Reduced Speech Intelligibility Research Articles

Effects of early and late reflections on intelligibility of reverberated speech by cochlear implant listeners

The purpose of this study was to determine the overall impact of early and late reflections on the intelligibility of reverberated speech by cochlear implant listeners. Two specific reverberation times were assessed. For each reverberation time, sentences were presented in three different conditions wherein the target signal was filtered through the early, late or entire part of the acoustic impulse response. Results obtained with seven cochlear implant listeners indicated that while early reflections neither enhanced nor reduced overall speech perception performance, late reflections severely reduced speech intelligibility in both reverberant conditions tested.

Communication Support through Multimodal Supplementation:A Scoping Review

Speech supplementation strategies improve spoken communication for people with motor speech disorders who experience reduced speech intelligibility. The purpose of this review was to summarize the literature on traditional supplementation strategies (e.g., alphabet supplementation, topic supplementation, and gestural supplementation) and to expand the definition of speech supplementation to include additional modalities, such as augmenting speech with pictures via mobile technology, and conversation management strategies. Results showed that studies of traditional supplementation consistently reported positive outcomes, including increased intelligibility, decreased speech rate, and positive attitudes toward speakers. New modalities, such as supplementing speech through digital photos, may come to be integrated with traditional approaches, given the proliferation of digital photography and mobile tablet technologies. In addition, new research is exploring the role of communication partners in dyads where one speaker has dysarthria, as well as strategies that communication partners employ to understand dysarthric speech.

A perceptually motivated active noise cancellation system for hearing impaired listeners: An overview

Nowadays most hearing impaired (HI) patients are fitted with either open-fitting or vented-fitting hearing aids (HAs) to reduce the occlusion effect. In an environment where strong low-frequency ambient noise is present, significant noise energy can directly leak into the ear canal bypassing noise reduction algorithms in the HAs and may reduce speech intelligibility and listening comfort for HA users. One way to mitigate such an issue without occluding the ear canal is to implement an active noise cancellation (ANC) system inside the ear canal. Traditional ANC systems are designed to minimize the total sound pressure level in the ear canal. However, this may not necessarily lead to an optimal solution from the perceptual perspective (e.g., loudness may be reduced instead of being minimized as a result). In this paper, a perceptually motivated feedback ANC system is presented: a spectral shaping filter is applied to the residual error signal to minimize the loudness for HI listeners. In addition, implications of the practical constraints introduced by the HAs are discussed based on acoustic simulations and experimental results.

Monkeys are perceptually tuned to facial expressions that exhibit a theta-like speech rhythm

Human speech universally exhibits a 3- to 8-Hz rhythm, corresponding to the rate of syllable production, which is reflected in both the sound envelope and the visual mouth movements. Artificial perturbation of the speech rhythm outside the natural range reduces speech intelligibility, demonstrating a perceptual tuning to this frequency band. One theory posits that the mouth movements at the core of this speech rhythm evolved through modification of ancestral primate facial expressions. Recent evidence shows that one such communicative gesture in macaque monkeys, lip-smacking, has motor parallels with speech in its rhythmicity, its developmental trajectory, and the coordination of vocal tract structures. Whether monkeys also exhibit a perceptual tuning to the natural rhythms of lip-smacking is unknown. To investigate this, we tested rhesus monkeys in a preferential-looking procedure, measuring the time spent looking at each of two side-by-side computer-generated monkey avatars lip-smacking at natural versus sped-up or slowed-down rhythms. Monkeys showed an overall preference for the natural rhythm compared with the perturbed rhythms. This lends behavioral support for the hypothesis that perceptual processes in monkeys are similarly tuned to the natural frequencies of communication signals as they are in humans. Our data provide perceptual evidence for the theory that speech may have evolved from ancestral primate rhythmic facial expressions.

Motor neuron disease: the impact of decreased speech intelligibility on marital communication

Background: The onset of motor neuron disease (MND), a neurodegenerative disease, results in physical and communication disabilities that impinge on an individual’s ability to remain functionally independent. Multiple aspects of the marital relationship are affected by the continuously changing roles and responsibilities. Communication is one of the most constructive ways of dealing with emotions that are elicited by these changes. Method: This study explored the association between the deteriorating speech of persons with MND and couples’ perception of marital communication. Fourteen couples participated in this non-experimental correlational research study. Data were collected over a 12-month period through the administration of objective and subjective measures. Results: Results showed that despite decreased speech intelligibility, the relationship between the deteriorating speech and the couples’ perception of marital communication was not statistically significant. Conclusion: Overall, the results proved that the supposition that communication between couples will invariably deteriorate as a result of progressively reduced speech intelligibility is not necessarily valid. The fundamental importance of effective communication in marriage is highlighted. It is well established that augmentative and alternative communication strategies can preserve the ability to develop and maintain intimate rewarding relationships, even in the face of profound physical disabilities.

Multiple maskers for speech masking in open-plan offices

Sound masking is an effective method to reduce speech intelligibility for reaching acceptable speech privacy in open-plan offices. Speech-like masker is considered as a good choice to reduce speech intelligibility. Using one masker in masking system is the common way so far. In this paper, a new method was proposed, using randomly integrated speech frames (SF) of the speaker as masker. Because SF masker was based on speech of the same speaker, it is a good speech-like masker. We further studied the method of using multiple SF maskers. The performance of this new masking method was evaluated by objective measurement (STOI). The speech masked by one SF masker and multiple SF maskers were compared. Results showed that speech with SF masker could reduce speech intelligibility. Speech with multiple SF maskers led to poorer speech intelligibility than speech with only one SF masker. Masking speech by multiple SF maskers is an effective way to reduce speech intelligibility in open-plan offices. (Acknowledgement: This research was supported by the joint training PhD program of Chinese Academy of Sciences-Fraunhofer, and Fraunhofer Institute of Building Physics in Stuttgart, Germany.)

Assessing speech intelligibility in a group of Egyptian dysarthric patients

EnAbstract Background Improving speech intelligibility in dysarthric patients is considered the primary goal of therapeutic intervention. Aim This study aimed at examining factors affecting speech intelligibility in four Arabic-speaking dysarthric groups using perceptual and instrumental techniques in order to gain a better understanding of the important factors contributing to reduced speech clarity in these patients. Methods and procedures Participants included 30 male Egyptian dysarthric patients (patient group) and 30 male age-matched healthy individuals (control group). The patient group was subdivided–on the basis of the neurological examination and investigation that had been carried out previously at the Neurology Department, Kasr el Aini Hospital–into four subgroups; spastic, ataxic, flaccid, and hypokinetic (having Parkinsonism). Speech samples consisting of spontaneous speech and a standard reading passage (that the participants were asked to repeat after the assessor) were used to obtain the following variables: speech rate (number of words per minute), Speech Intelligibility Score, number of nonintelligible words per minute, dysphonia grade, percent of consonants correct, percent of vowels correct, Nasalance Score, fundamental frequency, jitter, shimmer, harmonic-to-noise ratio, duration of /a/, first and second formant frequency values for three corner vowels /a/, /i/, and /u/, voice onset time of /b/, /t/, /k/, stop gap of /t/, /t/, /d/, /d/, and duration of /s/ and /∫/. The study examined the differences between the healthy control group and the different dysarthric groups for each variable as well as the correlation between speech intelligibility and each variable within each dysarthric subgroup. Outcomes and results The Speech Intelligibility Score was the highest for flaccid dysarthria and the lowest for ataxic. Results revealed significant differences between the control group and each of the patient groups studied for all subjective measures as well as most of the instrumental measures that were included in the study. A significant positive correlation was found between speech rate and speech intelligibility in patients with ataxic and flaccid dysarthria. However, a negative correlation was found between speech rate and speech intelligibility in patients with hypokinetic dysarthria. A significant negative correlation was found between speech intelligibility and jitter, F1 and F2 of /u/, stop gap of /t/, /t/, /d/, and /d/, and /s/ duration in spastic, ataxic, and flaccid groups. In addition, a significant negative correlation was found between shimmer and speech intelligibility in the ataxic group and between Nasalance Score and speech intelligibility in the flaccid group. Conclusion and implications Factors contributing to reduced speech intelligibility vary from one type of dysarthria to the other.

Identification of Articulation Error Patterns Using a Novel Dependence Network

Articulation errors seriously reduce speech intelligibility and the ease of spoken communication. Speech-language pathologists manually identify articulation error patterns based on their clinical experience, which is a time-consuming and expensive process. This study proposes an automatic pronunciation error identification system that uses a novel dependence network (DN) approach. In order to derive a subject's articulatory information, a photo naming task is performed to obtain the subject's speech patterns. Based on clinical knowledge about speech evaluation, a DN scheme was used to model the relationships of a test word, a subject, a speech pattern, and an articulation error pattern. To integrate DN into automatic speech recognition (ASR), a pronunciation confusion network is proposed to model the probability of DN and is then used to guide the search space of the ASR. Further, to increase the accuracy of the ASR, an appropriate threshold based on a histogram of pronunciation errors is selected in order to disregard rare pronunciation errors. Finally, the articulation error patterns were well identified by integrating the likelihoods of the DNs of each phoneme. The results of this study indicate that it is feasible to clinically implement this dynamic network approach to achieve satisfactory performance in articulation evaluation.

Facial‐muscle weakness, speech disorders and dysphagia are common in patients with classic infantile Pompe disease treated with enzyme therapy

Classic infantile Pompe disease is an inherited generalized glycogen storage disorder caused by deficiency of lysosomal acid α-glucosidase. If left untreated, patients die before one year of age. Although enzyme-replacement therapy (ERT) has significantly prolonged lifespan, it has also revealed new aspects of the disease. For up to 11 years, we investigated the frequency and consequences of facial-muscle weakness, speech disorders and dysphagia in long-term survivors. Sequential photographs were used to determine the timing and severity of facial-muscle weakness. Using standardized articulation tests and fibreoptic endoscopic evaluation of swallowing, we investigated speech and swallowing function in a subset of patients. This study included 11 patients with classic infantile Pompe disease. Median age at the start of ERT was 2.4 months (range 0.1-8.3 months), and median age at the end of the study was 4.3 years (range 7.7 months −12.2 years). All patients developed facial-muscle weakness before the age of 15 months. Speech was studied in four patients. Articulation was disordered, with hypernasal resonance and reduced speech intelligibility in all four. Swallowing function was studied in six patients, the most important findings being ineffective swallowing with residues of food (5/6), penetration or aspiration (3/6), and reduced pharyngeal and/or laryngeal sensibility (2/6). We conclude that facial-muscle weakness, speech disorders and dysphagia are common in long-term survivors receiving ERT for classic infantile Pompe disease. To improve speech and reduce the risk for aspiration, early treatment by a speech therapist and regular swallowing assessments are recommended.Electronic supplementary materialThe online version of this article (doi:10.1007/s10545-011-9404-7) contains supplementary material, which is available to authorized users.

On the acoustics of operating rooms.

Designing modern operating rooms to meet al.l design criteria can be a challenge. Creating a sterile, well‐lit, temperature and humidity appropriate environment for medical operations typically takes precedence over the acoustics of the operating room. The sterile, washable operating room surfaces are commonly hard and reflective, offering little sound absorption. These surface finishes result in strong discrete reflections, increased background noise, and reduced speech intelligibility. Code mandated energy efficiency and ventilation requirements coupled with the owner‐driven desire for economical mechanical systems can result in excessive HVAC noise, adding to background noise levels. Yet, speech intelligibility and speech privacy levels are expected to be superb to minimize errors due to miscommunication and to prevent the unintentional spread of confidential patient information. The acoustical challenge is to design operating rooms to control noise and to enhance room acoustics without affecting the performance of other systems. Speech intelligibility and impulse response measurements from modern hospital operating rooms and design strategies will be discussed.

In-vehicle speech intelligibility for different driving conditions using the Speech Transmission Index

The understanding of communications between passengers in an automobile as well as vehicle information systems to the driver is critical. A comprehensive study was conducted to evaluate speech intelligibility inside a vehicle for person to person communication using the Speech Transmission Index (STI). This metric provides a measure of the understanding or intelligibility of speech and has a value which varies from 0 for completely unintelligible to 1 for perfect intelligibility. For this study, several vehicle operating conditions, road surfaces and talker and listener configurations were compared in terms of the STI metric to gain a better understanding of these influences on in-vehicle person to person communication. Individual contributions of background noise and interior vehicle acoustics to the STI were also investigated. The results of this study found that higher in-vehicle sound pressure levels from engine and road noise are not necessarily associated with lower speech intelligibility. A wide range of STI values considered to be significant from subjective descriptions of intelligibility provided in the IEC EN 60268-16:2003 standard corresponding to those values were observed. These observations were for particular vehicle operating conditions, various configurations of the talker and the listener locations inside the vehicle, as well as between the ears of the listener at any particular location inside the vehicle. It was found that the rate of change of STI varied in unsteady background noise due to variable speed operation, at any given speed. It is recommended that subjective testing in a simulated vehicle environment be pursued to investigate any correlation of results with the STI metric. Also recommended is to determine the significance of the findings in terms of human perception of speech intelligibility inside a vehicle, and further investigate the appropriateness of using the STI metric, which is one of the most comprehensive speech intelligibility metrics available for a complete assessment of factors influencing in-vehicle person to person communication. Lastly, the effects of reverberation on reducing speech intelligibility were found to be negligible.

Sprachverständlichkeit und Krankheitsverarbeitung nach der Therapie von Mundhöhlenkarzinomen

Multimodal treatment of oral cancer can cause speech disorders and diminish speech intelligibility. Speech intelligibility is an essential part of social interaction and therefore important for coping with the disease. The aim of this study was to investigate the influence of speech intelligibility on coping strategies and a standardized questionnaire. Speech recordings from 76 patients 60.7 ± 11.4 years old (19 women, 57 men) were performed at least 6 months after multimodal treatment of T1-T4 squamous cell carcinoma of the oral cavity and evaluated by automatic speech recognition. Speech intelligibility was quantized as correctly recognized words of a standard text (word recognition rate WR). Coping was evaluated by the Trier Scales of Coping Strategies via questionnaires. Speech intelligibility scores WR rated between 22.2% and 84.3% (mean value 54.2 ± 15.7). Coping strategies vary considerably between the patients and between the scales. WR and the Trier Scales significantly correlate in 3 of the 5 categories (Rumination, Search for Information and Exchange of Experiences). Reduced speech intelligibility after multimodal treatment of oral cancer is associated with a change of coping strategy. This includes not only communication-based strategies (Search for Information and Exchange of Experiences) but also intra-psychic processes like rumination.

An evaluation of articulatory working space area in vowel production of adults with Down syndrome

Many adolescents and adults with Down syndrome have reduced speech intelligibility. Reasons for this reduction may relate to differences in anatomy and physiology, both of which are important for creating an intelligible speech signal. The purpose of this study was to document acoustic vowel space and articulatory working space for two adult speakers with Down syndrome who had reduced speech intelligibility (mean = 56% based on single words). Articulatory data for the tongue were collected using a real-time flesh-point tracking method (i.e. X-ray microbeam). Results show smaller F1–F2 acoustic vowel space area for both speakers with Down syndrome compared with the control speakers. Reduced articulatory working space area and slower movement speed were also found for three of the four tongue points analysed. Although generalizations are limited by the small number of participants, findings warrant further investigation of the underlying articulatory characteristics of speech production for individuals with Down syndrome.

Simulation of an EAS Implant with a Hybrid Vocoder

Although EAS electrode arrays are shorter, they have the same number of electrodes as conventional implant arrays. The possibility of channel interaction already exists with a standard length electrode array. As electrodes on an EAS array are closer together, the likelihood of channel interaction is even greater. To compensate for this, we proposed to deactivate several channels on the electrode array, on the premise that the reduction in speech intelligibility due to fewer channels would be offset by the low frequency residual hearing. Recent studies have demonstrated that low frequency residual hearing provides significant benefit for speech understanding (Dorman et al., 2005; Turner et al., 2004). This study aims to determine the number of channels necessary to provide good speech understanding according to the degree of low frequency residual hearing, particularly the boundary or cutoff frequency (Fc) between acoustic and electrical stimulation. This study utilized an acoustic simulation of an EAS device in normal-hearing subjects.

Intelligibility of speech produced under sleep-deprivation conditions.

In previous work, we applied the technique of acoustic landmark detection to speech produced under rested vs sleep-deprived conditions. We found significant differences for both the number and pattern of landmarks detected. In a parallel study we found significant differences in clear vs conversational styles of speech. While it has been shown by a number of investigators that clear and conversational speech styles differ in the degree to which intelligibility to listeners is preserved in noise, it is not clear whether the articulatory changes found in sleep-deprived speech affect the ability of listeners to understand what is said, especially in noise. In this paper, we present the results of a study in which normal-hearing listeners are asked to transcribe speech presented with and without background noise. Similar levels of background noise have been shown to reduce speech intelligibility for clear vs conversational speech presented to normal listeners. The speech in this study was produced under rested and sleep-deprived conditions. Results will be compared to effects of clear vs conversational speech presented in noise and in quiet.

Effects on speech intelligibility of temporal jittering and spectral smearing of the high-frequency components of speech

In a previous study, we demonstrated that word recognition performance was reduced when the low-frequency components of speech (0–1.2 kHz) were distorted by temporal jittering, but not when they were distorted by spectral smearing ( Pichora-Fuller et al., 2007). Temporal jittering distorts the fine structure of the speech signal with negligible alteration of either its long-term spectral or amplitude envelope characteristics. Spectral smearing simulates the effects of broadened auditory filters that occur with cochlear hearing loss ( Baer and Moore, 1993). In the present study, the high-frequency components of speech (1.2–7 kHz) were distorted with jittering and smearing. Word recognition in noise for both distortion conditions was poorer than in the intact condition. However, unlike our previous study, no significant difference was found in word recognition performance in the two distorted conditions. Whereas temporal distortion seems to have a deleterious effect that cannot be attributed to spectral distortion when only the lower frequencies are distorted, when the higher frequencies are distorted both temporal and spectral distortion reduce speech intelligibility.

Evaluation of the Increased Accident Risk From Workplace Noise

Directive 2003/10/EC sets the requirement for evaluating the effect of noise on accident risk. Accident risk is elevated for workers with a hearing handicap because of their reduced speech intelligibility and reduced capability to perceive the direction of incoming sound. An audiogram is not a good method for the evaluation of these functions. To reduce accident risk, organisational and personal solutions are needed. For both methods, efficiency must be evaluated through proper risk assessment. Because practical guidelines are not available, this paper presents principles for accident risk evaluation techniques.

Using HDC to evaluate signal similarity for information masking

In the many studies done on informational masking, interfering speech reduces speech intelligibility. This effect is often used to secure privacy in public spaces. These applications require estimates of how much masking is required. In general, masking effects are estimated by using spectrum information as excitation patterns. However, estimates of informational masking can hardly be obtained by only using spectrum information. Therefore, we estimated the effects of informational masking using time-domain information. Then, we calculated the cepstra of the envelopes’ magnitude histograms. If these cepstra are different between the target and the masker, the signals are not similar in the time-domain. Furthermore, the effect of informational masking would be low. Therefore, we considered the histograms’ cepstra distances (HCD) to estimate signal similarities. The signal similarities in our first experiment were estimated using five maskers by utilizing the HCD. These maskers were random noise, music, female speech, male speech, and target speaker’s speech. Male and female speech were more similar to the target speech than music and noise. Also, the same speaker’s speech was the most similar in the set of maskers. A listening test was carried out in the second experiment to verify the HCD. A double masker was used in this experiment as an effective informational masker. It has similar characteristics to reversal speech. The listening test results suggest the double-masker’s masking effects has the same relation with HCD. This suggests informational masking can be estimated by signal similarity using the HCD.

Medidas de inteligibilidade nos distúrbios da fala: revisão crítica da literatura

the reduction in speech intelligibility is considered one of the main characteristics of individuals with speech disorders, and is an important issue for clinical and research investigation. In spite of its relevance, the literature does not present a consensus on how to measure speech intelligibility. Besides the diversity of existent methods, another important issue refers to the influence of certain variables on these measurements and, consequently, on the interpretation of the results. to investigate evidence on the agreement between speech intelligibility measurements, obtained through different methods, used in the assessment of speech disorders, and to identify the effect of variables related to assessment procedures or to the listener. A critical review of articles indexed in the databases Medline, Web of Science, Lilacs and Scielo, until October 2007, was carried out. The key-word used to perform the search was speech intelligibility. there was no evidence of agreement between the speech intelligibility measurements obtained through different methods in the investigated literature. This fact limits the comparison between clinic and research results on speech intelligibility of individuals with speech disorders. Besides that, it was observed that some variables can interfere in these measurements, such as: type of task and speech stimulus, signal presentation mode, type of required answer and listener's experience with the speaker. These must be considered when interpreting the results of speech intelligibility tests.

The role of combined consonant duration and amplitude processing on speech intelligibility in noise

Reduced speech intelligibility in noise, especially consonant perception, is a well documented phenomenon. Research in clear speech has revealed many acoustic and phonetic differences between speech spoken in a conversational versus clear-speech mode. In the present study two components were tested in combination, namely increases in consonant duration (and respective decreases in adjacent vowel duration) and selective-consonant amplification. Conditions in which intelligibility improvements were observed for the individual processing of duration and amplitude modifications were chosen and tested in combination. The components were applied to Hearing-in-Noise Test sentences and consonant-vowel (CV) pairs. Stimuli were presented in sound field to normal-hearing individuals in the presence of speech-shaped noise. Percent correct was measured for HINT sentences and confusion matrices were developed for the CV pair intelligibility tests. An information transmission analysis was performed. Results will be discussed with regard to the greater body of research in clear speech.