Sensorineural hearing loss compresses the full loudness range into fewer decibels

Evidence

Sensorineural hearing loss (SNHL) has a robust and profound effect on loudness, with a primary effect being abnormally rapid growth of loudness. Fowler (1928) was the first to report that listeners with SNHL experienced a similar range of loudness (from very soft to uncomfortably loud) but over a smaller range of decibel levels due to reduced audibility. He dubbed this phenomenon loudness recruitment. Numerous studies have followed Fowler’s initial observations, and an illustration of loudness growth in listeners with SNHL is illustrated in Figure 4–14, which shows a sample loudness growth function for a listener with 40 dB hearing loss plotted along with a loudness growth for a listener with normal hearing. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 838

Fowler conducted numerous studies on measuring absolute thresholds in listeners with hearing loss. He was the first to report that listeners with sensorineural hearing loss experience a smaller dynamic range but a similar range of loudness as listeners with normal hearing. He called this phenomenon loudness recruitment (Fowler, 1928), a term we still adopt today. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 100

Categorization

• DEFINE: Defines ‘loudness recruitment’ — listeners with SNHL experience the full loudness range compressed into a smaller dB span.
• QUESTION: What mechanism explains how dynamic range shrinks while total loudness range stays similar? This seems like a paradox worth understanding at the cochlear level.
• CANDY: A neat, tweetable paradox: hard-of-hearing listeners feel loudness just as intensely but compress the whole usable range.
• XREF: Connects to the reader’s whole stated purpose — this is the founding concept distinguishing normal from impaired hearing perception. — connects to: Recruitment can explain why loudness summation is absent in noise-induced hearing loss — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1960; Noise-induced hearing loss begins with impairment of outer hair cells; Hearing loss widens critical bands and alters music perception itself — Toole, Floyd E, Sound reproduction- the acoustics and…, 1897 (+8 more)
• corroborated: 4 independent passages support this claim — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 838; Jennifer Lentz, Psychoacoustics- Perception of Normal…, 100

Broader Connections

• Hearing loss squeezes the full loudness range into a much smaller dynamic range #corroborates (1.00)