Fletcher defined critical bands as noise regions whose power equals a just-masked tone’s

Evidence

The concept of critical bands was proposed by Fletcher. He assumed that the part of a noise that is effective in masking a test tone is the part of its spectrum lying near the tone. In order to gain not only relative values but also absolute values, the following additional assumption was made: masking is achieved when the power of the tone and the power of that part of the noise spectrum lying near the tone and producing the masking effect are the same; parts of the noise outside the spectrum near the test tone do not contribute to masking. Characteristic frequency bands defined in this way have a bandwidth that produces the same acoustic power in the tone and in the noise spectrum within that band when the tone is just masked. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 865

Categorization

• DEFINE: Clarifies precisely how Fletcher operationalized the critical band concept, distinguishing it from later measurement approaches.
• corroborated: 2 independent passages support this claim — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 865
• XREF: connects to: Masked threshold of a tone by white noise is computable from critical-band level; Critical-band intensity derivation yields triangular patterns for noise and rectangular ones for tones.; Critical bands govern tonal discrimination and timbre, not overall hearing resolution (+6 more)

Broader Connections

• Masked threshold of a tone by white noise is computable from critical-band level #expands (0.95)
• Masking acts within critical bandwidths, leaving distant-frequency sounds unaffected #expands (0.90) — Eric J. Heller, Why You Hear What You Hear- An…, 2009
• Narrowband noise at a given frequency masks nearby tones much more than distant ones #expands (0.90)
• Uniform exciting noise delivers equal intensity to every critical band #qualifies (0.85) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1189
• Critical-band intensity derivation yields triangular patterns for noise and rectangular ones for tones. #expands (0.82)
• Critical band bandwidths grow from 100 Hz to over 2 kHz with frequency #expands (0.80)
• Critical bands govern tonal discrimination and timbre, not overall hearing resolution #expands (0.78)
• Clinical masking directly applies Fletcher’s critical band theory #exemplifies (0.75)
• Critical bandwidth is measured through masking effects rather than direct perception #corroborates (0.72) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 585