Speech perception in various acoustic environments: Comparison of different sound coding strategies

Objectives to compare speech perception in a quiet and noisy environment using a basic audio coding strategy (CIS) and a modern strategy (ACE) over a period of 24 months. Material and methods. The study involved 30 patients who received hearing rehabilitation in the National Medical Research Center for Otorhinolaryngology of the Federal Medico-Biological Agency in the period of 2018 2021. The inclusion criteria were: implantation in the adult age (from 18 to 45 years), speaking fluent Russian, hearing loss after speech skills formation. After initialization and programming of the speech processor, the patients underwent speech audiometry in a free sound field using syllabic and speech tables in silence and noise. The results were collected in the special MS Excel templates and subjected to statistical analysis. Results. The intelligibility of syllables in patients with CIS and ACE strategies took comparable values and grew with experience within 24 months (from 52 7.00% at the beginning of the study to 72 7.25% at the end), the greatest increase in intelligibility was noted in the first 3 months after connecting the speech processor (from 52 7.00% to 66 7.87%). Using the Greenberg speech table in silence, the groups with the CIS strategy and the ACE strategy obtained similar results with a slight advantage of the ACE strategy up to 6 months of the study. Later, a significantly higher increase in speech perception was observed in the group with the ACE strategy compared to the group with CIS. After 12 months, the perception tests showed 67 8.62% in patients with CIS strategy and 71 7.54% in patients with ACE, after 24 months the results were 68 9.12%, and 72 8.62% respectively. Under noise conditions, we observed an increase of the difference between groups starting from 6 months (41 5.33% in patients with CIS versus 43.3 7.55% with ACE), the largest difference was registered after 24 months (51 5.50% versus 57 8.25% respectively). Conclusion. When compared to the basic strategy, a modern sound coding strategy with a higher resolution can improve speech perception especially with complex speech patterns and in a noisy environment.

An End-to-End Deep Learning Sound Coding Strategy for Cochlear Implants

Cochlear implant (CI) users struggle to understand speech in noisy conditions. In this work, we propose an end-to-end speech coding and denoising sound coding strategy that estimates the electrodograms from the raw audio captured by the microphone. We compared this approach to a classic Wiener filter and TasNet to assess its potential benefits in the context of electric hearing. The performance of the network is assessed by means of noise reduction performance (signal-to-noise-ratio improvement) and objective speech intelligibility measures. Furthermore, speech intelligibility was measured in 5 CI users to assess the potential benefits of each of the investigated algorithms. Results suggest that the speech performance of the tested group seemed to be equally good using our method compared to the front-end speech enhancement algorithm.

Comparison of sound perception using CIS and ACE sound coding strategies in cochlear implants

Objectives to study the effect of ACE and CIS sound coding strategies on sound perception in patients with the cochlear implants system produced by Cochlear Limited. Material and methods. The study included 50 patients taking the rehabilitation course in the Astrakhan branch of the National Medical Research Center for Otorhinolaryngology of the Federal Medico-Biological Agency over the past 5 years (from 2014 to 2019). The group of subjects included children over 7 years old and adults, whose success in rehabilitation made it possible to perform a full range of tests. The patients underwent tonal threshold audiometry and speech audiometry in a free sound field; the results obtained were registered in special MS Excel tables and further analysed using statistical methods. Results. There were no statistically significant differences in hearing thresholds on tonal audiometry when using the coding strategies ACE and CIS, however, differences in speech perception were observed on average by 4.2%. The patients experienced in using hearing aids reported improved speech recognition, with scores varying within 5%. Conclusion. Using a higher-resolution coding strategy can significantly improve speech recognition, while lower-resolution coding is beneficial for patients with digital hearing aid experience.

3D Sound Coding Color for the Visually Impaired

Contemporary art is evolving beyond simply looking at works, and the development of various sensory technologies has had a great influence on culture and art. Accordingly, opportunities for the visually impaired to appreciate visual artworks through various senses such as auditory and tactile senses are expanding. However, insufficient sound expression and lack of portability make it less understandable and accessible. This paper attempts to convey a color and depth coding scheme to the visually impaired, based on alternative sensory modalities, such as hearing (by encoding the color and depth information with 3D sounds of audio description) and touch (to be used for interface-triggering information such as color and depth). The proposed color-coding scheme represents light, saturated, and dark colors for red, orange, yellow, yellow-green, green, blue-green, blue, and purple. The paper’s proposed system can be used for both mobile platforms and 2.5D (relief) models.

A sound coding strategy based on a temporal masking model for cochlear implants

Auditory masking occurs when one sound is perceptually altered by the presence of another sound. Auditory masking in the frequency domain is known as simultaneous masking and in the time domain is known as temporal masking or non-simultaneous masking. This works presents a sound coding strategy that incorporates a temporal masking model to select the most relevant channels for stimulation in a cochlear implant (CI). A previous version of the strategy, termed psychoacoustic advanced combination encoder (PACE), only used a simultaneous masking model for the same purpose, for this reason the new strategy has been termed temporal-PACE (TPACE). We hypothesized that a sound coding strategy that focuses on stimulating the auditory nerve with pulses that are as masked as possible can improve speech intelligibility for CI users. The temporal masking model used within TPACE attenuates the simultaneous masking thresholds estimated by PACE over time. The attenuation is designed to fall exponentially with a strength determined by a single parameter, the temporal masking half-life T½. This parameter gives the time interval at which the simultaneous masking threshold is halved. The study group consisted of 24 postlingually deaf subjects with a minimum of six months experience after CI activation. A crossover design was used to compare four variants of the new temporal masking strategy TPACE (T½ ranging between 0.4 and 1.1 ms) with respect to the clinical MP3000 strategy, a commercial implementation of the PACE strategy, in two prospective, within-subject, repeated-measure experiments. The outcome measure was speech intelligibility in noise at 15 to 5 dB SNR. In two consecutive experiments, the TPACE with T½ of 0.5 ms obtained a speech performance increase of 11% and 10% with respect to the MP3000 (T½ = 0 ms), respectively. The improved speech test scores correlated with the clinical performance of the subjects: CI users with above-average outcome in their routine speech tests showed higher benefit with TPACE. It seems that the consideration of short-acting temporal masking can improve speech intelligibility in CI users. The half-live with the highest average speech perception benefit (0.5 ms) corresponds to time scales that are typical for neuronal refractory behavior.