When Lois Lane asks Mister McTavish to "crush the meteor", she should have called it a meteorite. A meteor is a rock in flight as it enters the atmosphere, once it lands on earths surface it is called a meteorite.
The microphone which is specially tuned to the professors voice is a microphone with a cord. The criminal gang is able, somehow, to leave the professors house with the corded microphone without ever unplugging it. All the while giving instructions to the robot using the microphone.
Only the professor or someone using a special microphone tuned to the frequency of the professor's voice can talk to Mr. McTavish. However when Lois asked the professor where did he find "it" (Mr. McTavish), the comment got the attention of the robot and the professor explains Mr. McTavish is a little sensitive and Lois then refers to the robot by his name. Lois made the comment without using the microphone so Mr. McTavish should not have heard and/or understood it.