Evoked Auditory Responses in Heading Impaired

Abstract

The Evoked Auditory Responses in Hearing Impaired database contains evoked Auditory Brainstem Response (ABR) and Otoacoustic Emission (OAE) recordings in eight hearing impaired listeners, in response to tone-burst stimuli across a wide range of levels.

Data Collection

Eight listeners (four females, four males, ages 40 to 85), with a known history of hearing impairment confirmed through clinical tests (audiometric measurements made in the Northeastern University Speech-Language, and Hearing Center), and thresholds higher than 25 dB HL (at least one octave frequency between 250 Hz to 8 kHz), participated in all measurements. Listeners were tested on the ear that had the best (lowest) thresholds determined through a 2-interval, 2-alternative forced-choice procedure with the exact stimuli used throughout the experiment. This choice of ear was made to ensure that measurements could be made over the maximum physical and perceptual stimulus ranges.

Three listeners were tested on the left ear and five listeners were tested on the right ear. Three listeners could not be tested at 4 kHz because their thresholds were higher than 85 dB peak-equivalent sound pressure level (peSPL).

The tone bursts used were 1-kHz tones with 4 ms duration and 4-kHz tones with 1 ms duration. The stimuli were multiplied with a Gaussian window and then end-padded with silence to generate a stimulus length of 41.7 ms. The Gaussian window was generated through the MATLAB function GAUSSWIN, which resulted in attenuations of about 27 dB at the start (0) and end times (1 or 4 ms) of the tone burst. The lack of a steady-state region in the window (i.e., no plateau) helped ensure consistent root mean square (RMS) values, equal spectral dispersion on a logarithmic scale, and a good TBABR response to transient stimuli. The stimulus levels varied from 5 dB below the listener’s threshold to 100 dB peSPL in steps of 5 dB. Levels matched the specifications of the voltage-to-level conversion provided by Etymotic Research for the ER-10C apparatus.

The stimuli were generated in MATLAB (2006b running on Ubuntu) and converted from digital (48-kHz sampling frequency) to analog using a 24-bit Lynx Two sound card. The analog signal was then passed through a Tucker-Davis Technologies HB7 headphone buffer and presented monaurally via the two transducers of the Etymotic ER-10C to a listener inside a double-walled sound-attenuating booth. During the TBOAE and TBABR measurements, the recordings from the ER-10C were converted from analog to digital (48 kHz sampling frequency) via a Lynx Two sound card. Routine calibration for each system was performed to test for proper wiring and ER-10C output in a plastic syringe coupler provided by Etymotic. All levels were determined using RMS of the windowed signal relative to the specifications which were provided by Etymotic and verified by doing an actual in ear measurement for a single listener using a Fonix 6500-CX real-ear system.

Data Files

The data files are provided in standard WFDB format, named: hA_B_CkHz_D_E - where A is the subject number, B is the ear used, C is the stimulus frequency, D is the stimulus level in dB SPL, and E is the trial number of the given stimulus level and frequency. They are stored in subdirectories named after the subject number

The Listener_MetaData.txt file includes each subject's age, gender, and 2-interval 2-alternative forced-choice thresholds in dB peSPL at 1 kHz (and 4 kHz for some subjects).

The HX_LoudnessData_FY.txt files contain estimated loudness curve functions as a function of sound pressure level at YkHz.

Contributors

This data was contributed by Ikaro Silvia (ikarosilva at ieee dot org). See also the Evoked Auditory Responses in Normals across Stimulus Level database.