AMELIORATIVE EFFECT OF CUSTOMIZED SOUND STIMULATION ON SENSORINEURAL HEARING LOSS
Sangyeop Kwak, Seoyoung Kim, Yunjeong Bae, and Eunyee Kwak
Earlogic Corporation, Los Angeles, USA / Earlogic Clinic and Earlogic Auditory Research Institute, Seoul, Korea

ABSTRACT
Sound conditioning (i.e., prior exposure to low-level sounds) has been known to protect hearing ability against damage by traumatic noise in a number of mammalian species, including humans. It has also been reported that acoustic stimuli can slow progressive sensorineural hearing loss. Thus, exposure to a moderately augmented acoustic environment could delay the loss of auditory function in mice. In addition to these protection and retardation effects, long-term sound conditioning could enhance cochlear sensitivity in normal hearing guinea pigs. In this study, we applied customized sound stimuli to 30 patients with sensorineural hearing loss and compared the hearing thresholds before and after sound stimulation to investigate if the sound stimulation could change hearing ability. The results showed that acoustic stimuli could significantly improve hearing ability.

TINNITUS SPECTRUM AND ITS REALTIME VISUALIZATION BASED ON 134 BANDS COCHLEAR MODEL
Sangyeop Kwak, Seoyoung Kim, Yunjeong Bae, and Eunyee Kwak
Earlogic Corporation, Los Angeles, USA / Earlogic Clinic and Earlogic Auditory Research Institute, Seoul, Korea

ABSTRACT
The existing method for matching tinnitus relies on the paradigm for listening single pure tone or band pass filtered noise. There are many types of tinnitus spectrum in accordance with hearing loss regions; 1) single pure tone, 2) multiple pure tones (harmonic or non-harmonic complex tone), 3) single filtered noise, 4) multiple filtered noise, and 5) the combination of 1)~4). In this respect, a new method has been designed to achieve accurate performance for finding various types of tinnitus spectrum. This study suggests two inventions; 1) tinnitus taxonomy based on 10 types of tinnitus spectrum and 2) a method for visualization of tinnitus spectrum using 3D cochlear model with 134 bands (1/24 Oct) frequency resolution.

ABSTRACT
To investigate if hearing ability could be improved by sound stimulation, we applied customized sound stimuli to 9 patients with sensorineural hearing loss, and compared behavioral hearing thresholds before and after sound
stimulation. The results of this study showed that acoustic stimuli could improve hearing ability. On overall average,
the behavioral hearing threshold decreased by 8.91 dB after 2 weeks of sound stimulation followed by a 2 week break.

A NEW METHOD FOR RESTORATION OF SENSORINEURAL HEARING LOSS: A PROSPECTIVE CLINICAL STUDY
Eunyee Kwak, Sangyeop Kwak, Sookjin Song, Seonwoo Kim, and Sung Hwa Hong
Earlogic Auditory Research Institute and Earlogic Korea Inc., Seoul, Republic of Korea
Department of Otorhinolaryngology-Head and Neck Surgery, Samsung Medical Center, Seoul, Republic of Korea

ABSTRACT
Sensorineural hearing loss, one of the most common diseases, has historically been regarded as an incurable and irreversible condition. The number of people with hearing loss has grown rapidly in recent years, because of the prevalence of environmental noise and the increase in the elderly population. Although hearing aids are provided as an alternative device to help hearing impaired people, no fundamental treatment is currently available. Several studies have shown that noise-induced hearing loss can be prevented by prior exposure to low-levels of acoustic stimuli, a procedure known as sound conditioning. However, to our knowledge, this is the first clinical study to evaluate the effects of sound conditioning on hearing restoration.

AUDITORY NOTCHES IN 134 BAND AUDIOGRAMS (AUTOMATED MICRO AUDIOMETER: AMA-PTA)
Eunyee Kwak, Sookjin Song, and Sangyeop Kwak
Earlogic Corporation, 3550 Wilshire Blvd. Suite 510, Los Angeles, U.S.A.

ABSTRACT
Several studies reported the prevalence of auditory notches. Auditory notches could be found in subjects with normal Hearing sensitivity as well as hearing-impaired subjects. To investigate the profile of threshold microstructure in human auditory system, frequency profiles of auditory notches were obtained from normal-hearing subjects. To identify the frequency of auditory notches, 134 band (1/24 Oct. resolution in 250~12,000Hz) pure-tone audiometry was performed by using automated and randomized Bekesy audiometry (AMA-PTA). AMA-PTA enabled to obtain 134 band audiogram within 35~45 minutes. The 134 band audiograms were compared with 6band (1 Oct. resolution) audiograms. Auditory notches were observed in both ears of all subjects. However, the 6 band audiograms have missed most of the auditory notches observed in the 134 band audiograms. These auditory notches, which were not shown in conventional audiometry, were also observed in hearing-impaired subjects as well. This study demonstrates that the conventional, 6 band audiometry has overlooked the microstructure of auditory thresholds.

NEW METHOD TO ACQUIRE FREQUENCY-SPECIFIC THRESHOLDS BY BERA (ABR)
Eunyee Kwak, Sookjin Song, and Sangyeop Kwak
Earlogic Corporation, 3550 Wilshire Blvd. Suite 510, Los Angeles, U.S.A.

ABSTRACT
In the present study, we suggest a new automated method to acquire an objective frequency-specific audiogram by comparing the amplitude of Wave V with that of SN10. To increase signal to noise ratio in the automated ABR, the following three complementary controls called "triple artifact-rejection method" were adopted: (1) filtering periodic artifacts by real-time FFT monitoring, (2) randomization of ISI (inter-stimulus interval) to exclude periodic artifact influxed from the spontaneous potential, i.e., EEG, and (3) filtering fast component artifacts. To shorten test time without any deterioration of accuracy, "automated quasi Bekesy method" was adopted in the automated ABR. Hearing thresholds obtained from PTA (pure tone audiometry) were compared with those of the present automated ABR at 0.5, 1, 2, 4 KHz. The automated ABR predicted well the behavioral thresholds. Most importantly, there was a big time saving in the automated ABR proposed by the present study. That is, it took only 6~8 minutes which were only one-tenth of the testing time required for the conventional tone-pip ABR audiometry.

EFFECTS OF STIMULUS DURATION ON WAVE V AND N1 PEAK
Eunyee Kwak, Sookjin Song, and Sangyeop Kwak
Earlogic Corporation, 3550 Wilshire Blvd. Suite 510, Los Angeles, U.S.A.

ABSTRACT
Various stimulus parameters affect on auditory evoked brainstem response (ABR) and long-latency cortical response. Among them are stimulus intensity, repetition rate, rise-fall time, duration, and inter-stimulus interval (ISI). To investigate the effects of stimulus duration on Wave V and N1 peak, two types of tone-bursts with different duration (2-1-2 vs 2-46-2) were presented as stimuli. Since there is a controversy on the duration effects on Wave V amplitude, we intended to exclude both repetition rate and ISI effects. To this end, considerably long ISI (i.e. 250 ms) was set for Wave V detection. Significant differences in the amplitudes of Wave V and N1 were observed between 2-1-2 and 2-46-2 tone-bursts. Interestingly, increment of stimulus duration caused opposite effects on Wave V and N1 amplitude. While N1 amplitude increased with duration increment as previously reported, Wave V amplitude decreased when the longer stimulus was presented. These results demonstrate that stimulus duration may have opposite effects on ABR and auditory cortical responses.

THE EFFECT OF OTOACOUSTIC EMISSIONS ON THE EFFERENT AUDITORY FEEDBACK IN MUSIC COGNITION
Sangyeop Kwak and Roger A. Kendall, Music Cognition and Acoustics Laboratory,
Program in Systematic Musicology, University of California, Los Angeles (UCLA),

ABSTRACT
This study introduces two phenomena. One is “otoacoustic emission” which is a well-known audiological phenomenon, and the other is “efferent feedback dependency” which was the subject of the present study. An additional finding that the otoacoustic emissions (OAEs) spectra have a significant relationship to the each frequency value of equal-tempered scale suggests the musical significance of the efferent auditory feedback dependency. The experimental results and statistical analyses demonstrate the different effect of the efferent feedback dependency between the equal-tempered pitch and the 50 cents-higher pitch, and predict the presence of the central auditory filters, i.e., “chromatic circuit template.”