What might cause a commercial to sound "hollow" with missing voices on a monophonic TV set?

A commercial might sound "hollow" with missing voices on a monophonic TV set due to phase reversal in the audio channels. In monophonic audio systems, sound is mixed into a single channel. If there is a phase reversal—meaning the audio signals are out of alignment in such a way that when one speaker plays a sound wave, the other speaker plays the same sound wave but inverted—this can lead to certain frequencies canceling each other out. As a result, certain components of the audio, such as vocals, may become significantly diminished or disappear entirely from what the listener hears, leading to a hollow sound.

In contrast, while weak signal strength could lead to overall audio degradation, it typically doesn't cause specific elements like voices to disappear. Insufficient bandwidth might limit the clarity or fidelity of the audio, but it does not specifically reference the phasing issue that results in vocal loss. Audio filtering issues could affect sound quality, but they wouldn't inherently create the distinct "hollow" sound caused by phase cancellation. Hence, the issue of phase reversal is the most accurate explanation for the scenario described.