Historical clue formulations

• A voice might be heard within this — 2022-04-05
• Eavesdropping range — 2021-11-29
• Range within which you can answer the question "Can you hear me now?" — 2021-06-13
• Eavesdropping distance — 2013-11-20
• Hearing range — 2013-05-22
• Secrets are usually not revealed in this — 2010-05-21
• Some sounds are in it — 2005-03-25
• You can't hear if you're out of it — 1999-04-04
• Hearing range — 1995-09-06