The aim of this study was to evaluate the Auditory Steady-State Response (ASSR) and to compare the ASSR results with pure tone hearing levels. The ASSR of 7 adults with normal hearing and 6 patients with hearing loss between the ages of 64 and 183 months was examined. A relationship between the ASSR results and the pure tone hearing levels was observed, especially in subjects with higher degrees of hearing loss. On the basis of this data, we used this system to examine 3 hearing-impaired infants. The results were useful for the detection and diagnosis of hearing loss and for the fitting of hearing aids. The eary diagnosis of hearing loss is important for the development of listening and speech skills. Furthermore, much attention is needed for the detection of hearing loss in very young or developmentally delayed children. ASSR is useful for performing objective measurements of frequency-specific hearing levels.
This study investigated individual differences in the development of speech perception and language in seven children with congenital deafness, who had received cochlear implants and examined the factors that influenced their performance after implantation. The subjects were implanted with the Nuchleus-24 system between the ages of two and three years old and had been wearing the implants for two to three years. The subjects were evaluated using our original speech perception test and language and cognitive skill measures over time. The subjects were divided into three groups. The first group progressed remarkably in speech perception and language skills within a short period. The second group showed modest development, and the speech perception and language skills improved only slightly in the third group. The first group with the good outcome had already acquired some utterances before the implantation, and spoken language was recognized by the children after the implantation. The usage of both signed and spoken language was effective for the children with poor speech perception and language after the implantation. These children had other factors such as pervasive developmental disorders, suspected learning disorders, or slight mental retardation.
Delays, in digital signal processing by hearingaids may be perceived as an echo by wearers: their ears receive an unprocessed sound through the head and airway, while a delayed sound reaches the eardrum through the hearing aid because of the complexity of the digital processing. Recently, we prescribed a digital product (A) for a patient (I), who complained of an echo-like noise, presumably resulting from this kind of delay. To study the etiology of the noise, we retrospectively examined 98 ears of 77 patients (35 men and 42 women) who tried or bought Product A between 2002 and 2003 (age range, 24-89 years; mean age 67.9 years) (hearing acuity range, 25-92.5dB; mean, 52.6dB), We found that 8 ears in 6 patients, including Patient I, were improperly fitted. We analyzed the reasons for the improper fitting and compared the audiograms of fitted and unfitted patients. Among the 6 patients, Patient I and two others were delay-sensitive-their hearing was better, especially for lower frequencies. Further, we measured the delay levels (0.2-10.2ms) of Product A and 4 other products and observed that Product A had the longest delay. The productoriented delay time should be considered during the fitting of digital hearing aids in such patients.
To assess the usefulness of multiple auditory steady-state response (MASTER®) as an objective audiometry for waking adults, the auditory steady-state response (ASSR) using a multiple simultaneous stimulation technique and sinusoidally amplitude-modulated (SAM) tones modulated by modulation frequencies (MFs) around 40Hz and pure tone audiometry were performed in 11 adults (22 ears) with normal hearing and 3 hearing-impaired patients. The carrier frequency (CF)/MF combinations of the mixed SAM tones were set at 0.5kHz/32Hz, 1kHz/36Hz, 2kHz/40Hz and 4kHz/44Hz for the right ear and 0.5kHz/34Hz, 1kHz/38Hz, 2kHz/42Hz and 4kHz/46Hz for the left ear. The average differences and standard deviations between the ASSR threshold and the hearing level at each frequency ranged from 16.4 to 19.3dB and from 10.0 to 12.5dB, respectively. The ASSR threshold patterns corresponded fairly well to the audiograms. However, the differences between the ASSR threshold detected by MASTER® and the hearing level were about 5dB larger than those between the ASSR thresholds detected using the SAM tones with a single MF and the hearing level. These findings suggest that MASTER® using SAM tones modulated by MFs around 40Hz is sufficiently useful to be utilized as an objective audiometry for waking adults and that its frequency specificity is high enough to predict the audiogram pattern. However, the rather large error should be considered when used clinically.