Standards accept up to 25 dB of hearing loss as medically normal

Evidence

All participants had normal hearing bilaterally, defined by four frequency average hearing loss thresholds (500 Hz, 1 kHz, 2 kHz and 4 kHz) of less than 25 dB HL. — Dijk, Pim van, Physiology, Psychoacoustics and…, 4163 (#corroborates, via linked claim)

Consider, for example, the audiogram for damaged hearing given in Figure 2.19. Here, the average dBHL value for frequencies 250 Hz to 4 kHz would be {((10 + 5 + 5 + 15 + 60)/5) = 19 dBHL}, which indicates “no hearing handicap” (see Table 7.1), which is clearly not the case. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2360 (#qualifies, via linked claim)

Categorization

• XREF: connects to: Occupational hearing guidelines permit hearing loss rather than prevent it; Normal hearing is operationally defined as a four-frequency average threshold below 25 dB HL. — Dijk, Pim van, Physiology, Psychoacoustics and…, 4163; Averaging hearing loss across frequencies can mask serious impairment — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2360 (+2 more)

Broader Connections

• Normal hearing is operationally defined as a four-frequency average threshold below 25 dB HL. #corroborates (0.95) — Dijk, Pim van, Physiology, Psychoacoustics and…, 4163
• WHO defines disabling hearing loss as a 40 dB threshold shift for adults #expands (0.80)
• Averaging hearing loss across frequencies can mask serious impairment #qualifies (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2360
• Hearing thresholds are clinically tested at octave-spaced frequencies covering the speech range #expands (0.70)