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Replicating Dissociable Acoustic Signatures of Voice Improvement and Clinical Severity

Kodai Noguchi, M.S., Jennifer M. Roche, Ph.D., Hayley S. Arnold, Ph.D., CCC-SLP, Lynn V. Berk, M.A., CCC-SLP, Megan L. Malone, M.A., CCC-SLP, Jennifer Visker, M.A., CCC-SLP, Hannah Zetts, Erin Kolonich, M.A., CCC-SLP

Kent State University, Speech Pathology & Audiology, Kent, OH

Research Objectives

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Background

Method

Discussion

Results

References

Conclusion

Parkinson’s disease (PD) often leads to reduced vocal intensity and a decline in quality of life.

SPEAK OUT!® therapy focuses on “intentional” speech production to address these deficits.5, 7

Research shows SPEAK OUT!® increases vocal intensity in tasks like sustained vowels, reading, and conversation.2, 5, 8

Improvements are often sustained up to 6-12 months, especially with group maintenance sessions like the LOUD Crowd SPEAK OUT! Weekly Classes (formally known as LOUD Crowd).”1, 7, 8

Beyond intensity, the therapy improvesfundamental frequency (F0) range, intonation, and F0 variation1, 2, 3. Some studies show improvements in voice quality, measured by metrics like Cepstral Peak Prominence (CPP) and the Acoustic Voice Quality Index (AVQI), with some patients achieving levels comparable to those with no PD.2, 7

Clinician-rated measures like intelligibility, intonation, and dysarthria severity also show substantial positive changes.7

Patient subjective experience is crucial. Studies using the Voice Handicap Index (VHI) and Voice-Related Quality of Life (V-RQOL) scales show significant improvements after therapy.2, 3, 7

Prior research provides preliminary evidence that patient experience and clinical evaluation may depend on different acoustic cues. For instance, intensity and stability may influence patient-reported quality of life2, 3, 7, while F0 may affect clinician perceptions of severity.3

Although these findings provide a strong foundation, replication and further investigation is needed to enhance understanding about how subjective patient reports (VHI)4 and clinician-rated severity correlate with specific acoustic properties.2, 3, 7

This project aims to replicate these distinct acoustic signatures to better understand the mechanisms behind vocal improvement and treatment efficacy.

  1. To investigate how subjective self-reported measures (VHI) and clinician-rated measures (PDx) of voice map onto specific acoustic properties in individuals with PD.
  2. To evaluate pre- and post-treatment changes in core acoustic dimensions, specifically mean fundamental frequency (F0), F0 range, mean intensity, and intensity variability, following SPEAK OUT!® therapy.
  3. To examine whether changes in voice-related quality of life (VHI) and clinician perceived severity (PDx) predict systematic improvements in the overall acoustic profile and specific vocal outputs.
  4. To determine if patient experience and clinical evaluation rely on distinct acoustic cues (e.g., intensity and stability versus F0) to define treatment success.
  • Participants: Eleven individuals with PD (mean age = 66.5 years; 2 women, 9 men).
  • Intervention: SPEAK OUT!® therapy (8, 30-minute sessions delivered twice weekly over approximately four weeks (50% of the standard 12-session dosage), with acoustic variation and clinical measures evaluated pre- and post-treatment.
  • Procedure: Participants were evaluated using the Voice Handicap Index (VHI) and graduate student clinicians’ perceptions of severity (PDx) alongside standard SPEAK OUT!® elicitation procedures and scoring to predict acoustic variation.
  • Acoustic Analysis: Focused on four core interpretable dimensions of vocal production: 1) Mean F0, 2) F0 range, 3) Mean intensity, and 4) Intensity variability.
  • Statistical Model: Linear Mixed-Effects Model
  • Overall Acoustic Profile: There was a significant effect of VHI change on the overall acoustic profile, indicating that improvements in voice handicap (where higher values reflect greater improvement) were associated with systematic improvements in acoustic output (β = −0.54, SE = 0.17, t = −3.13, p = .002, R2c =.34).
    • Mean Intensity: Improvements in voice-related quality of life, measured via VHI change, were significantly associated with an increase in mean intensity (β = 0.55, SE = 0.16, t = 6.68, p < .001) (Fig. 1).
    • Intensity Variability: Improvements in voice-related quality of life were significantly associated with a decrease in intensity variability, reflecting greater vocal stability (β = −0.54, SE = 0.17, t = −3.13, p =.002) (Fig. 1).
    • F0 Range: Improvements in voice-related quality of life were significantly associated with a small but significant increase in the F0 range of the participants (β = 0.09, SE = 0.16, t = 3.81, p < .001) (Fig. 1).
    • Mean F0: Clinician perceived severity (PDx) was significantly associated with mean F0, indicating that clinicians tended to rate voices with higher F0 as being more severely affected (β = 0.71, SE = 0.15, t = 3.60, p < .001) (Fig. 2).
  • Voice Handicap Index (VHI) Scores: The mean difference in VHI scores from pre-treatment to post-treatment for the eleven participants was not statistically significant (mean difference = 9.68, p = .59).
  • Clinician Perceptions of Severity (PDx): The mean difference in clinician-rated severity from pre-treatment to post-treatment also did not reach statistical significance (mean difference = 2.50, p = .076).

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  • Changes in self-reported voice handicap (VHI) were systematically associated with multiple acoustic dimensions, including mean intensity, intensity variability, and F0 range, suggesting that patient-reported outcomes are sensitive to multidimensional acoustic changes.
  • In contrast, clinician-perceived severity (PDx) was primarily associated with mean F0, and not with other acoustic measures.
  • Despite measurable acoustic changes, neither VHI nor clinician severity ratings showed statistically significant pre and post differences, suggesting that acoustic measures may be more sensitive to subtle treatment-related changes than perceptual or rating-based measures.
  • These findings support the interpretation that patient experience and clinician judgment rely on partially distinct acoustic cues, with patient-reported outcomes reflecting broader acoustic changes and clinician ratings potentially relying on narrower cues such as F0.
  • Improvements in self-reported voice handicap were associated with systematic changes in intensity and F0 range, even in the absence of statistically significant pre andpost differences.
  • Clinician-perceived severity was primarily sensitive to mean F0, suggesting a narrower acoustic basis for perceptual judgments.
  • These findings indicate that acoustic measures may provide greater sensitivity to treatment-related change compared to clinician ratings.
  • A multidimensional framework integrating acoustic measures, self-report, and clinician evaluation is essential for accurately characterizing treatment outcomes.
  1. Behrman, A., Cody, J., Chitnis, S., & Elandary, S. (2022). Dysarthria treatment for

Parkinson’s disease: One-year follow-up of SPEAK OUT!® with the LOUD Crowd®. Logopedics Phoniatrics Vocology, 47(4), 271–278. https://doi.org/10.1080/14015439.2021.1958001

  • Behrman, A., Cody, J., Elandary, S., Flom, P., & Chitnis, S. (2020). The effect of SPEAK

OUT! and the LOUD Crowd on dysarthria due to Parkinson’s disease. American Journal of Speech-Language Pathology, 29(3), 1448–1465. https://doi.org/10.1044/2020_AJSLP-19-00024

  • Boutsen, F., Park, E., Dvorak, J., & Cid, C. (2018). Prosodic improvement in persons with

Parkinson disease receiving SPEAK OUT!® voice therapy. Folia Phoniatrica et Logopaedica, 70(2), 51–58. https://doi.org/10.1159/000488875

  • Jacobson, B. H., Johnson, A., Grywalski, C., Silbergleit, A., Jacobson, G., Benninger, M.

S., & Newman, C. W. (1997). The voice handicap index (VHI): Development and validation. American Journal of Speech-Language Pathology, 6(3), 66–70. https://doi.org/10.1044/1058-0360.0603.6

  • Levitt, J. S. (2014). A case study: The effects of the SPEAK OUT!® voice program for

Parkinson’s disease. International Journal of Applied Science and Technology, 4(2).

  • Levitt, J. S., & Walker-Batson, D. (2018). The effects of the “speak with intent” instruction

for individuals with Parkinson’s disease. Journal of Communication Disorders and Assistive Technology, 1, 1–15.

  • Levitt, J. S., Chitnis, S., & Walker-Batson, D. (2015). The effects of the SPEAK OUT!® and

LOUD Crowd® voice programs for Parkinson disease. International Journal of Health Sciences, 3(2), 13–19. https://doi.org/10.15640/ijhs.v3n2a3

  • Watts, C. R. (2016). A retrospective study of long-term treatment outcomes for reduced

vocal intensity in hypokinetic dysarthria. BMC Ear, Nose and Throat Disorders, 16, 2. https://doi.org/10.1186/s12901-016-0022-8

Figure 1. Mean centered acoustic cues (intensity, F0 range, and intensity variability) as a function of VHI change (higher = greater improvement).

Figure 2. Mean centered acoustic cue (mean F0) as a function of clinician perceived severity.