ATOC Transmission

ATOC Transmission Sounds


ATOC HX-554 acoustic source (75 Hz) on the DSVSS Laney Chouest ready for deployment off Kauai during July, 1997. The acoustic source is a large ceramic cylinder mounted on a frame. Electrical current passed through the cylinder will cause it to expand and contract, creating the 75Hz sound waves for the ATOC project. Photo Credit: Scripps Institution of Oceanography.

Acoustic tomography uses the travel time of sound in the ocean to measure the temperature of the ocean over large areas. The ATOC (Acoustic Thermometry of Ocean Climate) project measures temperatures in the North Pacific Ocean with acoustic tomography.The sound source used in the ATOC project does not make sound all the time. It makes sound for 20 minutes every 4 hours on every fourth day. This results in six 20 minute transmissions for a total of 2 hours every 4 days. The ATOC source used at Hawaii was sending a sound out at a frequency centered on 75Hz with a bandwidth of 35Hz (the sound then has a frequency range of 57-92Hz). The ATOC project used a low frequency because low frequencies travel further in the ocean than high frequencies. The ATOC source is continuing to be used by the North Pacific Acoustic Laboratory (NPAL).