Summary of derived variables
| Construct/measures | Definitions | Rationale |
| Continuous | ||
| High Fletcher Index | The average of thresholds at 1, 2 and 4 kHz | Best reflects audibility at speech frequencies |
| Four frequency average | The average of thresholds at 1, 2, 4 and 8 kHz | Reflects audibility at usual speech+high frequencies |
| Lower frequency average | The average of thresholds at 1 and 2 kHz | Reflects audibility of lower frequency speech sounds, for example, most vowels and letter combinations /ng//ch/, /sh/; characteristic of conductive or sensorineural hearing loss |
| Higher frequency average | The average of thresholds at 4 and 8 kHz | Reflects audibility of higher frequency speech sounds, for example, most consonant and letter combinations /th/; particularly disabling with background noise; suggests noise-induced and/or sensorineural hearing loss |
| Categorical | ||
| Unilateral hearing loss | Hearing thresholds ≥16 dB HL in worse hearing ear and hearing thresholds is ≤15 dB HL in better hearing ear | Hearing loss in one ear |
| Bilateral hearing loss | Hearing thresholds is ≥16 dB HL in better hearing ear | Hearing loss in both ears |
| Type A tympanogram | Ear canal volume: 0.6–1.5 cm3; middle ear pressure: −100 to +50 daPa; compliance: 0.25–1.4 mmho | Suggests normal middle ear function |
| Type B tympanogram | Ear canal volume: 0.6–1.5 cm3; middle ear pressure: −100 to +50 daPa; compliance: <0.25 mmho | Suggests middle ear effusion, tympanic membrane perforation, cerumen occlusion or a probe sealed against the canal wall |
| Type C tympanogram | Ear canal volume: 0.6–1.5 cm3; middle ear pressure: <−100 daPa; compliance: 0.25–1.4 mmho | Suggests negative middle ear pressure |
db HL, decibels hearing level.