10) A sound wave from a source in the south Atlantic to a receiver in the north Atlantic is shown to travel 7,000 km. If the sound level measured at 100 km from the source is 160 dB re 1Pa, what is the level in north America. Assume the source frequency is less than 100 Hz. Absorbtion in dB/m 10 10 10 10-5 10 10 10 salt water 10* frequency Hz fresh water 10 10 Figure 3.1: The attenuation in dB per m as a function of source frequency for underwater sound propagation. Attenuation is a function of temperature, pressure and salinity. These results are for a temperature of 5 C, and a pressure at 1 atm. Salinity is 35 ppt. For more details see Fisher and Simmons J. Acoust. Soc Am. 62, 558 (1977)