3.3.1 What is voice?

Your voice is unique to you and is connected with your identity.  Our voice expresses a lot of the meaning we want to say to others.  We can convey our personality, emotions and general health via our voice and it’s quality. Everyone has a unique voice and difference voice quality.  The quality of our voice is influenced by factors such as the shape and size of the vocal cords, the size of the resonatory space in the vocal tract, and the way the vocal cords vibrate.  But how is voice produced?  Essentially, voice is produced via the coordinated movement of body structures such as the respiratory system (e.g. lungs, diaphragm) and the phonatory system in the larynx (e.g. vocal cords).

The video below provides an overview of how we produce voice (or vocalisations) and speech.

^{How does the human body produce voice and speech? by National Institutes of Health}

3.3.2 Voice disorders

A voice disorder (or dysphonia) can be described as where an individual’s voice (i.e. pitch, loudness, resonance, or phonatory quality) differs significantly from that of persons of a similar age, gender, or cultural background (Colton et al., 2011).

Below are common terminologies used to describe different aspects voice quality or irregularities in voice production. Analysis of these features, and considering the person’s case history, can often assist us with forming hypotheses regarding specific conditions or vocal habits that may be contributing to the voice disorder:

Voice quality terminologies

Pitch refers to how high (upper end of a scale) or low (bottom end of a scale) a sound is perceived by a listener. Pitch is determined by the frequency (measured in hertz – Hz) of the vibrations produced by the vocal cords. When the vocal cords vibrate faster, they produce a higher pitch (like a soprano voice), and when they vibrate slower, the pitch is lower (like a bass voice). Pitch is the acoustic correlate that allows us to distinguish between a high note and a low note when singing or speaking.

Pitch breaks may when the voice unexpectedly changes pitch, usually during speaking or singing. Typically this happens when the vocal cords suddenly loosen or tighten, leading to an involuntary change in pitch.  Examples of when pitch breaks may occur is during puberty or when people have vocal strain (i.e. excessive tightness in the vocal folds preventing smooth and even movement).

Loudness refers to the volume of the voice, or how soft or loud the sound is. Loudness is measured in decibels (dB). Loudness is influenced by the amount of air pushed through the vocal cords and how much tension is applied to them. Louder sounds come from greater airflow and increased tension in the vocal folds, whereas softer sounds come from less air and more relaxed vocal folds.

Resonance refers to the way the sound is amplified and modified by the vocal tract, including the throat, mouth, and nasal passages. These structures act like a resonating chamber, shaping and enriching the sound produced by the vocal cords. Resonance adds richness and depth to the voice.  Some people may experience, for example, hypernasality or hyponasality when speaking.  Hypernasality is when too much air escapes through the nasal passage during speech.  Hyponasality occurs when there is insufficient airflow through the nose, making the voice sound stuffy or blocked. Changes in resonance also helps determine which speech sound a person is saying (such as ‘ah’ compared to ‘oo’)

Quality of voice encompasses several aspects. The following terms relating to the quality of a voice are often used interchangeably when people describe a dysphonic voice. Speech Pathologists typically use a more formal set of terms and definitions to describe voice quality. Here are some examples of these terms:

• Breathiness (or breathy voice quality) means there’s excess air escaping through the vocal folds when a person is speaking or singing. This can happen if the vocal cords don’t close fully during voice production (phonation), allowing air to escape between the vocal folds even though the vocal folds are still vibrating enough to create some voice.  A breathy voice often sounds soft and weak.
• Hoarseness (or hoarse voice quality) means the voice sounds rough, raspy, or strained, often due to irritation or inflammation of the vocal cords.
• Roughness (or rough voice quality) means the voice sounds uneven or harsh, often with irregular vibrations of the vocal folds. This may be due to vocal fold pathology like swelling or nodules. Roughness is similar to hoarseness but may be more pronounced or consistent.
• Harshness (or a harsh voice quality) means the voice sounds like it has a sharp or grating quality. Harshness often occurs when the vocal folds are forced together with too much pressure or tension, leading to an aggressive, abrasive sound. For example, this may be caused by vocal strain.
• Diplophonia occurs when the vocal cords vibrate at two different speeds which results in the production of two distinct pitches simultaneously. This can give the voice a “double” sound.
• Vocal fry is when the voice drops to a low pitch and produces a creaky, crackling sound. It happens when the vocal cords are held loosely together and vibrate slowly, creating a low, gravelly sound. Fry is often used stylistically in speech and has become socially acceptable thanks to a number of social media influencers.
• Tremor in the voice is an involuntary, rhythmic variation in pitch or loudness. It can sound like a shaking or quivering voice. Tremor is often associated with neurological conditions (e.g., Parkinson’s disease) but can also result from anxiety or fatigue.

(Colton et al., 2011; Gillam & Marquardt, 2016)

Causes of voice disorders

Voice disorders (or dysphonias) can occur across the lifespan due to a range of reasons.  For example:

• people who experience neurological or spinal cord injury that affects the cranial nerves that innervate muscles for voice production (e.g. Vagus nerve [cranial nerve X]);
• people who experience head and/or neck cancer and who require surgery and/or chemoradiation;
• people who have a pathology or non-cancerous lesion (e.g. laryngitis, vocal nodules, vocal polyps) that affects vibration of the vocal folds;
• occupational voice users who may experience short or longer term voice difficulties due to voice overuse or misuse (e.g. teachers, vocal performers, media presenters, sports referees, athletes; children who frequently yell or scream).

Categories or classifications of voice disorders

When categorising or classifying voice disorders, this is typically done by exploring and analysing the aetiology (or cause) of the voice disorder.  Below are examples of some of the common aetiology-based classifications of voice disorders: