(2) Chapter 7 - Vocal Pitch, Loudness, and Quality

Voice and its Disorders

pitch

The vocal folds vibrate to make sound for voice; during vibration, vocal folds have a closed phase and an open phase which equals one cycle of vibration

The perceptual correlate of frequency and is typically described as how high or low the voice sounds; largely based on the frequency of vocal fold vibration as is called fundamental frequency

Speaking fundamental frequency is generally considered an individual's habitual or typical speaking pitch

Determined by mass, tension, and elasticity of the vocal folds

Higher pitch results when the vocal folds are thinner, more tense, or both; lower pitch results when the folds are thicker, more relaxed, or both

Frequency can stay constant and pitch can change by changing the size or length of the resonating cavity, the vocal tract; a smaller resonating tube will be perceived as a higher pitch

Frequency perturbation (jitter)

frequency

The number of cycles per second

The rate at which the vocal folds vibrate

Higher frequencies have more cycles per second than lower frequencies

frequency perturbation (jitter)

Refers to irregularities or cycle-to-cycle variations in vocal fold vibration that are often heard in dysphonic patients

Can be measured instrumentally as a patient sustains a vowel

Patients with voice problems, such as tremor or hoarseness, might show a large amount of jitter

People with no laryngeal pathology are able to sustain a vowel with less than 1% jitter

Measures of jitter have been used in voice assessment because they can be useful in early detection of vocal pathology, though their utility is often debated

loudness

The perceptual correlate of intensity

Determined by the amplitude of the sound signal; the larger the amplitude of vibration, the more intense the sound signal, the greater its perceived loudness

Changes in air pressure created during vocal fold vibration displaces air particles; a chain reaction of air particle disturbance creates a sound wave; force determines the extent to which air particles are displaced from their resting state to a maximum point of displacement

Amplitude perturbation (shimmer)

amplitude

The magnitude of particle displacement

The greater the amplitude, the louder the voice

amplitude perturbation (shimmer)

Refers to the cycle-to-cycle variations in vocal fold amplitude

It can be measured instrumentally as a patient sustains a vowel

A speaker with no laryngeal pathology should have a very small amount of amplitude perturbation with each vibratory cycle

Some experts believe that more than 1 dB of variation across cycles makes a patient sound dysphonic

Patients who have difficulties with regularity of vocal fold vibration (e.g., roughness) might show large amounts of shimmer

Measures of shimmer have been used in voice assessment because they can be useful in early detection of vocal pathology, though their utility is often debated

quality

The perception of the sound of an individual's voice

The determination of voice quality is frequently subjective and is often based on the degree of clarity, breathiness, strain, loudness, pitch, and regularity in vibration of the voice

Types of vocal quality:

• Hoarseness

• Harshness

• Strain-strangle

• Breathiness

• Glottal fry/vocal fry

• Diplophonia

• Stridency

hoarseness

Shows a combination of breathiness and harshness, which results from irregular vocal fold vibrations

Often sound breathy, low pitched, and husky

There may also be pitch breaks and excessive throat clearing

harshness

Described as rough, unpleasant, and "gravelly" sounding

It is associated with excessive muscular tension and effort

The vocal folds are adducted too tightly, and the air is then released too abruptly

strain-strangle

Phonation is effortful, and the patient sounds as if she is "squeezing" the voice at the glottal level

Initiating and sustaining phonation are both difficult

Talking fatigues such patients, and they experience much tension when they speak

breathiness

Results from the vocal folds being slightly open, or not firmly approximated, during phonation

Air escapes through the glottis and adds noise to the sound produced by the vocal folds

May be due to organic (physical) or nonorganic (nonphysical, or functional) causes

Patients often complain that they feel like they are running out of air

Often quiet, with little variation in loudness

Patients frequently show restricted vocal range

glottal fry/vocal fry

Heard when the vocal folds vibrate very slowly with no clear, regular pattern of vibration; the resulting sound occurs in slow but discrete bursts and is of extremely low pitch’ the voice sounds "crackly”

May be the vibratory cycle we use near the bottom of our normal pitch range; typically, it is produced near the end of a long phrase or sentence when air flow rate and subglottal air pressure are both low and lung volume is less

For some patients, use of vocal fry may help modify vocal quality problems, such as stridency; other patients work to eliminate vocal fry by slightly increasing subglottal air pressure and slightly elevating their pitch level

diplophonia

Means "double voice”

It occurs when a listener can simultaneously perceive two distinct pitches during phonation

Usually occurs when the vocal folds vibrate at different frequencies due to differing degrees of mass or tension

A client with a unilateral polyp, for example, might sound diplophonic

stridency

Sounds shrill, unpleasant, somewhat high pitched, and "tinny”

Physiologically, this is often caused by hypertonicity or tension of the pharyngeal constrictors and elevation of the larynx

Tense patients may sound strident