"sibilations" in the noun sense
1. hiss, hissing, hushing, fizzle, sibilation
a fricative sound (especially as an expression of disapproval
"the performers could not be heard over the hissing of the audience"
2. sibilation, assibilation
pronunciation with a sibilant (hissing or whistling) sound
Source: WordNet® (An amazing lexical database of English)
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