The analogy you provided is comparing two sets of words, where the first word in each set describes a sound and the second word is something associated with that sound.
"Wailing" is often associated with a "siren," as sirens produce a loud, wailing sound. Similarly, "whispered" is associated with a "secret," as whispers are often used to convey secrets.
Therefore, the correct answer to complete the analogy is:
Wailing: Siren :: Whispered: Secret
So the answer is Siren.