Free-field hearing thresholds can exceed headphone thresholds by over 15 dB

Evidence

Absolute thresholds collected from freefield measures can be more than 15 dB better than testing over headphones. Acoustic interactions between the sound and the body, amplification by anatomical structures, and binaural effects contribute to these differences. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 351

Categorization

• QUESTION: Which anatomical structures amplify what frequencies to create free-field advantages? Worth tracing in a later chapter on sound conduction.
• SHARE: For an audiologist friend who calibrates test setups — the 15 dB free-field vs. headphone gap is a practical calibration reminder.