[The optimal stimulation parameters of the free-field auditory steady-state responses].

UNLABELLED

Studies of the recent years are devoted to using the auditory steady-state responses (ASSR) as an evaluation method of amplification outcomes. In this case stimulation is performed in the sound field via loudspeaker with a hearing aid (HA) in patient's ear.

GOAL

Estimation the optimal stimulation parameters of ASSR in free field, which provide maximum correlation with behavioral thresholds.

MATERIALS AND METHODS

26 subjects were included in the study: 10 with normal hearing (4 adults and 6 children) and 16 children (1-16 years old) with sensorineural hearing loss (SNHL). Aided and unaided ASSR thresholds were compared with corresponding behavioral thresholds (BT). All recordings were conducted in free sound field. We used mono-frequency stimulation method at 500-4000 Hz career frequencies. Modulation frequency was set as 40 Hz. Types of stimuli modulation: AM/FM modulation, exponential modulation (AM), three carrier frequencies and modulated Chirp-tone (Chirp).

RESULTS

In normal hearing subjects the difference between ASSR and BT varied from 0 dB to 35 dB, and the significant correlation between them was observed (<0.05). The maximum difference between ASSR and BT in children with SNHL was at 500 Hz (15.6±4.3 dB), minimum - at 2 and 4 kHz (8±2.9 dB and 7±3 dB respectively). In aided condition maximum difference was detected at 500 Hz (10.2±3.8 dB), minimum - at 1 and 2 kHz (7.8±2.8 and 7.3±3.1 dB respectively). We got significantly less difference between ASSR and BT in all test conditions using following types of stimuli: at 500 Hz and 1000 Hz - AM (<0.01); at 2 and 4 kHz - Chirp (<0.05 and <0.01 respectively). Thereby, free field ASSR might be used as an objective method of evaluation the amplification outcomes in children with SNHL.