Speech Intelligibility In Background Noise Research Articles

Perceptual Evaluation of Binaural MVDR-Based Algorithms to Preserve the Interaural Coherence of Diffuse Noise Fields.

Besides improving speech intelligibility in background noise, another important objective of noise reduction algorithms for binaural hearing devices is preserving the spatial impression for the listener. In this study, we evaluate the performance of several recently proposed noise reduction algorithms based on the binaural minimum-variance-distortionless-response (MVDR) beamformer, which trade-off between noise reduction performance and preservation of the interaural coherence (IC) for diffuse noise fields. Aiming at a perceptually optimized result, this trade-off is determined based on the IC discrimination ability of the human auditory system. The algorithms are evaluated with normal-hearing participants for an anechoic scenario and a reverberant cafeteria scenario, in terms of both speech intelligibility using a matrix sentence test and spatial quality using a MUlti Stimulus test with Hidden Reference and Anchor (MUSHRA). The results show that all the binaural noise reduction algorithms are able to improve speech intelligibility compared with the unprocessed microphone signals, where partially preserving the IC of the diffuse noise field leads to a significant improvement in perceived spatial quality compared with the binaural MVDR beamformer while hardly affecting speech intelligibility.

Speech Perception in Noise With Formant Enhancement for Older Listeners

Purpose Degraded speech intelligibility in background noise is a common complaint of listeners with hearing loss. The purpose of the current study is to explore whether 2nd formant (F2) enhancement improves speech perception in noise for older listeners with hearing impairment (HI) and normal hearing (NH). Method Target words (e.g., color and digit) were selected and presented based on the paradigm of the coordinate response measure corpus. Speech recognition thresholds with original and F2-enhanced speech in 2- and 6-talker babble were examined for older listeners with NH and HI. Results The thresholds for both the NH and HI groups improved for enhanced speech signals primarily in 2-talker babble, but not in 6-talker babble. The F2 enhancement benefits did not correlate significantly with listeners' age and their average hearing thresholds in most listening conditions. However, speech intelligibility index values increased significantly with F2 enhancement in babble for listeners with HI, but not for NH listeners. Conclusions Speech sounds with F2 enhancement may improve listeners' speech perception in 2-talker babble, possibly due to a greater amount of speech information available in temporally modulated noise or a better capacity to separate speech signals from background babble.

Audiomotor Perceptual Training Enhances Speech Intelligibility in Background Noise

Sensory and motor skills can be improved with training, but learning is often restricted to practice stimuli. As an exception, training on closed-loop (CL) sensorimotor interfaces, such as action video games and musical instruments, can impart a broad spectrum of perceptual benefits. Here we ask whether computerized CL auditory training can enhance speech understanding in levels of background noise that approximate a crowded restaurant. Elderly hearing-impaired subjects trained for 8weeks on a CL game that, like a musical instrument, challenged them to monitor subtle deviations between predicted and actual auditory feedback as they moved their fingertip through a virtual soundscape. We performed our study as a randomized, double-blind, placebo-controlled trial by training other subjects in an auditory working-memory (WM) task. Subjects in both groups improved at their respective auditory tasks and reported comparable expectations for improved speech processing, thereby controlling for placebo effects. Whereas speech intelligibility was unchanged after WM training, subjects in the CL training group could correctly identify 25% more words in spoken sentences or digit sequences presented in high levels of background noise. Numerically, CL audiomotor training provided more than three times the benefit of our subjects' hearing aids for speech processing in noisy listening conditions. Gains in speech intelligibility could be predicted from gameplay accuracy and baseline inhibitory control. However, benefits did not persist in the absence of continuing practice. These studies employ stringent clinical standards to demonstrate that perceptual learning on a computerized audio game can transfer to "real-world" communication challenges.

Speech intelligibility improvement in noisy environments based on energy correlation in frequency bands

A new speech processing algorithm is proposed to improve speech intelligibility in noisy environments without increasing speech energy. The method improves the near-end speech intelligibility by optimizing the frame-based spectral energy correlation between clean speech and noisy modified speech with a power constraint. This algorithm is developed based on short-time objective intelligibility (STOI) measure, which predicts speech intelligibility in background noise according to the correlation of clean and noisy speeches. The proposed method is compared with unprocessed speech and two baseline methods using two objective intelligibility measures and an intelligibility listening test under various noisy conditions. Results show large intelligibility improvements with the proposed method over the unprocessed noisy speech. In addition, compared with the baseline methods, the proposed algorithm provides the best intelligibility scores for all noisy conditions in the STOI measure and for low signal-to-noise ratios in the speech intelligibility index. The word recognition results also show that the proposed algorithm performs better than the unprocessed speech and the reference methods. An objective quality measure is applied to investigate the speech quality of the introduced method, which is proven to insignificantly affect speech quality.

Target-word identification in noise with formant enhancement for hearing-impaired listeners

Degraded speech intelligibility in background noise is a common complaint of most listeners with hearing loss. The purpose of the current study is to investigate the effect of spectral enhancement of F2 on target-word identification in noise for the old listeners with hearing loss (HL) and with normal hearing (NH). Target words (e.g., name, color, and digit) were selected and presented based on the paradigm of coordinate response measure (CRM) corpus of English and Chinese versions. Identification tasks with original and F2-enhanced speech in the 2-talker and 6-talker babbles were designed for the two groups (HL and NH). Thresholds of word identification was measured by using adaptive up-down methods. Results showed that listeners with NH had better performance on word identification in noise than listeners with HL in almost all listening conditions. More importantly, thresholds of both groups were improved for enhanced speech signals. Compared with NH group, listeners with HL gained significantly greater benefits in the most challenging condition. These preliminary results suggested that speech sounds with F2 enhancement might improve listeners’ ordinary speech perception in noise.

Minimal Hearing Loss: Implications and Management Options for Educational Settings

Audibility, which refers to the ability of sound to be heard, is not sufficient for listening and learning environments, such as school classrooms. Speech intelligibility, not audibility, is the key to understanding and, therefore, must be addressed for all children, especially those who have some amount of hearing loss. It is well documented that children's central auditory systems are not fully myelinated or mature until the age of 10 to 12 years (Moore, 2002; Musiek, Gollegly, & Baran, 1984). School-age children have “developing” auditory systems due to their poorer sensitivity (when compared to adults) to small acoustic cues in speech, such as voice-onset time and formant-frequency transition (Elliott, 1986; Elliott, Longinotti, Meyer, Raz, & Zucker, 1981). Children are also less able to selectively attend to auditory tasks, have difficulty recognizing speech distorted by reverberation, and have problems with speech intelligibility in background noise and reverberation plus noise (Finitzo-Hieber & Tillman, 1978; Neuman & Hochberg, 1983; Stuart, 2005). Therefore, children under the age of 13 years (i.e., those in elementary and middle school) have been described as “special listeners” (Nabelek & Nabelek, 1994). This article describes minimal hearing loss (MHL), the poor acoustics found in educational environments, and the impact of those acoustics on children with MHL. In addition, this article reviews environmental modifications that can be made to improve classroom acoustics. This article offers multiple researchers' strategies for better access to listening and learning, including soundfield amplification options for improving the signal-to-noise ratio in classroom settings.

Improving word recognition in noise among hearing-impaired subjects with a single-channel cochlear noise-reduction algorithm

A common complaint of the hearing impaired is the inability to understand speech in noisy environments even with their hearing assistive devices. Only a few single-channel algorithms have significantly improved speech intelligibility in noise for hearing-impaired listeners. The current study introduces a cochlear noise reduction algorithm. It is based on a cochlear representation of acoustic signals and real-time derivation of a binary speech mask. The contribution of the algorithm for enhancing word recognition in noise was evaluated on a group of 42 normal-hearing subjects, 35 hearing-aid users, 8 cochlear implant recipients, and 14 participants with bimodal devices. Recognition scores of Hebrew monosyllabic words embedded in Gaussian noise at several signal-to-noise ratios (SNRs) were obtained with processed and unprocessed signals. The algorithm was not effective among the normal-hearing participants. However, it yielded a significant improvement in some of the hearing-impaired subjects under different listening conditions. Its most impressive benefit appeared among cochlear implant recipients. More than 20% improvement in recognition score of noisy words was obtained by 12, 16, and 26 hearing-impaired at SNR of 30, 24, and 18 dB, respectively. The algorithm has a potential to improve speech intelligibility in background noise, yet further research is required to improve its performances.

Joint Time–Frequency Segmentation Algorithm for Transient Speech Decomposition and Speech Enhancement

We develop an algorithm, the joint time-frequency segmentation algorithm, where the wavelet packet coefficients of the analyzed speech signal are represented as tiles of a time-frequency representation adapted to the characteristics of the signal itself. Further, our algorithm enables the decomposition of the speech signal into transient and non-transient components, respectively. Any block of wavelet packet coefficients, whose tiling height is larger than or equal to the tiling width belongs to the transient component and vice versa for the non-transient component. The transient component is selectively amplified and recombined with the original speech to generate the modified speech with energy adjusted to be equal to the original speech. The intelligibility of the original and modified speech is evaluated by 16 human listeners. Word recognition rate results show that the modified speech significantly improves speech intelligibility in background noise, i.e., by 10% absolute at 0 dB to 27% absolute at -30 dB.

The effects of fundamental frequency contour manipulations on speech intelligibility in background noise

Previous studies have documented that speech with flattened or inverted fundamental frequency (F0) contours is less intelligible than speech with natural variations in F0. The purpose of this present study was to further investigate how F0 manipulations affect speech intelligibility in background noise. Speech recognition in noise was measured for sentences having the following F0 contours: unmodified, flattened at the median, natural but exaggerated, inverted, and sinusoidally frequency modulated at rates of 2.5 and 5.0 Hz, rates shown to make vowels more perceptually salient in background noise. Five talkers produced 180 stimulus sentences, with 30 unique sentences per F0 contour condition. Flattening or exaggerating the F0 contour reduced key word recognition performance by 13% relative to the naturally produced speech. Inverting or sinusoidally frequency modulating the F0 contour reduced performance by 23% relative to typically produced speech. These results support the notion that linguistically incorrect or misleading cues have a greater deleterious effect on speech understanding than linguistically neutral cues.

Speech intelligibility in background noise with ideal binary time-frequency masking

Ideal binary time-frequency masking is a signal separation technique that retains mixture energy in time-frequency units where local signal-to-noise ratio exceeds a certain threshold and rejects mixture energy in other time-frequency units. Two experiments were designed to assess the effects of ideal binary masking on speech intelligibility of both normal-hearing (NH) and hearing-impaired (HI) listeners in different kinds of background interference. The results from Experiment 1 demonstrate that ideal binary masking leads to substantial reductions in speech-reception threshold for both NH and HI listeners, and the reduction is greater in a cafeteria background than in a speech-shaped noise. Furthermore, listeners with hearing loss benefit more than listeners with normal hearing, particularly for cafeteria noise, and ideal masking nearly equalizes the speech intelligibility performances of NH and HI listeners in noisy backgrounds. The results from Experiment 2 suggest that ideal binary masking in the low-frequency range yields larger intelligibility improvements than in the high-frequency range, especially for listeners with hearing loss. The findings from the two experiments have major implications for understanding speech perception in noise, computational auditory scene analysis, speech enhancement, and hearing aid design.

Improving Speech Intelligibility in Background Noise with an Adaptive Directional Microphone

Omnidirectional, supercardioid, and adaptive directional microphones (ADM) were evaluated in combination with the ADRO amplification scheme for eight participants with moderate sloping hearing losses. The ADM produced better speech perception scores than the other two microphones in all noise conditions. Participants performed the Hearing in Noise Test sentences at -4.5 dB SNR or better, which is similar to the level achievable with normal hearing. The Speech, Spatial and Qualities of Hearing Scale indicated no disadvantages of using the ADM relative to the omnidirectional microphone in real-life situations. The ADM was preferred over the omnidirectional microphone in 54% of situations, compared to 17% preferences for the omnidirectional microphone, and 29% no preference. The combination of the ADM to improve SNR, and ADRO to keep the signal output comfortable and audible provided near-normal hearing performance for people with moderate hearing loss. The ADM is the recommended microphone configuration for ADRO hearing aids.

Evaluation of phoneme compression schemes designed to compensate for temporal and spectral masking in background noise

The effect of phonemic compression has been studied on speech intelligibility in background noise in hearing-impaired listeners with moderate-to-severe high-frequency losses. One configuration, anti-upward-spread-of-masking (anti-USOM) focuses on a release from spectral masking of high-frequency speech cues by selective spectral tilting. Release from temporal masking is the main goal of a second configuration, high-pass filtered compression (HFC), which reduces the speech modulations within a high-pass filtered compression channel. Speech intelligibility was measured with consonant-vowel-consonant (CVC) words in a multi-talker babble and a single-talker background noise. Anti-USOM has a significant negative effect on the phoneme scores in background noise. HFC compression tends to improve vowel intelligibility in a single-talker background noise, especially for the listeners with a relatively poor speech score. In a multi-talker babble noise the effects of HFC compression tend to be negative. It can be concluded that no significant release from spectral or temporal masking is obtained by the applied processing.SumarioEl efecto de la compresión fonémica ha sido estudiado en la inteligibilidad del lenguaje con ruido de fondo, en hipoacúsicos con pérdidas entre moderadas y severas en frecuencias agudas. Una configuración (anti USOM) esta centrada en la liberación del espectro enmascarante de claves lingüísticas de alta frecuencia por medio de un espectro selectivamente inclinado. La liberación del enmascaramiento temporal es el objetivo principal de la segunda configuración (HFC) que reduce las modulaciones del lenguaje en un canal de compresión de filtros de altas frecuencias. La inteligibilidad del lenguaje fue medida con palabras Consonante-Vocal-Consonante (CVC) en un fondo de ruido de hablantes múltiples y de hablante aislado. El Anti-USOM tuvo un efecto significativamente negativo en las puntuaciones de los fonemas con ruido de fondo. La compresión HFC tiende a mejorar la inteligibilidad de las vocales con ruido de fondo de hablante aislado, especialmente para personas con puntuaciones de lenguaje relativamente pobre. Con ruido de hablantes múltiples los efectos de la compresión HFC tienden a ser negativos. Se puede concluir que no se obtiene una liberación significativa a partir del enmascaramiento espectral o temporal con el procesamiento que se aplicó.

Speech Discrimination in Background Noise with the Vibrant® Soundbridge™ Middle Ear Implant

Objective: Evaluate speech intelligibility in competing background noise for monaural users of the Vibrant^® Soundbridge™ (VSB) middle ear implant (Symphonix). Patients and Material: Nine adults with moderate to severe bilateral sensorineural hearing loss, and implanted with a unilateral VSB, were included in the study. The patients’ experience of the implant ranged from 9 to 24 months. Retrospective single-subject repeated measures of speech intelligibility in background noise were performed using 2 different test procedures, the Elbaz test and the Garin and Galle test. The patients were tested VSB aided and VSB unaided in a variety of signal-to-noise ratios. The correct-score percentage for each ratio for each condition was averaged for the group of patients and compared with normative data for each test method. Results: The VSB-aided condition showed results approaching normative data for both test methods. At a signal-to-noise ratio of zero, the Elbaz test showed a mean correct score of 55% for the VSB-unaided condition versus 85% for the VSB-aided condition. The Garin and Galle test showed a mean score of 34% for the VSB-unaided condition versus 94% for the VSB-aided condition. Conclusions: Although the unilateral VSB middle ear implant does not restore stereophony, it does improve speech intelligibility in background noise.