unsounding

The big old grandfather clock at the top of the stairs pointed ten minutes past two, and the house was hushed of every sound save that which is the evidence of deep sleep, when the door of Cleek's room swung quietly open, and Cleek himself, in dressing-gown and wadded bedroom slippers, stepped out into the dark hall, and, leaving Dollops on guard, passed like a shadow over the thick, unsounding carpet.

Cleek: the Man of the Forty Faces Thomas W. Hanshew 1885

The big old grandfather clock at the top of the stairs pointed ten minutes past two, and the house was hushed of every sound save that which is the evidence of deep sleep, when the door of Cleek's room swung quietly open, and Cleek himself, in dressing-gown and wadded bedroom slippers, stepped out into the dark hall, and, leaving Dollops on guard, passed like a shadow over the thick, unsounding carpet.

Cleek, the Master Detective Thomas W. Hanshew 1885

Now there still remains the _Consonants_, or the Letters, which are formed out of an unsounding or mute _Breath_; yet, out of which, some of the _Semi-vowels_ may be made, as _g.ch. s.f. v. _

Surdus loquens. English John Conrade Amman 1696

I only hate the innacurate tuner and the unsounding Wah.

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(among the puns in still is unsounding) and a bearer "of silence and slow time" (Ode on a Grecian Urn 2), the time of reading slowed by the shift of pentameter into spondee.

Sounding Romantic: The Sound of Sound 2008