In the reading,the author presents some theories about the cause of the odd sounds. However,the professor in the lecture points out some problems in all his assertions.
Firstly,even though the passage suggests that the strange norses were actually the calls of male and female orca whales during a courtship ritual,the professor argues that the submarines in deep water cannot detect the calls of them. Because Orca whales always live near the surface of the ocean,the submarines which are deep in the sea may not easily detect the sound emitted by orca whales.
Moreover,despite the statement in the passage that the sounds were caused by giant squid,the professor contends that such explanation is not reasonable. Since the sounds started in the 1960s and disappeared after 1980s while giant squid always live,if we attribute the sound to giant squid,we cannot explain why they stop making such sounds after 1980s. In other words,the sound may not give out by giant squid.
Finally,the author asserts that the Russian submarines were picking up stray sounds from some military technology and they were using a kind of technology designed to avoid being detected by sonar. Nevertheless,the professor proves that it's not a reliable explanation,since even by the technology nowadays,a submarine cannot change direction so fast and keep silent.