subvocal

Only the force of long training and habit kept him from shouting the words aloud instead of keeping them to a subvocal whisper.

I let out a subvocal squeal and was pitched forward as the ride system shuddered to a stop.

Hayden does not distinguish the subvocal and aspirate th in Omaha.

Orne touched the subvocal stud at his neck, moved his speaking muscles without opening his mouth.