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.

25. As the acidity o f seawater increases, sound absorption decreases. Based on Figure 2, at a depth of 0.05 km, a salinity of 35 ppt, a frequency of 10 kHz, a water tem­perature of 20°C, and a pH of 6.0, is the sound absorp­tion less than 0.75 dB/km or greater than 0.75 dB/km?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

The pH originally given in Figure 2 is 8.0, but the pH was changed to 6.0 in the title. According to the sound absorption given in the question stem, it will decrease with the increase of salinity, then the decrease of pH means the increase of acidity, so the sound absorption should decrease.