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.
23. Suppose that, under the conditions given in Figure 3, sound waves travel a distance of 1 km from a source to a detector. Based on Figure 3, the least energy would be absorbed from the sound waves by the seawater if it has which of the following salinities?
Your Answer is
Correct Answer is A
Explanation
As can be seen from Figure 3, the smaller the salinity, the smaller the sound absorption. So choose the smallest salinity.