Birdsong variations can be visualized as sonograms paired with faces

Evidence

Back in the mid-1980s, when I was a bicycle messenger, Professor Beecher invited me to his lab and showed me what amounts to photo albums of facial characteristics paired with sonograms—visual printouts of very minute changes in emitted calls. — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 935

Categorization

• XREF: The sonogram-as-photo-album frame echoes the book’s core method of making sound visible and legible to non-specialists. — connects to: Sonograms visually expose vowel formants as enhanced frequency bands
• corroborated: 2 independent passages support this claim — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 935