sibilation

Challenger walked across to the oxygen tube, and the sound of the loud hissing fell away till it was the most gentle sibilation.

Boardman appeared shocked, and yet somewhat amused; he made a soft low sibilation between his teeth.

In place of martial airs and musical utterance, there rose upon the ear a strange din of harsh gutturals and singular sibilation.

They make it clear and penetrating; yet it seems a poor, effeminate sibilation, and no generous, open-mouthed call.

Bob whistled,—a long sibilation of amazement,—and then laughed and laughed again.