What have caused the strange sounds "quackers" is the force of both the professor and the writer.
In the reading, three theories, including orca whale, giant squid and military technology, have
been elaborated. The professor, however, holds the view that all these assumption are incorrect.
First of all, as opposed to the author's idea that "quackers" were made by male and female orca
whales in courtship ritual, the professor states that whale cannot be found inn deep ocean and be
detected by submarines'sonar. In detail, orca whales live in surface of water, while the submarines
are in the deep ocean, so they could not detect the sounds.
What's more, the listening continues to discredit the passage's assertion that giant squid caused
the odd sound, by examining the fact that giant squid cannot appear suddenly and disappeared
several decades later. To be more precise, the giant squids have always lived in deep ocean, but
the Russian submarine first detected the strange sounds in 1960 and they entirely disappeared in
1980s.
Finally, it is the professor's third argument that there is not such advanced technology to develop
fast and silent submarines, which challenges the belief of article that these stray sounds were
from some military technology. Specifically, the submarine cannot change direction so quickly
compared with "quackers" and the noise of submarine's engine did not come along with the odd noise.
An apparent divide exists between the reading and the listening on what caused the odd sounds.