Speech perception in noise: Impact of directional microphones in users of combined electric-acoustic stimulation

Enhancing Cochlear Implant Outcomes across Age Groups: The Interplay of Forward Focus and Advanced Combination Encoder Coding Strategies in Noisy Conditions

Background: Hearing in noise is challenging for cochlear implant users and requires significant listening effort. This study investigated the influence of ForwardFocus and number of maxima of the Advanced Combination Encoder (ACE) strategy, as well as age, on speech recognition threshold and listening effort in noise. Methods: A total of 33 cochlear implant recipients were included (age ≤ 40 years: n = 15, >40 years: n = 18). The Oldenburg Sentence Test was used to measure 50% speech recognition thresholds (SRT50) in fluctuating and stationary noise. Speech was presented frontally, while three frontal or rear noise sources were used, and the number of ACE maxima varied between 8 and 12. Results: ForwardFocus significantly improved the SRT50 when noise was presented from the back, independent of subject age. The use of 12 maxima further improved the SRT50 when ForwardFocus was activated and when noise and speech were presented frontally. Listening effort was significantly worse in the older age group compared to the younger age group and was reduced by ForwardFocus but not by increasing the number of ACE maxima. Conclusion: Forward Focus can improve speech recognition in noisy environments and reduce listening effort, especially in older cochlear implant users.

Speech comprehension in noise-considerations for ecologically valid assessment of communication skills ability with cochlear implants

BACKGROUND

Nowadays, cochlear implant (CI) patients mostly show good to very good speech comprehension in quiet, but there are known problems with communication in everyday noisy situations. There is thus a need for ecologically valid measurements of speech comprehension in real-life listening situations for hearing-impaired patients. The additional methodological effort must be balanced with clinical human and spatial resources. This study investigates possible simplifications of a complex measurement setup.

METHODS

The study included 20 adults from long-term follow-up after CI fitting with postlingual onset of hearing impairment. The complexity of the investigated listening situations was influenced by changing the spatiality of the noise sources and the temporal characteristics of the noise. To compare different measurement setups, speech reception thresholds (SRT) were measured unilaterally with different CI processors and settings. Ten normal-hearing subjects served as reference.

RESULTS

In a complex listening situation with four loudspeakers, differences in SRT from CI subjects to the control group of up to 8 dB were found. For CI subjects, this SRT correlated with the situation with frontal speech signal and fluctuating interference signal from the side with R2 = 0.69. For conditions with stationary interfering signals, R2 values <0.2 were found.

CONCLUSION

There is no universal solution for all audiometric questions with respect to the spatiality and temporal characteristics of noise sources. In the investigated context, simplification of the complex spatial audiometric setting while using fluctuating competing signals was possible.

[Speech comprehension in noise-considerations for ecologically valid assessment of communication skills ability with cochlear implants. German version]

BACKGROUND

Nowadays, cochlear implant (CI) patients mostly show good to very good speech comprehension in quiet, but there are known problems with communication in everyday noisy situations. There is thus a need for ecologically valid measurements of speech comprehension in real-life listening situations for hearing-impaired patients. The additional methodological effort must be balanced with clinical human and spatial resources. This study investigates possible simplifications of a complex measurement setup.

METHODS

The study included 20 adults from long-term follow-up after CI fitting with postlingual onset of hearing impairment. The complexity of the investigated listening situations was influenced by changing the spatiality of the noise sources and the temporal characteristics of the noise. To compare different measurement setups, speech reception thresholds (SRT) were measured unilaterally with different CI processors and settings. Ten normal-hearing subjects served as reference.

RESULTS

In a complex listening situation with four loudspeakers, differences in SRT from CI subjects to the control group of up to 8 dB were found. For CI subjects, this SRT correlated with the situation with frontal speech signal and fluctuating interference signal from the side with R2 = 0.69. For conditions with stationary interfering signals, R2 values <0.2 were found.

CONCLUSION

There is no universal solution for all audiometric questions with respect to the spatiality and temporal characteristics of noise sources. In the investigated context, simplification of the complex spatial audiometric setting while using fluctuating competing signals was possible.

Signal processing & audio processors

Signal processing algorithms are the hidden components in the audio processor that converts the received acoustic signal into electrical impulses while maintaining as much relevant information as possible. Signal processing algorithms should be smart enough to mimic the functionality of external, middle and the inner-ear to provide the cochlear implant (CI) user with a hearing experience as natural as possible. Modern sound processing strategies are based on the continuous interleaved sampling (CIS) strategy proposed by B. Wilson in 1991, which provided envelope information over several intracochlear electrodes. The CIS strategy brought significant gains in speech perception. Translational research activities of MED-EL resulted in further improvements in speech understanding in noisy environments as well as enjoyment of music by not only coding CIS-based envelope information, but by also representing temporal fine structure information in the stimulation patterns of the apical channels. Further developments include "complete cochlear coverage" made possible by deep insertion of the intracochlear electrode, elaborate front end processing, anatomy based fitting (ABF), triphasic pulse stimulation instrumental in the suppression of facial nerve stimulation, and bimodal delay compensation allowing unilateral CI users to experience hearing with hearing aids on the contralateral ear. The large number of hardware developments might be exemplified by the RONDO, the world's first single unit audio processor in 2013. This article covers the milestones of translational research around the signal processing and audio processor topic that took place in association with MED-EL.

Activating a Noise-Gating Algorithm and Personalizing Electrode Threshold Levels Improve Recognition of Soft Speech for Adults With CIs

OBJECTIVE

In contrast to the moderate presentation levels most commonly used in clinical practice, speech encountered in everyday life often occurs at low levels, such as when a conversational partner whispers or speaks from another room. In addition, even when the overall signal level is moderate, levels for particular words or speech sounds, such as voiceless consonants, can be considerably lower. Existing techniques for improving recognition of low-level speech for cochlear implant users include using a wider input dynamic range and elevating electrode threshold levels (T-levels). While these techniques tend to positively impact recognition of soft speech, each has also been associated with drawbacks. Recently, a noise-gating (NG) algorithm was reported, which works by eliminating input to an electrode when signal level in the associated frequency channel is at or below a predetermined threshold. Available evidence suggests that activation of this algorithm can improve recognition of sentences presented at low levels (35 to 50 dB SPL), though it remains unclear whether the benefits will be equally evident with both manufacturer default and individually optimized T-levels. The primary aim of this study was therefore to evaluate the independent and combined effects of NG activation and T-level personalization.

METHODS

Twenty adults between the ages of 25 and 77 years (M = 54.9 years, SD = 17.56) with postlingually acquired profound hearing loss completed testing for this study. Participants were fit with an Advanced Bionics Naida CI Q90 speech processor, which contained four programs based on each participant's existing everyday program. The programs varied by the NG algorithm setting (on, off) and T-level method (default 10% of M-level, personalized based on subjective ratings of "very quiet"). All participants completed speech sound detection threshold testing (/m/, /u/, /a/, /i/, /s/, and /ʃ/), as well as tests of monosyllabic word recognition in quiet (45 and 60 dB SPL), sentence recognition in quiet (45 and 60 dB SPL), and sentence recognition in noise (45-dB SPL speech, +10 dB SNR).

RESULTS

Findings demonstrated that both activating NG and personalizing T-levels in isolation significantly improved detection (speech sounds) and recognition (monosyllables, sentences in quiet, and sentences in noise) of soft speech, with their respective individual effects being comparable. However, the lowest speech sound detection thresholds and the highest speech recognition performance were identified when NG was activated in conjunction with personalized T-levels. Importantly, neither T-level personalization nor NG activation affected recognition of speech presented at 60 dB SPL, which suggests the strategies should not be expected to interfere with recognition of average conversational speech.

CONCLUSIONS

Taken together, these data support the clinical recommendation of personalizing T-levels and activating NG to improve the detection and recognition of soft speech. However, future work is needed to evaluate potential limitations of these techniques. Specifically, speech recognition testing should be performed in the presence of diverse noise backgrounds and home-trials should be conducted to determine processing effects on sound quality in realistic environments.

Device profile of the MED-EL cochlear implant system for hearing loss: overview of its safety and efficacy

INTRODUCTION

Patients suffering from severe to profound hearing loss or even deafness can achieve a hearing improvement with a cochlear implant (CI) treatment that is significantly higher than the results achieved with conventional hearing aids. The CI system consists of an implantable stimulator, which is inserted retro-auricularly into the mastoid, and an externally worn processor unit, which provides the pickup of sound and processing of acoustic information as well as the power supply for the stimulator and internal current sources. The stimulator has an electrode array that is inserted into the cochlea.

AREAS COVERED

This is a descriptive overview of MED-EL's multichannel CI system (MED-EL, Innsbruck, Austria), which was introduced to the European market in 1994. The continuing development of the implant as well as the external components is outlined and various other aspects (stimulation strategy, adaptation, results, reliability) are discussed.

EXPERT COMMENTARY

The strength of the company is the continuous pursuit of innovative ideas. This is evidenced by numerous innovations. The reliability of the implants has been continuously improved. The current SYNCHRONY models of the manufacturer show no indication of technically caused failures over an observation period of 5 years.