However it must be recognized that the errors inherent within the experiment could have masked small effects.
References [11 J.H. Stith, L.M. Peterson, D.H. Rank and TA. Wiggins, J. Acoust. Soc. Am. 55 (1974) 785. [21 M. Sedlacek, Zs. f. Naturforsch. (to be published). [3] 47 5. Hawley, J. Allegra and G. Holton, J. Acoust. Soc. Am. (1970) 137. [4] G. Holton, M.P. Hagelberg, S. Kao and W.H. Johnson, J. Acoust. Soc. Am. 43 (1968) 102. [5] T.A. Litovitz and E.H. Carnevale, J. Appi. Phys. 26 (1955) 816. [6] A.V.J. Martin, J. Rech. C.N.R.S. 41(1957) 251. [7] 68A R.M. (1964) Waxier,489. C.E. Weir and H.W. Schamp, J. Res. NBS. [81J.S. Rosen, 1. Opt. Soc. Am. 37 (1947) 932.
PHYSICS LETTERS
16 December 1974
HYPERSONIC-ABSORPTION AND SOUND-SPEED IN WATER AT HIGH PRESSURES~ M. SEDLACEK and A. ASENBAUM Erstes Physikalisches Institut der Universitát Wien, Strudlhofgasse 4, A 1090 Wien, Austria Received 29 October 1974 Speed and attenuation of hypersound (frequency from 5.5 to 6.7 GHz) in water of 25°Chave been measured by Brillouin scattering at pressures ranging up to 1.75 kb. The results of the experiment are in good agreement with ultrasonic data.
Brillouin scattering experiments provide information on the sound propagation properties in liquids at hypersonic frequencies up to a few GHz. For that reason a large number of substances have been investisonic properties gated using this method. of liquidsInformation at elevated pressures on the hyperis however scarce [11. Therefore this paper is intended to presentofsome data on sound speed and at attenuation in water 25°Cbetween lb and 1.75kb frequencies from 5.5 to 6.7GHz. experiment The optical followed arrangement the standard and thedesign, electronics with an of the argon ion laser (single mode, X 0 = 514.5 nm) for the excitation of the spectra [2]. The scattering chamber (built for pressures of up 2.5 kb) was kept at a ternperature of 25±0.1°C.A high precision Bourdon-tube manometer allowed the determination of the pressure
A
This work was supported by the “Fonds zur Forderung der
wissensehaftlichen Forschung” (Projekt Nr. 1893).
/1
Icy
‘I
>10
/~
ZIuJ
1
500
1000
1500
PRESSURE (BARS)
Fig. 2. Pressure dependence of sound velocity in water of 25°C.Vertical bars: hypersonic data. ultrasonic data with error band (interpolated from [3—6]).
with an error of less than 5 b. Assuming that water shows no acoustical relaxation even at high pressures and making use of the fact that it has comparatively small sound damping, the analysis of the spectra of the scattered light is very simple: the frequency shift of the Brillouin peaks, which have their origin in the propagating pressure fluctuations, is given by:
1 0
1< I
~
1
f2vsin(~/2)n/X0 (v: sound velocity,
500 PRESSURE (BARS)
1000
1500
Fig. 1. Pressure dependence of sound damping in water of 25°C.Vertical bars: hypersonic data. : ultrasonic data with error band (interpolated from [3,5]).
(1)
n: refractive index of the liquid,
vacuum wavelength of the laser light, ~: scattering angle.) The full width at half height of the Brillouin peaks follows from the equation
245
Volume 50A, number 4
~f= av/ir,
PHYSICS LETTERS
(2)
(a: coefficient of sound attenuation.) The results of the experiment are shown in figs. I and 2, together with ultrasonic data [3—6J.According to eq. (1) the sound frequency at a fixed scattering angle ~ depends upon v and n, and it therefore extends from 5.5 GHz (1 b) to 6.7 GHz (1.75 kb). For the analysis of the spectrum at 1.75 kb an extrapolated value for n had to be used, since adequate data on the refractive index of water were available only for a maximum pressure of 1.5kb [7, 8]. The error in the velocity was ±0.7%, in the linewidth and hence in a ±15%. The ultrasonic and hypersonic data agree within the limits of error, as can be seen from the figures. The initial assumption, namely, that water exhibits no acoustical relaxation in the investigated range of pres-
246
16 December 1974
sures, has been upheld by the results. However it must be recognized that the errors inherent within the experiment could have masked small effects.
References [11 J.H. Stith, L.M. Peterson, D.H. Rank and TA. Wiggins, J. Acoust. Soc. Am. 55 (1974) 785. [21 M. Sedlacek, Zs. f. Naturforsch. (to be published). [3] 47 5. Hawley, J. Allegra and G. Holton, J. Acoust. Soc. Am. (1970) 137. [4] G. Holton, M.P. Hagelberg, S. Kao and W.H. Johnson, J. Acoust. Soc. Am. 43 (1968) 102. [5] T.A. Litovitz and E.H. Carnevale, J. Appi. Phys. 26 (1955) 816. [6] A.V.J. Martin, J. Rech. C.N.R.S. 41(1957) 251. [7] 68A R.M. (1964) Waxier,489. C.E. Weir and H.W. Schamp, J. Res. NBS. [81J.S. Rosen, 1. Opt. Soc. Am. 37 (1947) 932.