Closing one ear barely changes perceived loudness of live speech

Evidence

Ecological validity may be enhanced when an external source is used, when that source is speech, particularly connected speech rather than isolated words, and when accompanied by coherent visual cues. Since all these conditions are fulfilled when listening to someone in real life, the phenomenon of loudness constancy can be compellingly, if informally, demonstrated by simply occluding one ear with a finger when listening to someone talk; most people report that no change in loudness is apparent. — Dijk, Pim van, Physiology, Psychoacoustics and…, 1525

Categorization

• SEED: The finger-in-ear demonstration is a brilliant classroom or public-science demo contradicting textbook summation rules.
• CANDY: A fun, immediately testable fact to share at dinner: put a finger in one ear while someone talks and the speech stays equally loud.