THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

Problems for Chapter 15 441Wilson, O. B., and Leonard, O.B. 1954. Measurements of sound absorption in aqueoussalt solutions by a resonator method. Journal of the Acoustical Society of America 26:223.Wood, A. B. 1941. A Textbook of Sound. New York: Macmillan Company; p. 261.Yeager, E., Fisher, F. H., Miceli, J., and Bressel, R. 1973. Origin of the low-frequencysound absorption in sea water. Journal of the Acoustical Society of America 53: 1705.Problems for Chapter 151. Determine the speed of sound in seawater at 20 m depth and at 20 ◦ C and 34 pptusing the Leroy formula.2. Using the same conditions as in Problem 1, find the speed of sound on thebasis of the Medwin formulation.3. Do Problem 1 using the MacKenzie empirical expression.4. Compare the velocities of sound in seawater at a depth of 5000 ft for thelatitude of 61 ◦ N and the latitude of 19 ◦ N. Convert the depth to meters andspeed of sound to km/s.5. If the sound intensity 1 m from a source is 10 W/m 2 in the sea, find thetransmission loss (TL) and the intensity 50 m from the source due strictlyto spherical spreading. What other factors usually affect the transmissionloss?6. If sound is transmitted in a tube of water, what would be the transmission loss?In real life, would there be transmission loss and why?7. Predict the value of the attenuation coefficient for seawater in which salinityS = 40 ppt, frequency of the signal is 50 kHz, and the temperatureis 18 ◦ C.8. Compare the spherical spreading over r = 100 yards with and withoutabsorption by computing the transmission loss under the conditions ofProblem 7.9. Given a change of seawater sound velocity of 20 m/s for a depth of 150 m,what is the gradient and what would be the radius of curvature in terms of c 0 ?10. If an element of an array has a signal to noise ratio of 40 dB, what would bethe array gain of 25 similar elements in such an array?11. A transducer is rated at a receiving response of –95 dB re 1 V. If an acousticpressure of 3 μPa is applied, what will be the resulting voltage at the terminals?12. A projector is driven with a 1.8 rms ampere current. Its response is rated at120 dB re 1 μPa/A. Find the response in dB.