Consonant articulation acoustics and intelligibility in Swedish speakers with Parkinson’s disease: a pilot study

Figures & data

Table 1. Group characteristics.

	Speakers with Parkinson’s disease (n = 11)			Healthy speakers (n = 6)
	M	SD	Range	M	SD	Range	Group comparisons^a
Age	71	6.84	61–82	71	6.65	62–78	U = 37; p = 0.733
MMSE-score^b	28	1.57	26–30	29	0.95	28–30	U = 41.5; p = 0.404
Intelligibility (%)^c	79	15	52–95	95	5	86–98	U = 60; p = 0.005
Time since diagnosis (yrs)	7	3.86	1–11	n/a
Gender	4 F/7 M			3 F/3 M
Hearing impairment/use of hearing aids	4/2			2/1

^aMann Whitney U

^bMaximum possible score = 30

^cpooled percentage of scores from transcription of sentences from picture description and the Swedish Test of Intelligibility (STI; Hartelius, 2015)

Table 2. Overview of acoustic measures.

Speech component	Speech material	Measure
Consonant articulation	Word initial consonant clusters /spr/, /str/, and /skr/ extracted from orally read sentences	Spectrogram ratings on six-point scale^a
Alternating motion rate (AMR)	Syllable repetition (/pa/; /ta/; /ka/)	Syllables/sec
Intersyllabic variation of duration in AMR tasks	Syllable repetition (/pa/, /ta/, and /ka/)	Intersyllabic variation quotient (IVQ)^b
Sequential motion rate (SMR)	Syllable repetition (/pa-ta-ka/)	Syllables/sec
Intersyllabic variation of duration in SMR task	Syllable repetition (/pa-ta-ka/)	Intersyllabic variation quotient (IVQ)^b
Voice onset time (VOT)	Syllable repetition (/pa/, /ta/, and /ka/)	Time (ms) between stop release and onset of voicing
VOT ratio	Syllable repetition (/pa/,/ta/, and/ka/)	VOT (ms)/syllable duration (ms)
Voice onset time variability	Syllable repetition (/pa/, /ta/, and /ka/)	Intraspeaker standard deviation of VOT

^a0 = speech sound/cluster looks very non-typical; speech sound is impossible to differentiate from neighbouring sounds or is completely missing; 5 = speech sound/cluster looks very typical and speech sounds can very easily be differentiated from neighbouring sounds.

^bIVQ = SD_{SYLL DUR}/average syllable duration

Table 3. Inter- and intra-rater reliability for spectrogram ratings of consonant clusters: Intraclass correlations (ICC).

	Inter-rater reliability^a		Intra-rater reliability^b
	All speakers (n = 17)	Speakers with PD (n = 11)	All speakers (n = 17)	Speakers with PD (n = 11)
/spr/^c	0.880	0.842	0.836	0.903
/s/^d	0.867	0.874	0.776	0.832
/p/^d	0.915	0.932	0.643	0.766
/r/^d	0.833	0.712	0.834	0.854
/str/^c	0.830	0.814	0.765	0.908
/s/^d	0.705	0.800	0.804	0.936
/t/^d	0.850	0.848	0.818	0.815
/r/^d	0.708	0.743	0.714	0.787
/skr/^c	0.881	0.869	0.928	0.965
/s/^d	0.774	0.723	0.844	0.882
/k/^d	0.914	0.910	0.905	0.907
/r/^d	0.875	0.849	0.915	0.897

^aInter-rater reliability: Intraclass correlation coefficients (ICC) were calculated based on a mean-rating, absolute agreement, two-way random-effects model.

^bIntra-rater reliability: Intraclass correlation coefficients (ICC) were calculated based on a single rater, absolute agreement, two-way mixed-effects model.

^cRatings of whole cluster on a six-point scale (0 = cluster looks very non-typical, none of the speech sounds are possible to differentiate from neighbouring sounds to 5 = cluster looks very typical, all speech sounds are very easily discernible with clear transitions between them)

^dRatings of individual speech sounds on a six-point scale (0 = speech sound looks very non-typical, is impossible to differentiate from neighbouring sounds or is completely missing to 5 = speech sound looks very typical and can very easily be differentiated from neighbouring sounds)

Table 4. Percentage inter-judge agreement for spectrogram ratings of consonant clusters.

	Speakers with PD (n = 11)		Healthy speakers (n = 6)
	% agreement exact values	% agreement ± 1 scalepoint	% agreement exact values	% agreement ± 1 scalepoint
/spr/^a	28	68	51	89
/s/^b	36	79	52	86
/p/^b	36	73	50	84
/r/^b	16	56	46	78
/str/^a	32	70	37	79
/s/^b	30	62	41	79
/t/^b	36	64	39	59
/r/^b	29	64	31	64
/skr/^a	28	70	31	82
/s/^b	38	75	44	84
/k/^b	29	71	34	80
/r/^b	26	58	40	76

^aRatings of whole cluster on a six-point scale (0 = cluster looks very non-typical, none of the speech sounds are possible to differentiate from neighbouring sounds to 5 = cluster looks very typical, all speech sounds are very easily discernible with clear transitions between them)

^bRatings of individual speech sounds on a six-point scale (0 = speech sound looks very non-typical, is impossible to differentiate from neighbouring sounds or is completely missing to 5 = speech sound looks very typical and can very easily be differentiated from neighbouring sounds)

Figure 1. Ratings of consonant clusters /spr/, /str/, and /skr/ in waveform diagrams and spectrograms for individual speakers with Parkinson’s disease (Sp1-Sp11, grey bars) and for groups (speakers with Parkinson’s disease (PD) and healthy speakers (HS), unfilled bars).

Note. Global ratings of consonant clusters on six-point scale (0 = cluster looks very non-typical, none of the speech sounds are possible to differentiate from neighbouring sounds, to 5 = cluster looks very typical, all speech sounds are very easily discernible with clear transitions between them). Speech material: Words with initial consonant clusters extracted from oral sentence reading. Individual speakers (Sp) are numbered based on intelligibility percentage score, where Sp1 has the lowest score (52%) and Sp11 the highest (95%).* = p < 0.05

Figure 2. Ratings of individual speech sounds in consonant clusters in waveform diagrams and spectrograms on six-point scale for groups of speakers with Parkinson’s disease (PD) and healthy speakers (HS).

Note. Scale endpoints: 0 = speech sound looks very non-typical, speech sound is impossible to differentiate from neighbouring sounds or is completely missing, to 5 = speech sound looks very typical and can very easily be differentiated from neighbouring sounds.* = p < 0.05

Figure 3. Articulatory motion rate (syllables/sec) in syllable repetition for individual speakers with Parkinson’s disease (Sp1-Sp11, grey bars) and for groups (speakers with Parkinson’s disease (PD) and healthy speakers (HS), unfilled bars).

Note. Measure for alternating motion rate (AMR: /pa/, /ta/, /ka/) is the average of 10 and for sequential motion rate (SMR, /pa-ta-ka/) the average of 12 consecutive syllable repetitions.Individual speakers (Sp) are numbered based on intelligibility percentage score, where Sp1 has the lowest score (52%) and Sp11 the highest (95%).* = p < 0.05

Figure 4. Intersyllabic variation of duration in syllable repetition, expressed as intersyllabic variation quotient (IVQ), for individual speakers with Parkinson’s disease (Sp1-Sp11, grey bars) and for groups (speakers with Parkinson’s disease (PD) and healthy speakers (HS), unfilled bars).

Note. IVQ = SD_{SYLL DUR}/average syllable duration. Measures for alternating motion rate (AMR: /pa/, /ta/, /ka/) are average of 10 and for sequential motion rate (SMR, /pa-ta-ka/) average of 12 consecutive syllable repetitions. Individual speakers (Sp) are numbered based on intelligibility percentage score, where Sp1 has the lowest score (52%) and Sp11 the highest (95%).* = p < 0.05, ** = p < 0.01

Figure 5. Voice onset time (ms) in syllable repetition for individual speakers with Parkinson’s disease (Sp1-Sp11, grey bars) and for groups (speakers with Parkinson’s disease (PD) and healthy speakers (HS), unfilled bars).

Note. Measures are mean and standard deviation of voice onset time in 10 consecutive syllables from AMR tasks (repetition of /pa/, /ta/, and /ka/). Average number of measurable syllables for speakers with PD/healthy speakers were 8.09/9.83 for /pa/, 8.09/9.67 for /ta/, and 6.45/10.00 for /ka/. Individual speakers (Sp) are numbered based on total pooled intelligibility percentage score, where Sp1 has the lowest score (52%) and Sp11 the highest (95%).* = p < 0.05, ** = p < 0.01

Table 5. Correlations between acoustic measures and intelligibility for speakers with Parkinson’s disease (n = 11).

Speech component	Variable	Correlation with intelligibility^a
Consonant articulation (rating of whole cluster)	/spr/ /str/ /skr/	0.721* 0.706* 0.797**
Alternating motion rate (AMR)	/pa/ /ta/ /ka/	0.338 0.304 0.451
Intersyllabic variation of alternating motion rate (AMRvar)	/pa/ /ta/ /ka/	−0.456 −0.083 −0.185
Sequential motion rate (SMR)	/pa-ta-ka/	0.402
Intersyllabic variation of sequential motion rate (SMRvar)	/pa-ta-ka/	−0.187
Voice onset time (VOT)	/pa/ /ta/ /ka/	−0.509 −0.538 0.373
Voice onset time variability (VOTvar)	/pa/ /ta/ /ka/	−0.668* −0.207 0.188
Weighted deviation score^b	Pooled deviation^b from healthy speakers for all variables	−0.749**

^aSpearman rank order correlation, * = p < 0.05; ** = p < 0.01

^b > 1 SD from healthy speaker mean = score 1; > 2 SD from healthy speaker mean = score 2

Hartelius, L. (2015). Dysartri - bedömning och intervention [Dysarthria - assessment and intervention]. Studentlitteratur.

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