It was likely a cost-cutting measure by the producers - to produce the sound effect might have cost a lot of extra money.
It could also be explained that the Visitors, in the year between when they were first driven from Earth by the human race, might have developed a way to disguise their voices or invented a new device that hides the characteristic reverberation they used to have.
A year after Liberation Day, courtesy of the red-dust bacteria, the humanoid, lizard-like aliens develop a resistance to the micro-organism and try to regain control of the Earth--only now, some humans are knowingly working with them.
Who are the characters in V?
Charles, Chris Farber, Diana, Dr. Julie Parrish, Elias Taylor, Elizabeth Maxwell, Ham Tyler, Howard K. Smith, John Langley, Kyle Bates, and others
