HNR in Voice Assessment: A Guide for SLPs Using Phonalyze

Overview: Why HNR Matters in Clinical Voice Assessment

Harmonic-to-Noise Ratio is a foundational acoustic metric that quantifies the balance between periodic (harmonic) energy and aperiodic (noise) energy in a voice signal. In clinical terms, HNR offers an objective window into patient-perceived breathiness and roughness—dimensions that commonly co-occur with dysphonia, vocal fold pathology, and inefficient phonation.

High HNR indicates a predominantly periodic, “cleaner” signal consistent with clearer vocal quality.
Low HNR indicates greater noise contribution, often associated with breathiness, roughness, or irregular vocal fold vibration.

For speech-language pathologists (SLPs), Harmonic-to-Noise Ratio complements perceptual measures (e.g., CAPE-V, VHI-10) by providing a robust, reproducible acoustic index that tracks change over time. HNR and associated metrics are operationalized by Phonalyze in a cloud-based, HIPAA-compliant process designed for clinical evaluation and long-term tracking in both in-person and remote practice environments.

Phonalyze at a Glance (SLP-Centered)

Phonalyze is a cloud-based SaaS platform for SLPs that unifies objective acoustic analysis and subjective perceptual surveys within a single, secure workflow. It leverages PRAAT—the widely used speech analysis engine—to compute validated metrics including HNR, jitter, shimmer, F0, CPP/CPPS, AVQI, and more. Highlights for clinical practice:

Web-based: No app installs for clinicians or patients
HIPAA-compliant: Patient confidentiality by design
High-fidelity capture: Accurate input for reliable analysis
Rapid reports: Acoustic measures delivered in minutes
PRAAT integration: Transparent, validated signal processing
Remote-ready: Secure SMS task delivery protects clinician privacy
Flexible subscriptions: Month-to-month (~$1/day), free 30-day trial
Individual and Group: Collaborative access with longitudinal tracking

What Is Harmonic-to-Noise Ratio (HNR)?

HNR expresses, typically in decibels (dB), the relative amount of periodic energy (harmonics produced by regular vocal fold vibration) compared to aperiodic energy (noise arising from turbulent airflow, irregular vibration, or measurement conditions). Conceptually:

Periodic energy corresponds to the harmonic series at integer multiples of fundamental frequency (F0).
Aperiodic energy is broadband and non-harmonic, elevating the noise floor of the acoustic spectrum.

Mathematically, Harmonic-to-Noise Ratio is often defined as 10·log10(Harmonic Power / Noise Power). Because it is a ratio in dB, higher values denote a greater dominance of harmonic energy. Clinically, that correlates with clearer, more periodic phonation.

How HNR Is Computed in PRAAT (as used in Phonalyze)

Phonalyze integrates PRAAT to ensure transparent, reproducible, and clinically recognized computation. While PRAAT provides multiple harmonicity methods, a common approach includes:

Time-domain or cepstral-based estimation of periodicity.
Separation of harmonic and noise components through pitch-synchronous analysis (leveraging F0 and its harmonics).
Calculation of a harmonicity measure over analysis frames, then summarized (mean/median) across the task segment.

Key computation considerations:

Window size and step size: Balance temporal resolution with estimation stability.
Voiced/unvoiced decisions: HNR is computed where voicing is detected.
Intensity thresholds and pitch floor/ceiling: Accurate F0 tracking supports reliable harmonic/noise decomposition.

Phonalyze standardizes these parameters per task type to provide consistent, clinically interpretable outputs while maintaining the traceability of PRAAT-derived measures in the report.

Interpreting Harmonic-to-Noise Ratio in Clinical Context

HNR should be interpreted relative to task type, patient demographics, and other acoustic/perceptual indicators. General interpretive guidance:

Higher HNR (e.g., mid-to-high teens or above) typically reflects more periodic, less noisy phonation commonly perceived as clearer or less breathy.
Lower HNR suggests increased aperiodicity/noise—often aligning with breathiness, roughness, glottal insufficiency, or irregular vibratory patterns.

Harmonic-to-Noise Ratio vs. Related Measures: How They Work Together

Jitter (cycle-to-cycle frequency perturbation): Elevated jitter indicates irregular F0 period timing. Low HNR and high jitter often co-occur in rough/breathy voices but represent different phenomena.
Shimmer (cycle-to-cycle amplitude perturbation): Elevated shimmer signals amplitude instability. Combined with low HNR, it can strengthen evidence of aperiodicity and glottal inefficiency.
Fundamental Frequency (F0): Accurate pitch tracking underpins reliable harmonic estimation. Extreme F0 ranges or voice breaks can affect HNR stability.
Cepstral Peak Prominence (CPP/CPPS): Sensitive to periodic energy in connected speech; CPP/CPPS and HNR often trend together. CPP/CPPS can be robust to certain noise conditions and is central in dysphonia assessment.
AVQI: A composite index combining multiple acoustic features (often including CPP-related and spectral measures) to assess dysphonia severity in running speech.

Clinical Use Cases

Baseline characterization
- Establish a patient’s periodicity profile prior to therapy or surgery.
- Pair with perceptual scales (CAPE-V, VHI-10, V-RQOL) for multidimensional insight.
Differential insight into breathiness and roughness
- Low HNR supports perceptual impressions of breathiness due to increased turbulence or glottal leak.
- Low HNR with elevated jitter/shimmer may indicate irregular vibratory behavior contributing to roughness.
Treatment monitoring
- Track HNR longitudinally to evaluate therapy efficacy for conditions such as vocal fold paresis, nodules, or post-surgical recovery.
  Use task-specific comparisons (e.g., sustained /a:/ vs. CAPE-V sentences) to assess generalizability of improvements.
Light to moderate dysphonia screening in remote care
- Phonalyze high-quality capture plus PRAAT integration enables reliable HNR estimation in telepractice, with immediate reports for timely decisions.
Research and protocol development
- Combine HNR with CPP/CPPS and AVQI to examine multidimensional dysphonia signatures.

Export CSVs for statistical modeling, correlating acoustic features with perceptual scores and patient-reported outcomes.

Task Selection in Phonalyze for Reliable HNR

Phonalyze includes a curated set of tasks to capture Harmonic-to-Noise Ratio across controlled and ecological contexts:

Sustained Vowels (“aaah”, “eeee”): Ideal for stable HNR estimates and clean comparisons session-to-session.
Conversational Speech (10s, 15s) and CAPE-V Sentences: Capture HNR under natural articulation; interpret in tandem with CPP/CPPS and AVQI.
Quiet and Strong Productions: Observe how intensity changes affect periodicity; stronger phonation may increase HNR if glottal closure improves.
Pitch Glides: Useful for observing how HNR varies across F0 range; watch for breaks or instability.
Grandfather/Rainbow Passages: Longer connected speech samples where HNR variability can reflect real-world function.

How Phonalyze Computes and Reports HNR

Acquisition
- Patient completes tasks in-person or via secure SMS link from a Phonalyze number.
- High-quality audio captured on the patient’s phone or clinician’s device.
Processing
- High quality audio securely transmitted to Phonalyze’s HIPAA-compliant cloud.
- PRAAT engines compute HNR alongside jitter, shimmer, F0, CPP/CPPS, AVQI, intensity, and more.
Reporting
- HNR presented per task with summary statistics (e.g., mean/median) and validity flags where applicable.
- Clinicians receive immediate email notification plus online access within minutes.

Normative Thinking and Cautions

Harmonic-to-Noise Ratio distributions vary with age, sex, task type, intensity, and device specifics. Rather than applying rigid cutoffs, Phonalyze emphasizes:

Within-subject comparison: Track change relative to each patient’s baseline.
Task-consistent comparisons: Compare like with like (e.g., sustained /a:/ at similar loudness).
Multi-metric convergence: Seek alignment across HNR, CPP/CPPS, jitter, shimmer, AVQI, and perceptual surveys.

This approach respects clinic variability while preserving clinical significance.

Incorporating Perceptual Surveys

Use Phonalyze to pair HNR with standardized voice tasks and perceptual questionnaires:

VHI-10, V-RQOL: Capture perceived impact on daily function.
RSI, EAT-10, DI, NLHQ: Contextualize voice within reflux, swallowing, dyspnea, and hypersensitivity profiles.
Gender-affirming tools (e.g., TSEQ, Trans Women Voice Questionnaire, Nonbinary Voice Experiences): Integrate HNR tracking with targeted goals like clarity, resonance, or fatigue.

Why SLPs Choose Phonalyze for HNR and Beyond

Built for SLPs: Clinical tasks, perceptual surveys, and reports tuned for therapy workflows.
PRAAT under the hood: Validated, transparent computation of HNR and related metrics.
HIPAA-first: Security without sacrificing speed or usability.
Remote-native: Encrypted SMS task delivery. No app installs. Faster patient compliance.
Cost-effective: Month-to-month pricing around $39/month with a 30-day free trial.
Collaborative and scalable: Individual or group plans, longitudinal tracking, CSV exports.
Continuously improving: Feature roadmap guided by SLP feedback and advisor input.

Call to action: Start free trial at phonalyze.com.

More Blogs for Clinical Depth

Shimmer in voice assessment: https://blog.phonalyze.com/understanding-shimmer-in-voice-assessment-with-phonalyze/
Fundamental frequency (F0): https://blog.phonalyze.com/understanding-f0-fundamental-frequency-in-voice-assessment-with-phonalyze/
CPP vs. CPPS: https://blog.phonalyze.com/cpp-vs-cpps-which-voice-measure-should-you-use/
Interpreting PRAAT results: https://blog.phonalyze.com/interpreting-praat-results/

Conclusion

Phonalyze brings PRAAT-grade HNR analysis into a fast, HIPAA-compliant, and remote-ready workflow designed for SLPs and other voice professionals. Measure, monitor, and communicate voice outcomes with objective clarity.

Start free trial at phonalyze.com.

FAQ

What does a higher or lower HNR mean clinically?

Higher HNR: More periodic, “cleaner” signal—often perceived as clearer voice quality.
Lower HNR: Greater aperiodic/noise energy—often associated with breathiness or roughness. Always interpret with other measures and perceptual ratings.

Which tasks are best for measuring HNR?

Sustained vowels (“aaah”, “eeee”) provide stable baselines. Include connected speech (CAPE-V sentences, conversational speech) to evaluate generalization in natural contexts.

How does HNR relate to jitter and shimmer?

HNR captures periodic vs. noise energy balance; jitter and shimmer capture cycle-to-cycle perturbations in frequency and amplitude. They often trend together in dysphonia but represent distinct phenomena. Use all three for a fuller picture.

Can environment or device affect HNR?

Yes. Background noise and inconsistent mic distance can lower HNR artificially. Phonalyze’s capture guidance and high-fidelity protocols help minimize these effects. Re-record questionable takes.

How quickly are HNR results available?

Within minutes of task completion. Phonalyze emails results and updates the online report immediately, supporting same-session interpretation and planning.

Is HNR enough to diagnose dysphonia?

No single acoustic measure should be used for diagnosis. Combine HNR with CPP/CPPS, jitter, shimmer, AVQI, perceptual measures (CAPE-V, VHI-10), case history, and clinical examination.