Record #00515Technology archive
Orfield Laboratories' anechoic chamber in Minneapolis, Minnesota, recorded an ambient level of −24.9 dBA on 19 November 2021, establishing the quietest formally measured anechoic-room record.
Current Record
-24.9dBA
Current record value
The chamber uses nested masonry and steel isolation structures, spring-supported inner space and glass-fibre acoustic wedges to limit vibration transmission and suppress reflections. A suspended mesh floor allows the wedges to cover the lower surfaces.
Because the measured background approaches or falls below microphone self-noise, technicians correlated signals from two independent microphones to isolate shared acoustic information from uncorrelated electrical noise. The laboratory also held earlier quiet-room records in 2004 and 2012.
The record conclusion has sufficient verification support.
Basis: direct confirmation by an authority
Guinness documents −24.9 dBA on 19 November 2021 at Orfield's chamber; the operator confirms its previous 2004 and 2012 records. This is A-weighted sound-pressure level measured by microphone cross-correlation, not absolute silence or negative acoustic energy.
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