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.
22. Based on Figure 1, the sound absorption at a frequency of 18 kHz is about how many times as great as the sound absorption at a frequency of 12 kHz?
Your Answer is
Correct Answer is H
Explanation
Looking at Figure 1, when the abscissa is 18, the ordinate is about 2.0, and when the abscissa is 12, the ordinate is about 1.0, so 2 times should be selected.