Zero decibels is a perceptual threshold, not a true physical absence of sound

Evidence

The anechoic chamber in this building is rated to minus 9.4 decibels, A-weighted, 69,000 times lower in intensity than the quiet of the conference room and eight times lower than zero decibels. Orfield reminds me that zero decibels is not an absolute measurement but simply the point below which a person with unimpaired hearing no longer perceives sound. — George Michelsen Foy, Zero Decibels, 473

Categorization

• corroborated: 2 independent passages support this claim — George Michelsen Foy, Zero Decibels: The Quest for Absolute…, 473
• XREF: connects to: The act of hearing itself may make true absolute silence unattainable — George Michelsen Foy, Zero Decibels: The Quest for Absolute…, 526; Pure, absolute silence has never existed and cannot exist — George Michelsen Foy, Zero Decibels: The Quest for Absolute…, 603; Near-total silence reveals that most people generate internal sound perceived as tinnitus — George Michelsen Foy, Zero Decibels: The Quest for Absolute…, 571 (+12 more)

Library Connections

• Perceived loudness and physical sound intensity follow different, non-intuitive mathematical scales #corroborates (0.85) — George Michelsen Foy, Zero Decibels, 53

Broader Connections

• A perfect unchanging sound would be perceived as silence. #qualifies (0.75) — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 881