unvoiced (adj.)

• echoless
• hushed
• inaudible
• mousy
• noiseless
• quiescent
• quiet
• silent
• soundless
• still
• stilly
• tacit
• unarticulated
• undeclared
• unexpressed
• unhearable
• unpublished
• unrecorded
• unsaid
• unsounded
• unspoken
• unsung
• untold
• unuttered
• unwritten
• wordless