Jun-il Sohn

Phoneme-Based Self Hearing Assessment on a Smartphone

Phonemes provide an interesting alternative to pure tones in hearing tests. We propose a new smartphone-based method for self-hearing assessment using the four Korean phonemes which are similar to the English phonemes /a/, /i/, /sh/, and /s/. We conducted tests on 15 subjects diagnosed with mild to severe hearing loss and estimated their conventional pure-tone hearing thresholds from their phoneme hearing thresholds using regression analysis. The phoneme-based self-hearing assessment was found to be sufficiently reliable in estimating the hearing thresholds of hearing-impaired subjects. The difference between the hearing thresholds obtained through conventional pure-tone audiometry and those obtained using our method was 5.6 dB HL on average. The proposed hearing assessment was able to significantly reduce the mean test time compared to conventional pure-tone audiometry.

Al-PLAPH (Aluminum-PLANarization by Post-Heating) process for planarized double metal CMOS applications

Contact planarization in ULSI multi-level interconnections has been achieved by using a newly developed contact filling technology called Al-PLAPH (Aluminum-Planarization by Post-Heating). In the Al-PLAPH process, Al was initially deposited at room temperature without any substrate bias followed by an annealing step without breaking vacuum. In-situ annealing was carried out at a temperature range of 400 degrees C approximately 550 degrees C in a vacuum-isolated modular sputtering system. Sub-micron contacts with high-aspect-ratio (>or=1) were completely filled by heating above 500 degrees C. The process has been applied to a full CMOS device which did not show any degradation of electrical characteristics such as contact resistance and junction leakage. Reliability tests with line test patterns revealed better electromigration resistance with enhanced stress migration tolerance than conventionally grown Al lines.<<ETX>>

Robust adaptive feedback canceller based on modified pseudo affine projection algorithm

This paper presents an adaptive feedback cancellation (AFC) algorithm with robust and stable performance. The proposed algorithm is based on the pseudo affine projection (PAP) algorithm which approximates the affine projection (AP) with a complexity comparable to the NLMS. Direct application of the PAP to AFC, however, often exhibits instability because of the delayed estimate of the linear prediction (LP) coefficients. This problem is solved in the proposed algorithm by utilizing an inverse gain filter (IGF) before the update of adaptive filter and by estimating the LP coefficients from the input signal without delay. Simulation results confirmed robustness and stability of the proposed algorithm

A high performance hearing aid system with fully programmable ultra low power DSP

This paper presents the design of fully programmable digital signal processor for the hearing aid system and optimized implementation of digital hearing aid algorithms. The average performance of the developed processor is measured by performing Fast Fourier Transform (FFT) algorithm. The proposed applications such as variable multiband loudness compensation algorithm with wide dynamic range compression and sub-band based adaptive feedback cancellation algorithm are optimized for real-time processing by exploiting the data and instruction parallelism of the developed processor. The results show that the computational ability and power consumption of the developed processor are suitable to use for the hearing aid system. The optimization achieves that the computational time to perform the full applications on the processor takes only under 40% of the constraint for real-time processing.

Robust noise PSD estimation for binaural hearing aids in time-varying diffuse noise field

In this paper, we present an unsupervised noise PSD estimation algorithm for binaural hearing aids in a time-varying diffuse noise field. It is shown that the noise PSD can be obtained from the eigenvalues of the input covariance matrix together with the noise coherence function effective at low frequencies. To reduce the estimation bias due to fast smoothing, pre- and post-compensation methods are proposed. The proposed algorithm is able to track non-stationary noise PSD without tracking delay or underestimation problems. Its performance is independent of the target speech direction and input SNR. Results of the objective parameter evaluation demonstrate the superiority of the proposed algorithm over conventional techniques.

Study on self hearing assessment using speech sounds

In this study, we proposed new self assessment of hearing loss in mobile phones and realized a function of compensation for hearing impaired person. The results of experiments on mobile phone showed that the proposed hearing test is sufficient to check hearing loss and the compensation based on the result of the proposed hearing test can improve speech intelligibility of hearing impaired persons.

Noise reduction for binaural hearing aids using unsupervised diffuse noise estimator

In this paper a new noise reduction algorithm for binaural hearing aids is proposed. This algorithm is capable of suppressing both nonstationary diffuse noise and unknown directional interferences without distorting the directional cues. For the estimation of the diffuse noise power spectral density (PSD), we utilize the eigenstructure of the 2×2 input covariance matrix, together with a compensation process for preventing the underestimation at low frequencies. The interference PSD is estimated from the target cancelled input signals through the signal prediction. Effectiveness of the proposed algorithm was confirmed according to the computer simulations in terms of noise reduction and binaural cue preservation.

The Band-Importance Function for the Korean Standard Sentence Lists for Adults

Background and Objectives The band-importance function (BIF) refers to a value characterizing the relative importance of different frequencies to speech intelligibility. The purpose of this study was to derive the BIF for the Korean standard sentence lists for adults (KS-SL-A). Subjects and Methods In this study, sentences from the KS-SL-A were used as the speech material. Twenty-six normal-hearing Korean listeners participated and intelligibility scores in 8 filters with 3 signal-to-noise ratio conditions were obtained. Based on the intelligibility score percentages, the BIF for the KS-SL-A was derived by using an established protocol. Results Band-importance weights varied across frequency bands. The most important frequency region was around 316 Hz (20.0%), and the importance of the frequency bands below the center frequency (CF) of 1,778 Hz was 59.6%. Therefore, low frequencies below the CF of 1,778 Hz were more important than high frequencies above the CF of 1,778 Hz. Conclusions The BIF for KS-SL-A could be applied towards developing a hearing aid fitting formulae for Korean listeners.

Smartphone-based self hearing assessment using phonemes

Phonemes provide an interesting alternative to pure tones in hearing tests. We propose a new smartphone-based method for self hearing assessment using the four Korean phonemes which are similar to the English phonemes /a/,/i/,/sh/, and/s/, respectively. We conducted tests on 15 subjects diagnosed with mild to severe hearing loss and estimated their conventional pure tone hearing thresholds from their phoneme hearing thresholds using regression analysis. The phoneme-based self hearing assessment (PhoSHA) was found to be sufficiently reliable in estimating the hearing thresholds of hearing-impaired subjects. The difference between the hearing thresholds obtained through conventional pure tone audiometry and those obtained using our method was 5.6 dB HL on average. The proposed hearing assessment was able to significantly reduce the mean test time compared to conventional pure tone audiometry.