Turning down volume suppresses perceived bass and treble relative to midrange

Evidence

The phon scale is a subjective scale of loudness based on the judgments of listeners to match the loudness of tones to reference tones at 1 kHz. The curve for N phones intersects 1 kHz at N dB(SPL) by definition, and it can be seen that the relative shape of the phon curves flattens out at higher sound levels, as shown in Figure 2.13. The relative loudness of different frequencies is not preserved, and therefore the perceived frequency balance of sound varies as the listening level is altered. This is an effect we have all heard when the volume of a recording is turned down and the bass and treble components appear suppressed relative to the midrange frequencies, and the sound becomes “duller” and “thinner.” — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 626

The loudness of sine wave signals, as a function of their frequencies and sound pressure levels, is given by the “phon” scale. The phon scale is a subjective scale of loudness based on the judgments of listeners to match the loudness of tones to reference tones at 1 kHz. The curve for N phones intersects 1 kHz at N dB(SPL) by definition, and it can be seen that the relative shape of the phon curves flattens out at higher sound levels, as shown in Figure 2.13. The relative loudness of different frequencies is not preserved, and therefore the perceived frequency balance of sound varies as the listening level is altered. This is an effect we have all heard when the volume of a recording is turned down and the bass and treble components appear suppressed relative to the midrange frequencies, and the sound becomes “duller” and “thinner.” Ideally, we should listen to reproduced sound at the level at which it was originally recorded. However, in most cases this would be antisocial, especially as much rock material is mixed at levels in excess of 100 dB(SPL)! — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 626

Categorization

• DEFINE: Defines the phon scale conceptually and its 1 kHz anchor.
• XREF: Directly explains why quiet playback sounds dull — connects to loudness curves and to mixing/mastering practice. — connects to: Adding lower-frequency sound can decrease perceived sharpness — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1350; Room resonance excess masks loudspeaker bass deficiency to listeners — Toole, Floyd E, Sound reproduction- the acoustics and…, 549; Reduced playback levels cause timbral shifts and lost low bass (+8 more)
• SEED: Could fuel an essay on why ‘turning it up’ always makes music feel fuller and more alive.
• ADDENDUM: Explains why loudness normalization and level-matching matter; the ‘duller, thinner’ effect at low volume is a concrete mechanism relevant to the tree-as-infrastructure essay’s listening themes.
• corroborated: 3 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 626