Pitch and resonance are two features of the voice, but they are not measured in exactly the same way. The American Speech-Language-Hearing Association (ASHA) describes both listening judgments and acoustic measurements as parts of a voice evaluation. This article explains those terms and what ASHA says a speech-language pathologist (SLP) may assess.
This is general professional information, not a diagnosis. ASHA says physicians are the only professionals qualified and licensed to make medical diagnoses related to laryngeal pathology. It says consultation with an otolaryngologist can be important, and that only otolaryngologists can diagnose organic pathologies. An SLP evaluates voice function and communication.
Pitch and resonance describe different things
In everyday language, pitch is how high or low a voice sounds. ASHA's assessment material uses fundamental frequency, abbreviated F0 and measured in hertz (Hz), as the acoustic measure connected with vocal frequency.
Resonance is not the same as pitch. In the voice-disorders assessment, ASHA describes a clinician judging resonance quality and where the voice seems focused. The categories include typical or normal, hyponasal, hypernasal and cul-de-sac resonance. When resonance is judged normal, the described focus may be oral, pharyngeal or laryngeal, or nasal.
A voice can therefore be described by its pitch and, separately, by a resonance judgment. The two results answer different assessment questions.
What happens in the evaluation
ASHA's voice-disorders practice guidance describes a broad evaluation rather than a single pitch test. It includes:
- a case history
- the person's own rating of how the voice affects daily life
- an oral-peripheral examination, including laryngeal sensation
- breathing pattern and the timing between breath and voice
- listening to vowels, sentences and running speech
A screening may cover respiration, phonation, resonance, pitch, loudness, pitch range and endurance. Informal tasks or formal screening tools may be used, and a questionnaire may be part of screening.
ASHA says diagnostic therapy can test whether a person is stimulable to voice therapy. It also says abnormal resonance is assessed for stimulability, meaning whether it changes with cues. Those observations describe how the voice responds during assessment. They are not a medical diagnosis, and a change during the session does not by itself establish a lasting result.
How pitch is rated and measured
ASHA describes two complementary approaches.
The listening approach uses a perceptual framework called the Consensus Auditory-Perceptual Evaluation of Voice, or CAPE-V. The rated features include roughness, breathiness, strain, pitch, loudness and overall severity. Additional descriptions can include diplophonia, aphonia, pitch instability, tremor, vocal fry, falsetto, and a wet or gurgly quality. These are clinician impressions made while listening to sustained vowels, sentences and running speech.
The acoustic approach names these frequency measures:
- mean vocal F0, in Hz
- minimum and maximum vocal F0, in Hz
- the standard deviation of vocal F0, in Hz
ASHA also lists loudness-related measures: habitual sound pressure level (SPL), and minimum and maximum SPL, in decibels (dB). For signal quality, it names cepstral peak prominence, or CPP, in dB, measured on sustained vowels and connected speech.
ASHA also lists aerodynamic measures separately from pitch: average glottal airflow rate and average subglottal air pressure. Its respiration assessment includes maximum phonation time and the s/z ratio, which it uses to assess glottal insufficiency. These are additional parts of the evaluation, not pitch measurements.
How resonance is judged
ASHA's described resonance assessment is primarily a listening judgment. The clinician judges whether resonance is normal, hyponasal, hypernasal or cul-de-sac, and may describe the focus of a voice judged normal as oral, pharyngeal or laryngeal, or nasal.
The practice material also says abnormal resonance is assessed for stimulability, meaning whether it changes with cues. A response during that check describes the assessment. It does not establish that a change will last.
ASHA's voice-evaluation material cited here does not reduce resonance to one number in the way it reports F0 in hertz. A report may therefore describe pitch with measurements and describe resonance with perceptual categories.
Why the numbers need context
ASHA gives an important limit: the severity of a voice disorder cannot always be determined from auditory-perceptual voice quality alone. A listener's impression is useful, but it does not establish the cause or the full severity of a problem.
ASHA places those recording limits in its discussion of aerodynamic assessment, not in the pitch section. It says sources of error may contribute to inaccurate data, and it names instrument quality and calibration, microphone distance, the acoustic qualities of the room, and ambient noise.
For that reason, a careful report should identify the task, such as a sustained vowel or connected speech, and interpret the result in the context of the examination. ASHA says physicians are the only professionals qualified and licensed to make medical diagnoses related to laryngeal pathology, and that only otolaryngologists can diagnose organic pathologies. Imaging used for that purpose is interpreted by a trained otolaryngologist.
Questions to ask the clinician
- Which listening ratings and acoustic measures will be used?
- Will mean, minimum and maximum F0 all be measured, and on which tasks?
- How will resonance be described if it is not reported as one number?
- How were the recordings made, and what limitations could affect them?
- Has a physician examined my larynx, or does the SLP recommend that examination?
- Which results relate to my personal voice goal, and which are only baseline observations?
Key takeaways
- ASHA describes pitch through both listening ratings and F0 measurements in hertz.
- Resonance is judged with categories such as normal, hyponasal, hypernasal and cul-de-sac, not simply as a pitch value.
- A voice evaluation can also include history, breathing, loudness, CPP, aerodynamic measures and the person's own rating of daily impact.
- Perceptual quality alone does not establish severity or cause, and recording conditions can affect acoustic results.
- Medical diagnosis of a laryngeal condition belongs to a physician. ASHA says only an otolaryngologist can diagnose an organic pathology.