Systematic Review of Literature on Vocal Demand Response: Understanding Physiology, Measurements, and Associated Factors

PURPOSE

Considering the conceptual migration from vocal load and vocal loading to vocal demand and vocal demand response, this review of literature aimed to identify physiological explanations, reported measurements, and associated factors (vocal demands) reported in the literature when considering the phonatory response to a vocal demand.

METHODS

A systematic review of literature, following the PRISMA Statement, was conducted using Web of Science, PubMed, Scopus, and ScienceDirect. Data were analyzed and presented in two parts. First, a bibliometric analysis, co-occurrence analysis, and content analysis were performed. Three criteria that got article inclusion were defined: (1) written in English, Spanish, and Portuguese; (2) published between 2009 and 2021; and (3) focused on vocal load and loading, vocal demand response, and voice assessment parameters. A total of 54 publications met the criteria and were included in this review. The second part included a conceptual framework based on the content analysis of three aspects of vocal demand response: (1) physiological explanations, (2) reported measurements, and (3) vocal demands.

RESULTS AND CONCLUSION

As would be expected since vocal demand response is a relatively new term and not yet commonly used in literature when discussing way that the speakers respond to communicative scenarios, most of the studies reviewed (both historical and recent) still use the term of vocal load and vocal loading. Although there is a broad variety of literature discussing a wide range of vocal demands and voice parameters used to characterize the vocal demand response, results show that there is consistency across the studies. While vocal demand response is unique and intrinsic to the talker, associated factors that contribute to this response include both internal talker and external talker factors. Internal factors include muscle stiffness, viscosity in the phonatory system, vocal fold tissue damage, elevated sound pressure levels during occupational voice demands, extended periods of voice use, suboptimal body posture, difficulties in breathing technique, and sleep disturbances. Associated external factors include the working environment (noise, acoustics, temperature, humidity). In conclusion, although vocal demand response is intrinsic to the speaker, the speaker's response is affected by external vocal demands. However, due to the wide methods to evaluate vocal demand response, it has been difficult to establish its contribution to voice disorders in the general population and, specifically, among occupational voice users. This literature review identified commonly reported parameters and factors that may help clinicians and researchers define vocal demand response.

Relations between Creaky Voice and Vocal Symptoms of Fatigue

BACKGROUND

The use of a creaky voice in speech has become more common. Laryngeal findings relate creaky voice with strong adductive tension in the glottis, and thus it may be expected to be related to an increased risk of vocal fatigue.

METHODS

The present study investigated the relation of creaky voice use and vocal symptoms in 104 Finnish female university students (mean age 24.3 years, SD 6.3 years). They had no known pathology of voice or hearing. The participants were recorded while reading aloud a text of approximately 40 s in duration. They also filled in a questionnaire consisting of the Voice Handicap Index (VHI, translation in Finnish), and half of them also answered questions about the frequency and severity of symptoms of vocal fatigue. The samples were perceptually analysed for the amount of creakiness and strain by a speech therapist and a voice trainer.

RESULTS

The interrater reliability of the listeners was acceptable (Pearson's χ2 = 100.159, p = 0.000 for creak; χ2 = 69.199, p = 0.000 for strain). Neither creakiness nor strain correlated with vocal symptoms. Participants with a low and a high amount of creakiness or strain did not differ from each other in terms of vocal symptoms or VHI scores. Symptoms' total score correlated with VHI total score and total scores of VHI's physical subscale. Creakiness and strain correlated positively with each other (r = 0.40, p = 0.000).

CONCLUSION

No significant relations were found between creakiness or strain and vocal symptoms in this sample of university students.

Eficiência e valores de corte do Perfil de Participação e Atividades Vocais para não professores e professores

RESUMO Objetivos: Identificar características de eficiência e valores de corte das dimensões do protocolo Perfil de Participação e Atividades Vocais - PPAV que discriminam disfônicos de indivíduos vocalmente saudáveis; verificar se a nota de corte permanece a mesma para uma amostra de professores. Métodos: Características de eficiência e valores de corte dos dados do PPAV de 171 indivíduos foram analisados por meio da curva ROC (Receiver Operating Characteristic curve ): 90 professores (60 disfônicos e 30 vocalmente saudáveis, com médias de idade semelhantes, p=0,418) e 81 indivíduos não professores (48 disfônicos e 33 vocalmente saudáveis, com média de idade semelhantes, p=0,934). Resultados: Os valores de área sob a curva ROC - AUC e os valores de corte do escore total do PAVV que separam indivíduos com e sem disfonia são diferentes para não professores e professores. Indivíduos não professores apresentaram AUC = 0,986 (p<0,001) e 4,5 pontos no escore total do PPAV (sensibilidade=95,8% e especificidade=90,9%); já os professores apresentaram AUC = 0,872 (p<0,001) e nota de corte de 14,6 pontos (sensibilidade=91,7% e especificidade=75,9%). Conclusão: A nota de corte do PPAV é diferente para não professores e professores, sendo maior para os professores, porém, com maior sensibilidade e especificidade para os indivíduos não professores, podendo ser utilizado para triagens de grandes populações de risco para alteração de voz.

Vocal Loading in Speaking a Foreign Language

AIMS

This study investigated whether speaking a foreign language affects the subjective notions of vocal fatigue, and whether acoustic measurements reveal a higher vocal loading.

METHODS

The speech samples of 20 native Finnish-speaking and 23 native English-speaking subjects were recorded in Finnish and in English. From the speech samples, fundamental frequency, equivalent sound level, total duration of voiced speech, speech rate, alpha ratio and L1-L0 level difference were analyzed. Vocal doses were calculated.

RESULTS

According to subjective notions, the voice gets tired more quickly when speaking a foreign language. The mean fundamental frequency increased but the speech rate and total duration of voiced speech decreased significantly when speaking a foreign language. Thus, the vocal doses decreased.

CONCLUSIONS

The subjective sensations of increased vocal fatigue may be due to increased mental stress rather than to higher vocal loading. However, a trend that speaking a foreign language may involve more loading was found in L1-L0 level difference and in the doses normalized to time dose. Longer speech samples should be studied. Voice quality-based indicators of vocal loading are worth testing in addition to the measures based on the amount of voicing in speech.