Passage IV

As sound waves travel through seawater, some of their energy is absorbed by the seawater. This sound absorptiondepends on several factors, including the pH of the water, the depth below the water's surface at which the sound waves travel, the frequency of the sound waves, the water temperature, and the water's salinity (concentration of dis­solved salts in the water). Figures 1, 2, and 3 show一under the given conditions, respectively一how sound absorption (in decibels per kilometer, dB/km) varies with frequency (in kilohertz, kHz), temperature (in °C), and salinity (in parts per thousand, ppt; 1 ppt = 1 g/kg).

Figures adapted from Michael A. Ainslie and James G. McColm, "A Simplified Formula for Viscous and Chemical Absorption in Sea Water." @ 1998 by Acoustical Society of America.

24. Suppose sound absorption by seawater is measured under the conditions given in Figure 2, except that the frequency of the sound waves is 16 kHz. Based on Fig­ures 1 and 2, if the temperature of the seawater is 3°C, will the sound absorption more likely be less than 1.20 dB/km or greater than 1.20 dB/km ?

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

Look at Figure 1 first, and find that the larger the frequency, the larger the sound absorption. So when the frequency in Figure 2 changes from 10 kHz to 16 kHz, the corresponding sound absorption should also be larger.