sibilator

/ˈsɪbɪleɪtər/
noun
  1. A person or thing that makes a hissing sound.
    • In the recording, you can hear a sibilator in the background, like air escaping from a tire.
    • The snake charmer's flute acted as a sibilator, producing a soft hiss to calm the cobra.
    • The old radiator was a constant sibilator, hissing steam all night.
Synonyms