According to an article in the march 1989 issue of scientific american, seals are believed to have sophisticated acoustic transmission and detection systems that are similar to sonar. for example, mother seals locate their pups by measuring the difference in sound wave arrival times in air and in water. given that the speed of sound w can be related to the isentropic derivative of pressure with respect to density estimate how far a mother seal is from her pup if the time difference between air and water is 3 seconds. air can be assumed ideal with cp = 7/2r. air and water temperatures are about 2 °c. for water under these conditions, the isothermal compressibility κt = 45×10-6 bar-1 and cp ≈ cv