APRAXIA OF SPEECH
Variable errors, noticeable over repeated production of words
Self correction and awareness of errors
Intrusive schwas
Syllable segmentation and syllable lengthening
Slow rate and abnormal prosody
SPEECH BASICS
Pitch: Frequency of the fundamental harmonic. The pitch is determined by the vibration of vocal cords. The pitch of female speakers being on the average twice as high as that of male speakers.
Timbre: Relative height of the frequency of speech in the power spectrum
Loudness: Overall height of peeks in power spectrum.
Prosody: Variation in loudness, pitch, and timing accompanying natural speech. This is measured by F0 SD: Standard deviation of fundamental frequency (F0), representing the variations of vibration rate of vocal folds.
Jitter: this is the measure of the variability of the speech fundamental frequency (pitch period) from one cycle to the next.
Shimmer: This is the measure of amplitude variability within each vocal cycle. Jitter and shimmer are measures for assessing the micro-instability of vocal fold vibration.
Formant: Formants distinguish one vowel from the other. Formants are produced by vocal tract resonances and their frequency depends on position of the tongue with respect to palate.
Consonant classification:
1. Plosive or stop (p, t, k) - produced by blocking the flow of air.
2. Fricative (f, s, sh, h, v) – These are produced by making the airflow constricted to create turbulence.
3. Nasal (m, n) – produced by lowering the soft palate
4. Liquid (l, r) – produced by raising tip of tongue.
Diadochokinetic (DDK) task:
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Alternating Motion Rate (AMR) involves a single syllable being repeated at maximum rate. Syllables pa, ta, ka are used individually for AMR.
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Sequential Motion Rate (SMR) involves a sequence of syllables is repeated at maximum rate. ‘pataka’ is used for SMR.
Syllables are repeated at a constant rate and long as possible (at least five times). They have been shown to correlate with perceptual ratings of severity and intelligibility in dysarthria. A single trial may be sufficient, as DDK tasks have high test-retest reliability.
Harmonic to noise ratio (HNR): HNR is a measure of quality of speech. Harmonics-to- noise (HNR) ratios are derived from the signal-to-noise estimates from the autocorrelation of each cycle and are used for assessing voice hoarseness. Low HNR (<20DB) is suggestive of a hoarse voice.
Pulse: Pulse is one opening and closing cycle of vocal cord.
Number of voice breaks: Over all count of voice breaks. Defined as distance between consecutive pulses longer than 1.25 divided by bottom of the pitch range. (if the pitch bottom is 100 hz then it would be 1.25 x 1/100 = 1.25 x 10 msec = 12.5 msec. ie the next pulse was delayed by 2.5 msec)
Degree of voicelessness (DUV): DUV is a measure of breaks in the sustained phonation. Spastic voice has a strained and strangled quality and is usually associated with effortful squeezing of air during passing through glottis. The strained-strangled voice is assumed to arise from over closure of vocal folds during the production of vowels and can be measured by the parameter DUV. Similarly in ataxic speech increased DUV or pitch breaks are commonly seen. DUV are the fraction of pitch frames that are analyzed as unvoiced. It is measured by sustained phonation
HYPOKINETIC SPEECH
Reduced Prosody (Monopitch)
Low volume
Tachyphemia: Delayed Auditory Feedback (DAF) and metronome may help in reducing he rate of speech
Speech analysis:
Airflow insufficiency (Maximum phonation time (MPT))
Harsh voice (Jitter, shimmer and HNR)
Rapid AMR (DDK rate)
Reduced loudness (Mean speech intensity in monologue)
Monopitch (F0 SD) in Monologue
F0 (Pitch) Curve: In PD there is loss of F0 rise and peaks and flatting of f0 curve.
DYSTONIA OF SPEECH
Adductor dystonia
85% of cases of vocal cord dystonia
breaks due to hyper-adduction of vocal cords resulting in a quick glottic closure interrupting airflow
Use sentences that have several glottal stops (rapid onset of voice)
Use voiced sentences:
" We eat eels everyday'
"We mow our lawn all year"
"We eat eggs ever Easter"
Abductor dystonia
Breathy effortful voice with abrupt breaks
whispering elements of speech due to prolonged abduction during voiceless consonants (/h/,/s/,/f/,/p/,/t/,/k/).
Use sentence:
"The puppy bit the tape"
ATAXIC SPEECH
Excess and equal stress on syllables
Irregular articulatory breakdown
Prolonged phonemes (Scanning speech)
Speech analysis:
Excess pitch fluctuations in sustained phonation (F0 SD)
Vocal tremor
Irregular AMR
Prolonged phonemes
Excess intensity variations in monologue (Intensity SD)
F0 (Pitch)Curve: Ataxic speech demonstrates breaks in F0 curve.
SPASTIC SPEECH
Bilateral UMN lesions
Strained-strangled voice
Slow AMR
Slow speech rate
Low pitch voice
Speech analysis:
Normal HNR (Harmonic to Noise Ratio)
High Jitter and Shimmer
High pitch variability
Strained-strangled voice (DUV)
Slow AMR (DDK rate)
Slow speech rate (words/ sec)
FLACCID SPEECH
Breathy voice (Adductor weakness)
Breathiness is noise quantified by HNR
Audible respiration
Patient uses short phrases
Mono loudness and Mono pitch
May have Diplophonia ( Double pitch)
Usually seen in unilateral vocal cord palsy
AMR is usually normal to fast
Hyper nasal voice:
More low frequencies as high frequencies are filtered
PaPaPa or BaBaBa sound like NaNaNa or MaMaMA
Speech analysis:
High HNR (Harmonic to Noise Ratio)
Normal Jitter and Shimmer
Diplophonia
Airflow insufficiency (Maximum phonation time (MPT))
TREMOR
Vocal cord, jaw, tongue, lip or respiratory muscle tremor.
In a patient with diffuse cerebellar atrophy and presenting with audible voice tremor, Fundamental frequency contours during sustained phonation of vowels showed rhythmic oscillations at a rate of about 3 Hz. This may indicate an impairment of phonatory control by maintaining a constant isometric activity of the internal laryngeal muscles.
Method:
Speech testing included sustained phonation on /u/ and /a/ or sustained production of voiceless fricatives /f/, /sh/, /s/ as long as possible on a single breath
Vowel production tasks examine the patient's faculty of maintaining a stable laryngeal configuration
Fricative task requires the maintenance of stable articulatory configurations of lips and jaw (/f/), tongue blade and jaw (/s/), and tongue dorsum and jaw (/sh/), respectively.
In both tasks, a constant transglottal flow must be maintained through respiratory control. Respiratory muscle will be present in all above tasks.