Historical clue formulations

• Voiced — 2017-12-20
• Like "n" and "r," in phonetics — 2017-03-22
• Voiced, in phonetics — 2015-01-24
• Voiced — 2011-06-26
• Voiced, in phonetics — 2010-01-17
• Voiced — 2003-03-08
• Voiced — 2003-01-12
• Having sound — 2002-10-13
• Speech sound — 2001-01-11
• Voiced — 2000-12-04
• Making noises — 2000-08-05
• Voiced — 1999-09-01
• Audible — 1996-04-07
• Voiced — 1995-05-27