Sangmin Lee

Enhanced beam-steering-based diagonal beamforming algorithm for binaural hearing support devices.

In order to improve speech intelligibility for hearing-impaired people in various listening situations, it is necessary to diversify the possible focusing directions of a beamformer. In a previous report, the concept of binaural beam-steering that can focus a beamformer in diagonal directions was applied to a binaural hearing aid; however, in the previously proposed protocol, the effective frequency range for consistent diagonal beam-steering was limited to the 200-750 Hz range, which is far narrower than that of normal speech signals (200-4000 Hz). In this study, we proposed a modified binaural diagonal beam-steering technique that can reduce the focusing-direction deviations at high input frequencies up to 4000 Hz by introducing a new correction factor to the original protocol that can reduce the differences in gradient between the signal and the noise components at frequencies up to 4000 Hz. In simulation tests, the focusing effect of the proposed algorithm was more consistent than conventional algorithms. The deviations between the target and the focusing directions were reduced 27% in the left device and 6% in the right device with 45° steering at a 4000 Hz input signal, and were reduced 3% in the left device and 25% in the right device with 135° steering. On the basis of the experimental results, we believe that the proposed algorithm has the potential to help hearing-impaired people in various listening situations.

Clinical evaluation of the performance of a blind source separation algorithm combining beamforming and independent component analysis in hearing aid use

There have been several reports on improved blind source separation algorithms that combine beamforming and independent component analysis. However, none of the prior reports verified the clinical efficacy of such combinational algorithms in real hearing aid situations. In the current study, we evaluated the clinical efficacy of such a combinational algorithm using the mean opinion score and speech recognition threshold tests in various types of real-world hearing aid situations involving environmental noise. Parameters of the testing algorithm were adjusted to match the geometric specifications of the real behind-the-ear type hearing aid housing. The study included 15 normal-hearing volunteers and 15 hearing-impaired patients. Experimental results demonstrated that the testing algorithm improved the speech intelligibility of all of the participants in noisy environments, and the clinical efficacy of the combinational algorithm was superior to either the beamforming or independent component analysis algorithms alone. Despite the computational complexity of the testing algorithm, our experimental results and the rapid enhancement of hardware technology indicate that the testing algorithm has the potential to be applied to real hearing aids in the near future, thereby improving the speech intelligibility of hearing-impaired patients in noisy environments.

Enhancement of speech/music decision employing GMM for SMV codec

In this paper, we propose a novel approach to improve the performance of speech/music classification for the selectable mode vocoder (SMV) of 3GPP2 using the Gaussian mixture model (GMM) with a minimum classification error (MCE) method. Also, to enhance We first present an effective analysis of the features and the classification method adopted in the conventional SMV. And then feature vectors which are applied to the GMM are selected from relevant parameters of the SMV for the efficient speech/music classification. The performance of the proposed algorithm is evaluated under various conditions and yields better results compared with the conventional scheme of the SMV.

Effect of a Bluetooth-Implemented Hearing Aid on Speech Recognition Performance Subjective and Objective Measurement

Objectives: The object was to evaluate speech perception improvement through Bluetooth-implemented hearing aids in hearing-impaired adults. Methods: Thirty subjects with bilateral symmetric moderate sensorineural hearing loss participated in this study. A Bluetooth-implemented hearing aid was fitted unilaterally in all study subjects. Objective speech recognition score and subjective satisfaction were measured with a Bluetooth-implemented hearing aid to replace the acoustic connection from either a cellular phone or a loudspeaker system. In each system, participants were assigned to 4 conditions: wireless speech signal transmission into hearing aid (wireless mode) in quiet or noisy environment and conventional speech signal transmission using external microphone of hearing aid (conventional mode) in quiet or noisy environment. Also, participants completed questionnaires to investigate subjective satisfaction. Results: Both cellular phone and loudspeaker system situation, participants showed improvements in sentence and word recognition scores with wireless mode compared to conventional mode in both quiet and noise conditions (P < .001). Participants also reported subjective improvements, including better sound quality, less noise interference, and better accuracy naturalness, when using the wireless mode (P < .001). Conclusions: Bluetooth-implemented hearing aids helped to improve subjective and objective speech recognition performances in quiet and noisy environments during the use of electronic audio devices.

A study for the effect of widened auditory filter of hearing impaired listener

The reduced frequency selectivity is a typical phenomenon of sensorineural hearing loss. In this paper, we made modeling of reduced frequency selectivity for hearing impaired listener. The model of reduced frequency selectivity was generated with bandwidth control algorithm based on ERB(equivalent rectangular bandwidth) of auditory filter. In other to examine the effectiveness of model, we compared PESQ(perceptual evaluation of speech quality) score and LLR(log likelihood ratio) score with 36 Korean worlds of two syllables. To verify the effect on noise condition, we mixed white and babble noise with 0dB and -3dB SNR to speech words. As the result, PESQ score is lower as extending bandwidth of filter however LLR score is almost same. It means that non-linearity and widen auditory filter characteristics caused by reduced frequency selectivity could be reflected in bandwidth control algorithm.

A method to reduce steps and time of hearing test on individual device

It took a lot of time to test the hearing loss, and old people were difficulty in having a concentration for a long time. The purpose of this study is to setup a fast self-test of finding the hearing level. We suggested two ideas to reduce time and steps. First, we expected the first sound using an average and an extended scope of levels. Second, the test of unnecessary frequency was skipped. We assume that the hearing level of the normal was similar to other frequencies or existed in regular range. A pure tone was generated from device based on the expectation of hearing level. If the hearing level of subject was under 30dB, test in some frequencies could be skipped. It is able to save the whole time as reducing steps in each frequency.