Historical clue formulations

• Flat sound — 2012-08-09
• Flat sound — 2008-10-02
• Deflation indication — 2008-06-07
• Flat sound — 2007-09-06
• Deflation indicator — 2006-10-20
• Bacon sizzle — 2005-12-02
• Air hose sound — 2004-03-13
• Flat tire indicator — 2004-03-11
• Radiator sound — 2002-06-17
• Sound of a leak — 2002-04-02
• Sound of a leak — 2000-12-24
• Not a good sound for a balloonist — 2000-06-11
• Radiator sound — 1998-11-01
• Kettle sound — 1997-05-31
• Sound of a live wire — 1994-06-09