To define the various levels of hearing impairment, we used the WHO classification system that is based on the pure-tone average
of four frequencies (500, 1,000, 2,000, and 4,000 Hz) in the better-hearing ear.
defined hearing loss as "a pure-tone average
of thresholds at 500, 1,000, 2,000, and 4,000 Hz greater than 25 dB" in the worse ear .
The researchers evaluated hearing impairment as a pure-tone average
greater than 25 decibels hearing level in either ear, and also measured word recognition at different sound levels and with male and female voices.
Successful treatment was defined as at least a 50% recovery of four-frequency pure-tone average
relative to the unaffected, contralateral ear.
Participants' demographics and hearing loss (as graded by the ASHA degree of severity of hearing loss) Participants, N 25 Age (years), mean (range) 43 (15-86) Age distribution (years), n 15-20 4 21-40 7 41-60 6 61-80 8 Gender, n Male 13 Female 12 Ears with PTA (dB), n [less than or equal to] 25 (normal) 24 26-40 (mild loss) 18 41-55 (moderate loss) 5 56-70 (moderate to severe loss) 2 71-90 (severe loss) 1 [greater than or equal to] 91 (profound loss) 0 ASHA = American Speech-Language-Hearing Association; PTA = pure-tone average
scores at 500, 1,000, and 2,000 Hz revealed a 95-dB hearing loss on the right and a 15-dB loss on the left.
Audiometry revealed a conductive hearing loss, as the air-conduction pure-tone average
(PTA) was 41 dB and the bone-conduction PTA was 10 dB.
The mean pure-tone average
was 36 dB (SD = 21) before therapy and remained the same after therapy, revealing no significant overall change in hearing.
The result was a reduction of the air-bone gap of 20 dB and a mean pure-tone average
of 16 dB.
The results on the right fell entirely within normal limits; the pure-tone average
(PTA) for the three central frequencies was 8 dB.
Hearing on the right was normal with a pure-tone average
threshold of 5 dB.
The SRT is normally 10 dB higher than the pure-tone average
(PTA) at 0.