Historical clue formulations

• Acoustic measure — 2022-04-21
• Volume measure — 2017-12-09
• Aural measure — 2015-10-31
• Unit of loudness — 2014-10-15
• Volume measure — 2013-10-18
• Loudness unit — 2012-08-05
• Loudness unit — 2011-05-15
• Loudness unit — 2010-01-13
• Loudness unit — 2007-11-24
• Loudness measure — 2006-12-03
• Unit of volume — 2004-12-12
• Sound amount — 2000-06-24
• Loudness unit — 1998-09-26
• Unit of loudness — 1997-11-12
• Loudness unit — 1997-10-03
• Loudness measure — 1997-07-13
• Sound measure — 1995-11-16
• Loudness measure — 1994-10-08
• Loudness unit — 1994-09-07
• Loudness unit — 1994-05-08