Final answer:
Dead air is considered a taboo in the radio industry because it can indicate unprofessionalism and lead to audience loss. The observed frequency of sound does not become infinite when the source moves at the speed of sound, which makes that statement false.
Step-by-step explanation:
The question "Dead air is a taboo in the radio industry" evaluates a commonly held belief in broadcasting. Dead air refers to unintended silence on air, which is generally considered to be a negative occurrence in radio broadcasting because it can cause listener discomfort or tune-out. The assertion is true; dead air is indeed a taboo in the radio industry as it can reflect unprofessionalism and result in lost audiences.
Regarding the additional statement provided for reference, "The observed frequency becomes infinite when the source is moving at the speed of sound," the correct answer is false. When the source of a sound moves at the speed of sound, a phenomenon known as a sonic boom occurs, and the frequencies are layered upon one another at the same point, but they do not become infinite.