Measurement of Intelligibility in Disordered Speech

Simulating Speech Error Patterns Across Languages and Different Datasets

Children's speech acquisition is influenced by universal and language-specific forces. Some speech error patterns (or phonological processes) in children's speech are observed in many languages, but the same error pattern may have different effects in different languages. We aimed to explore phonological effects of the same speech error patterns across different languages, target audiences and discourse modes, using a novel method for large-scale corpus investigation. As an additional aim, we investigated the face validity of five different phonological effect measures by relating them to subjective ratings of assumed effects on intelligibility, as provided by practicing speech-language pathologists. Six frequently attested speech error patterns were simulated in authentic corpus data: backing, fronting, stopping, /r/-weakening, cluster reduction and weak syllable deletion-each simulation resulting in a "misarticulated" version of the original corpus. Phonological effects were quantified using five separate metrics of phonological complexity and distance from expected target forms. Using Swedish child-speech data as a reference, phonological effects were compared between this reference and a) child speech in Norwegian and English, and b) data representing different modes of discourse (spoken/written) and target audiences (adults/children) in Swedish. Of the speech error patterns, backing-the one atypical pattern of those included-was found to cause the most detrimental effects, across languages as well as across modes and speaker ages. However, none of the measures reflects intuitive rankings as provided by clinicians regarding effects on intelligibility, thus corroborating earlier reports that phonological competence is not translatable into levels of intelligibility.

Measuring intelligibility in spontaneous speech using syllables perceived as understood

PURPOSE

Intelligibility, the ability to convey a message by speech, is one of the most important variables in speech-language pathology. The assessment of intelligibility is a challenge especially when it comes to spontaneous speech. The aim of the study was to investigate validity and reliability of a method for assessment of intelligibility, syllables perceived as understood (SPU); a method that is more time-efficient than previous methods based on transcription, as it does not require a master transcript for reference.

METHOD

A group of 20 adult listeners transcribed stimuli consisting of spontaneous speech from 16 children (14 with speech sound disorder and two with typical speech and language development, age 4:4 to 8:1, M = 6:0). Intelligibility was calculated based on these orthographic transcripts, as a) proportion of syllables perceived as understood (SPU) and b) proportion of syllables correctly understood (SCU), with reference to a master transcript. Validity was checked through investigation of the correlation and difference between these two measures. Reliability was analysed with inter-listener reliability by intra-class correlation.

RESULTS

The correlation between SPU and SCU (the gold standard intelligibility score) was strong and statistically significant, with SPU being consistently higher than SCU. Inter-listener reliability for single measures of intra-class correlation of the assessment by syllables perceived as understood was moderate to low, whereas the inter-listener reliability for average measures of intra-class correlation was high.

CONCLUSIONS

The method based on SPU might be used for assessment of intelligibility if the median from several listeners is used or when comparing results from the same listener over time. The SPU method might therefore be a valuable tool in a clinical and research context as a more valid option than rating scales and a more time-efficient method than the gold standard SCU method. However, it should be noted that the reliability of the SPU is not as high as for the SCU.

Treatment of Phonological Disorder: A Feasibility Study With Focus on Outcome Measures

PURPOSE

In a feasibility study for a randomized controlled trial of treatments for phonological disorders conducted over a period of 8 months, we examined 6 clinically relevant outcome measures. We took steps to reduce error variance and to maximize systematic variance.

METHOD

Six children received traditional treatment (Van Riper, 1939), and 7 received expansion points (Smit, 2000), a treatment program with both phonological and traditional elements. Outcome measures, which were applied to both word list and conversational samples, included percentage of consonants correct (PCC; Shriberg & Kwiatkowski, 1982), PCC for late and/or difficult (L/D) consonants and number of L/D consonants acquired.

RESULTS

In repeated-measures analyses of variance, all measures showed significant differences from pretreatment to posttreatment, and the word list measures were associated with very high power values. In analyses of covariance for between-groups contrasts, the adjusted expansion points mean exceeded the adjusted traditional treatment mean for every measure; however, no differences reached significance. For the L/D PCC (conversation) measure, the contrast between groups was associated with a large effect size.

CONCLUSION

We recommend that practitioners use outcome measures related to a word list. We recommend that researchers consider using L/D PCC on the basis of conversational samples to detect differences among treatment groups.

SUPPLEMENTAL MATERIALS

https://doi.org/10.23641/asha.5872677.

Intelligibility as a clinical outcome measure following intervention with children with phonologically based speech-sound disorders

BACKGROUND

The effectiveness of two treatment approaches (phonological therapy and articulation therapy) for treatment of 14 children, aged 4;0-6;7 years, with phonologically based speech-sound disorder (SSD) has been previously analysed with severity outcome measures (percentage of consonants correct score, percentage occurrence of phonological processes and phonetic inventory). Considering that the ultimate goal of intervention for children with phonologically based SSD is to improve intelligibility, it is curious that intervention studies focusing on children's phonology do not routinely use intelligibility as an outcome measure. It is therefore important that the impact of interventions on speech intelligibility is explored.

AIMS

This paper investigates the effectiveness of the two treatment approaches (phonological therapy and articulation therapy) using intelligibility measures, both in single words and in continuous speech, as the primary outcome.

METHODS & PROCEDURES

Fourteen children with phonologically based SSD participated in the intervention. The children were randomly assigned to phonological therapy or articulation therapy (seven children in each group). Two assessment methods were used for measuring intelligibility: a word identification task (for single words) and a rating scale (for continuous speech). Twenty-one unfamiliar adults listened and judged the children's intelligibility. Reliability analyses showed overall high agreement between listeners across both methods.

OUTCOMES & RESULTS

Significant improvements were noted in intelligibility in both single words (paired t(6)=4.409, p=0.005) and continuous speech (asymptotic Z=2.371, p=0.018) for the group receiving phonology therapy pre- to post-treatment, but no differences in intelligibility were found for those receiving the articulation therapy pre- to post-treatment, either for single words (paired t(6)=1.763, p=0.128) or continuous speech (asymptotic Z=1.442, p=0.149).

CONCLUSIONS & IMPLICATIONS

Intelligibility measures were sensitive enough to show changes in the phonological therapy group but not in the articulation therapy group. These findings emphasize the importance of using intelligibility as an outcome measure to complement the results obtained with other severity measures when exploring the effectiveness of speech interventions. This study presents new evidence for the effectiveness of phonological therapy in improving intelligibility with children with SSD.

Assessment of intelligibility using children's spontaneous speech: methodological aspects

BACKGROUND

Intelligibility is a speaker's ability to convey a message to a listener. Including an assessment of intelligibility is essential in both research and clinical work relating to individuals with communication disorders due to speech impairment. Assessment of the intelligibility of spontaneous speech can be used as an overall indicator of the severity of a speech disorder. There is a lack of methods for measuring intelligibility on the basis of spontaneous speech.

AIMS

To investigate the validity and reliability of a method where listeners transcribe understandable words and an intelligibility score is calculated on the basis of the percentage of syllables perceived as understood.

METHODS & PROCEDURES

Spontaneous speech from ten children with speech-sound disorders (mean age = 6.0 years) and ten children with typical speech and language development (mean age = 5.9 years) was recorded and presented to 20 listeners. Results were compared between the two groups and correlation with percentage of consonants correct (PCC) was examined.

OUTCOMES & RESULTS

The intelligibility scores obtained correlated with PCC in single words and differed significantly between the two groups, indicating high validity. Inter-judge reliability, analysed using intra-class correlation (ICC), was excellent in terms of the average measure for several listeners.

CONCLUSIONS & IMPLICATIONS

The results suggest that this method can be recommended for assessing intelligibility, especially if the mean across several listeners is used. It could also be used in clinical settings when evaluating intelligibility over time, provided that the same listener makes the assessments.

A Phonetic Investigation of Single Word versus Connected Speech Production in Children with Persisting Speech Difficulties Relating to Cleft Palate

Objective

To investigate the phonetic and phonological parameters of speech production associated with cleft palate in single words and in sentence repetition in order to explore the impact of connected speech processes, prosody, and word juncture on word production across contexts.

Participants

Two boys (aged 9 years 5 months and 11 years 0 months) with persisting speech impairments related to a history of unilateral cleft lip and palate formed the main focus of the study; three typical adult male speakers provided control data.

Method

Audio, video, and electropalatographic recordings were made of the participants producing single words and repeating two sets of sentences. The data were transcribed and the electropalatographic recordings were analyzed to explore lingual-palatal contact patterns across the different speech conditions. Acoustic analysis was used to further inform the perceptual analysis and to make specific durational measurements.

Results

The two boys’ speech production differed across the speech conditions. Both boys showed typical and atypical phonetic features in their connected speech production. One boy, although often unintelligible, resembled the adult speakers more closely prosodically and in his specific connected speech behaviors at word boundaries. The second boy produced developmentally atypical phonetic adjustments at word boundaries that appeared to promote intelligibility at the expense of naturalness.

Conclusion

For older children with persisting speech impairments, it is particularly important to examine specific features of connected speech production, including word juncture and prosody. Sentence repetition data provide useful information to this end, but further investigations encompassing detailed perceptual and instrumental analysis of real conversational data are warranted.

Análise de variáveis utilizadas para a classificação da gravidade do desvio fonológico

OBJETIVO: analisar o comportamento das variáveis Percurso das Rotas, Nível de Complexidade e Aquisição de fonemas, conforme a classificação da gravidade do Desvio Fonológico (DF) por meio do Modelo Linguístico Fuzzy (BRANCALIONI, 2010). Além disso, verificar se a classificação da gravidade, por meio do Modelo, é capaz de diferenciar quantitativamente os graus quanto às classes de sons e aos traços distintivos. MÉTODO: a amostra foi constituída pela avaliação fonológica pré-tratamento de 204 sujeitos com DF, de ambos os sexos e idade entre quatro anos e dois meses a oito anos e dois meses. Todos os sujeitos foram submetidos à avaliação fonológica, avaliação da linguagem compreensiva e expressiva, avaliação do sistema estomatognático, exame articulatório repetitivo e avaliação audiológica. Foram realizadas as análises contrastiva e por traços distintivos. A gravidade dos 204 sistemas fonológicos desviantes foi classificada de acordo com o Modelo. Os valores correspondentes as variáveis foram tabulados e submetidos a tratamento estatístico por meio dos testes Tukey e Associação Qui-Quadrado complementado pela Análise de Resíduos Ajustados, considerando nível de significância de 5% (p<0,05). RESULTADOS: verificou-se que as variáveis Percurso das Rotas, Nível de Complexidade e Aquisição de Fonemas diminuem conforme se acentua a gravidade, sendo estas relações estatisticamente significantes. Além disso, observou-se que o número de classe de som alterada e de substituições de traços distintivos aumenta conforme se acentua a gravidade, sendo estas relações estatisticamente significantes. CONCLUSÃO: o Modelo é capaz de diferenciar os graus quanto às variáveis, trazendo informações importantes de acordo com os diferentes graus.

Validação de um modelo linguístico fuzzy para classificar a gravidade do desvio fonológico

OBJETIVO: verificar se os critérios adotados no Modelo Linguístico Fuzzy, para classificar a gravidade do Desvio Fonológico (DF), são empregados na prática fonoaudiológica e se estão de acordo com a finalidade do Modelo. Além disso, analisar a concordância entre a gravidade do DF classificada pelo Modelo e a julgada por fonoaudiólogas, bem como, verificar as principais dificuldades. MÉTODO: a pesquisa foi constituída por duas amostras. A primeira composta por um número representativo de sistemas fonológicos desviantes (n=52) classificados pelo Modelo quando o mesmo foi proposto. A segunda por dois grupos de fonoaudiólogas GF-I e GF-II. Foi solicitado que as fonoaudiólogas julgassem a gravidade dos sistemas fonológicos desviantes, mapeados no Modelo Implicacional de Complexidade de Traços - MICT, em Grave, Moderado-Grave, Moderado-Leve e Leve. Em seguida os critérios e as principais dificuldades foram descritas em um questionário. Empregou-se a Estatística Kappa, com nível de significância de p<0,05. RESULTADOS: os critérios utilizados na proposta, em geral, foram utilizados pelo GF-I e julgados adequados pelo GF-II. Verificou-se concordância entre a classificação da gravidade obtida pelo Modelo com a julgada pelas fonoaudiólogas. Quanto às dificuldades, a frequentemente relatada foi diferenciar graus intermediários. CONCLUSÕES: os critérios utilizados no Modelo Linguístico Fuzzy são empregados para classificar a gravidade do DF quando realizada com base no MICT. Além disso, os critérios empregados estão de acordo, cumprindo com a finalidade do Modelo. Diante das dificuldades, outras formas de classificar a gravidade podem ser agregadas a fim de caracterizar o DF sobre outros aspectos importantes.

Developing a weighted measure of speech sound accuracy

PURPOSE

To develop a system for numerically quantifying a speaker's phonetic accuracy through transcription-based measures. With a focus on normal and disordered speech in children, the authors describe a system for differentially weighting speech sound errors on the basis of various levels of phonetic accuracy using a Weighted Speech Sound Accuracy (WSSA) score. The authors then evaluate the reliability and validity of this measure.

METHOD

Phonetic transcriptions were analyzed from several samples of child speech, including preschoolers and young adolescents with and without speech sound disorders and typically developing toddlers. The new measure of phonetic accuracy was validated against existing measures, was used to discriminate typical and disordered speech production, and was evaluated to examine sensitivity to changes in phonetic accuracy over time. Reliability between transcribers and consistency of scores among different word sets and testing points are compared.

RESULTS

Initial psychometric data indicate that WSSA scores correlate with other measures of phonetic accuracy as well as listeners' judgments of the severity of a child's speech disorder. The measure separates children with and without speech sound disorders and captures growth in phonetic accuracy in toddlers' speech over time. The measure correlates highly across transcribers, word lists, and testing points.

CONCLUSION

Results provide preliminary support for the WSSA as a valid and reliable measure of phonetic accuracy in children's speech.

O uso das estratégias de reparo, considerando a gravidade do desvio fonológico evolutivo

OBJETIVO: analisar a relação entre as estratégias de reparo utilizadas pelo grupo com desvio fonológico evolutivo (DFE) e a gravidade do desvio apresentado. MÉTODOS: amostra de fala de 12 sujeitos (6 meninos e 6 meninas), idades entre 4:00 a 6:11;29, com diagnóstico de desvio fonológico evolutivo. Os dados foram analisados estatisticamente através do Pacote Computacional VARBRUL em ambiente Windows (Varbwin). RESULTADOS: a gravidade de Desvio Severo (DS) tem maior probabilidade de realizar plosivização, posteriorização, e outras, assim como semivocalização. A Gravidade de Desvio Moderado-Severo (DMS) favorece a ocorrência de anteriorização, dessonorização e outras. A Gravidade do Desvio Médio-Moderado favorece a posteriorização, a semivocalização e a dessonorização. A Gravidade de Desvio Médio apresentou maior probabilidade de realização de posteriorizações e anteriorizações. CONCLUSÃO: quanto maior a gravidade do desvio fonológico, mais as crianças utilizam estratégias de reparo, pois ainda não conhecem o segmento ou trata-se de produção que ainda não dominam.

A inteligibilidade do desvio fonológico julgada por três grupos de julgadores

TEMA: a inteligibilidade do desvio fonológico. Objetivo: comparar a inteligibilidade julgada do desvio fonológico a partir da análise de três grupos distintos de julgadores. MÉTODO: a pesquisa foi composta de duas amostras, uma amostra julgada (30 sujeitos com desvio fonológico) e outra julgadora (fonoaudiólogas, leigas e mães). Foi analisada a fala espontânea das crianças através da narração de três seqüências lógicas, as quais foram analisadas pelas julgadoras, acompanhadas por algumas questões para marcação da inteligibilidade. Para análise dos dados, foi realizada a MODA das 90 narrativas, possibilitando a análise estatística dos dados através da análise de concordância-Kappa. RESULTADOS: a análise mostrou maior concordância entre os grupos de juízes para os extremos das possibilidades de julgamento (boa e insuficiente). A concordância entre todos os grupos de julgadores foi substancial para o julgamento da inteligibilidade boa sendo mais difícil o julgamento da inteligibilidade regular. CONCLUSÃO: observou-se que quanto mais foi julgada ininteligível a fala, mais severa foi a sua classificação pelos grupos de julgadores participantes.

Cross-Dialectal Perceptual Experiences of Speech-Language Pathologists in Predominantly Caucasian American School Districts

Purpose

This study aimed to determine if the number and type of African American English (AAE) features that are spoken in sentences influence speech-language pathologists' (SLPs') judgments of (a) how noticeable the dialect is (dialect detectability) and (b) how understandable a speaker is to others (comprehensibility).

Method

Certified SLPs with little conversational experience with AAE were recruited from predominantly Caucasian American school districts in Michigan. They listened to sentences that contained varying amounts and types of AAE phonological features. The SLPs rated the sentences on 5-point scales regarding dialect detectability and comprehensibility. The ratings for the different sentences were compared to determine how the variables contributed to the SLPs' judgments of AAE.

Results

Both dialect detectability and comprehensibility ratings were affected by the number of AAE features that were included in the sentences. The types of AAE features consistently affected the comprehensibility ratings but less consistently affected the dialect detectability ratings.

Conclusion

Multiple factors may affect SLPs' perceptions of AAE. The outcomes have both theoretical and practical implications.

Teachers' Perceptions of Students With Speech Sound Disorders: A Quantitative and Qualitative Analysis

Purpose

This study examined 2nd-grade teachers' perceptions of the academic, social, and behavioral competence of students with speech sound disorders (SSDs).

Method

Forty-eight 2nd-grade teachers listened to 2 groups of sentences differing by intelligibility and pitch but spoken by a single 2nd grader. For each sentence group, teachers rated the speaker’s academic, social, and behavioral competence using an adapted version of the Teacher Rating Scale of the Self-Perception Profile for Children (S. Harter, 1985) and completed 3 open-ended questions. The matched-guise design controlled for confounding speaker and stimuli variables that were inherent in prior studies.

Results

Statistically significant differences in teachers' expectations of children’s academic, social, and behavioral performances were found between moderately intelligible and normal intelligibility speech. Teachers associated moderately intelligible low-pitched speech with more behavior problems than moderately intelligible high-pitched speech or either pitch with normal intelligibility. One third of the teachers reported that they could not accurately predict a child’s school performance based on the child’s speech skills, one third of the teachers causally related school difficulty to SSD, and one third of the teachers made no comment.

Conclusion

Intelligibility and speaker pitch appear to be speech variables that influence teachers' perceptions of children’s school performance.