Harmonic bands crowd closer together as frequency rises because of the ERB scale.

Evidence

For the sound consisting of the first five harmonics, it can be seen that these are isolated separately as five horizontal bands of energy. These harmonic bands of energy become closer together with increasing frequency on the spectrogram due to the nature of the ERB frequency scale. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1503

Categorization

• DEFINE: Explains why the ERB frequency scale distorts spectrogram spacing rather than being linear in Hz.
• XREF: connects to: Strong energy above the fifth harmonic makes instruments sound bright — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1475; Loudness at high sound levels arises from excitation spreading across adjacent frequency bands; Unresolved harmonics smear together as frequency rises (+6 more)

Broader Connections

• Unresolved harmonics smear together as frequency rises #expands (0.95)
• Harmonics cease being resolved when their spacing falls below the ERB #corroborates (0.95) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1505
• Harmonics resolve only while their spacing exceeds the ear’s ERB #corroborates (0.95)
• Widening a sound’s bandwidth beyond one critical band raises perceived loudness at unchanged intensity. #expands (0.90) — David Howard, Jamie Angus, coustics and Psychoacoustics, 653
• Loudness grows when sound energy spills beyond a single critical band #expands (0.90) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 667
• Loudness at high sound levels arises from excitation spreading across adjacent frequency bands #qualifies (0.85)
• The ear groups sound into critical frequency bands that shape loudness perception #qualifies (0.85)
• Spreading a sound’s energy across more critical bands increases perceived loudness without raising intensity #qualifies (0.80) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 665