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Immediate Effect of Alcohol on Voice Tremor Parameters and Speech Motor Control.

Intoxication is a state that occurs after the intake of a high dosage of intoxicating substances such as drugs and alcohol. The effect of alcohol intoxication on health and wealth is not unknown to many but this does not stop many of its consumers from its intake. The increased incidence of crime for obtaining alcohol and post alcohol intake pays off for the lax benefits obtained by the government. However, controlled intake of alcohol is said to have medicinal benefits for the reduction of cholesterol and reducing peripheral vascular disorders and coronary heart disease (Camarco et.al., 1997; Doll, Peto, Hall, Wheatley & Gray, 1994; Keil, Chambless, Doring, Filipiak & Stieber, 1997; Kitamura et.al., 1998, Rehm, Bondy, Sempos, & Vijonc, 1997). But where this 'line of limit' is to be drawn is not clear. This limit should be the safe amount of blood alcohol concentration that has no or minimum effect on the normal body functions. Every country has set their permissible alcohol levels for safe driving which are usually detected using a breath analyzer which has error rates varying from 15-23% (http://en.wikipedia.org/wiki/Breathalyzer). This study is an attempt to understand the effect of 0.08% alcohol concentration on acoustic parameters of repetition of syllables and sustained phonation immediately after its absorption into the blood stream.

The effect of long term intake of high dosage of alcohol on health has been the trend in medical and psychological research over many decades. Many shocking reports of health and wealth issues have emerged from these studies (Drug and alcohol services South Australia, 2010). But the most immediate and overt symptoms of alcohol intoxication are the changes in speech, language and motor characteristics of an intoxicated individual. The alcohol interferes with the normal functioning of cerebellum and leaves the individual in an excited state of body and mind leading to uninhibited speech and thoughts which are sometimes socially and culturally inappropriate. The effect of alcohol intoxication on communication behaviour (llouck & Moyers, 2015), language formulation (Alexandrov, Sams, Lavikainen, Reinikainen & Naatanen, 1998; Andrews, Cox & Smith, 1977; Jaaskelainen et.al., 1995; Natale, Klanzer, Jaffe & Jaffe, 1980; Pisoni & Martin, 1989) and motor skills (Knapp, 2006) is well known. Speech being a complex interplay of fine motor control within and across speech systems may be one of the first to reveal alcohol intoxication. Superficially, slurred speech is a reliable indication of alcohol intoxication (Van Wyden, online article). Recent literature on the relation between alcohol and speech characteristics has yielded inconclusive results (Table 1).

From the literature, some but varied effects of alcohol intoxication on speech parameters are confirmed and these effects are identifiable, measurable and reliable if variables are controlled. If the various levels of intoxication can produce a specific set of changes in speech, the reverse can be estimated and a model for estimating levels of intoxication from speech samples can be developed. This can then be a reliable and non-invasive substitute to estimate levels of intoxication for purposes of law enforcement. The study by Lee, Bae and Bae (2015) and Lee and Bae, (2016) was conducted in similar directions using phonation samples. But very few studies in literature have controlled the level of intoxication for studying the changes in speech parameters in their subjects. Oueller and Hamsberger (2010) studied the vowel space, speaking rate and fundamental frequency measures with increasing levels of alcohol intoxication.

Toward Surreptitious Remote Sensing of Blood Alcohol Concentration: Results with Integrated Near-Infrared Spectral Imaging and Laser Speech Detection.

To date, the published reports suggest that the effect of alcohol on the acoustic parameter of speech is variable due to the modest amount of research on possible intoxication-speech relationships. Previous research has also shown the importance of setting strict dosage, using the same subjects throughout all procedures and rigorously controlling intoxication levels, recording speech samples in a precise manner each time, making precise speech measurements, managing strict control over participant selection and the use of technology to make measurements (Chin & Pisoni, 1997; Pisoni, Hathaway & Yuchtman, 1985). Thus, there is a need to replicate the study of parameters of speech on a selected set of participants following intake of a standard dose of alcohol with the advantages of the latest digital technology. This study was aimed at this direction by studying the effect of a pre-determined level of alcohol intoxication on speech motor control and voice tremor parameters as assessed using an automated protocol. The specific objective of the study was to compare the performance of participants on measures of Diadochokinesis, Voice Tremor and Formant Transition before and after a pre-determined level of intoxication.

METHOD

Participants

A total of 38 individuals who consume alcohol were interviewed for their habitual drinking habits. They were included in the participant list if they satisfied the following inclusion criteria:

1. Consume alcohol at least once in a week

2. No neuro-muscular or cognitive communication disorders reported

3. Willing to participate in the study

Participants were excluded if the habitual beer dosage was less than the required alcohol dosage (Detailed in the procedure section below) or if they consumed more dosage of alcohol than the required alcohol dosage. If otherwise, the participants were enrolled into the study procedure.

A total of 10 males of 20-30 years of age satisfied the inclusion and exclusion criteria participated voluntarily in the study. All participants were explained the procedure of the study after which consent was taken for their participation.

Materials Used

1. An Olympus WS-400S DNS Digital Voice Recorder for recording the data sample.

2. Omron HN-286 digital weighing machine for body weight measure of participants.

3. Computerized Speech Lab 4500 with its module Motor Speech Profile (Kay Pentax, USA) loaded onto a desktop for obtaining the speech-motor measures and voice tremor measures of the data sample in a laboratory setting.

Procedure

The body weight of each participant was measured using a digital weighing machine (Omron HN-286) and the amount of beer intake required for an intermediate level of intoxication, i.e. 0.80g/kg of Blood Alcohol Level (Bauer, Schumock, Horn & Ophcim, 1992; Hollien, Hamsberger, Martin, Hill & Alderman, 2009; Nagoshi & Wilson, 1989) calculated using Widmark's formula as given below:

BAL (%) = mass of alcohol (g) / [reduction factor (0.73 for men) * body weight(kg)].

Each participant was given three tasks to perform before and after alcohol intoxication: (1) diadochokinesis [repeated utterance of/pa/, /ta/, and /ka/(AMR) and repeated utterance of /ptk/ in the maximum rate possible (SMR tasks)] (2) Sustained phonation [sustained phonation of /a/] and (3) Formant transition task [repeated utterance of/i-u-i/]. Three trials of each task were recorded from each participant before and after alcohol intoxication on a portable digital voice recorder (Olympus WS-400S DNS Digital Voice Recorder). The data were recorded and stored for later analysis at a laboratory setting using Motor Speech Profile (Computerized Speech Lab 4500, Kay Pentax, USA).

Analysis

The specific protocols for Diadochokinesis, Voice tremor and Formant Transition Protocols of Motor Speech Profile (MSP) were run on the data. The protocol specific analysis procedure followed for the study is detailed below:

1. Diadochokinesis protocol:

The recorded data on Didochokinesis task was opened on the Motor Speech Profile Platform with a threshold of detection at 55dB. The protocol was run and the detected DDK peaks were visually verified. If less than 90% of peaks were detected, the threshold was raised higher until the 90% level was obtained. The DDK rate, period, consistency and accuracy measures were obtained and tabulated for statistical analysis.

2. Voice Tremor Protocol:

The recorded sustained phonation data were opened on the Motor Speech Profile Platform. The waveform was inspected for stable amplitude and an 8-sec data with good amplitude was trimmed for analysis. The protocol on voice tremor was run on the trimmed data and measures were tabulated for statistical analysis.

3. Formant Transition Protocol:

The recorded data on formant transition (repetition of /i-u/) was opened on the Motor Speech Profile Platform. The waveform was inspected for amplitude level and an 8-sec data with good amplitude was trimmed for analysis. The protocol on formant transition was run on the trimmed data with a filter setting set per manufacturer's guideline. However, the protocol could not be completed due to breaks and low signal to noise ratio. This protocol was eliminated from the study due to high error rates.

RESULTS AND DISCUSSION

The present study was aimed at comparing the Diadochokinesis (DDK), voice tremor (VT) and formant transition (FT) measures obtained from participants before and after alcohol intoxication. Due to technical issues, the forniant transition protocol had to be eliminated from the data sample. Thus, the statistical analysis was run only on DDK and VT measures. The tabulated data on DDK and VT measures were subjected to descriptive statistical analysis for obtaining the mean and standard deviation of DDK and VT measures (Table 2).

From Table 2, a general trend of change in measures of DDK and VT, pre- and post-intoxication could be observed. The DDKavp decreased or remained comparatively stable post intoxication for AMR tasks but increased for SMR tasks. But DDKavr did not show significant change post-intoxication in AMR and SMR DDK tasks. The other measures of DDK such as DDKcvp and DDKcvi decreased post-intoxication. Interestingly, the standard deviation of DDK measures tend to decrease post-intoxication. In VT measures, v[F.sub.0] showed a significant increase post intoxication. Other measures of VT remained stable across the two conditions.

To understand the descriptive data further and to study the changes in DDK and VT measures pre-and post-intoxication in the participants, the data were subjected to non-parametric statistical analysis using Wilcoxon's Sign Rank test. Further, a Friedman test was run to understand the differences in performance across tasks in the pre- and post-intoxication tasks. The result of this statistical comparison is presented and discussed below under the following sections:

Effect of intoxication on rate and consistency Measures of DDK:

Wilcoxon's Sign Rank test revealed significant differences in the DDKavp (Z= 3.557, p < 0.05) and DDKavr (Z= -3.207, p < 0.05) for repetition of the syllable /p/ but not /t/, /k/ or /ptk/. The DDKavp decreased and the DDK avr increased for the repetition of /pa/ post-intoxication. There was no statistically significant effect of intoxication on DDKcvp, DDKjit and DDKcvi for repetition of /t/, /k/ or /ptk/ or alternate motion for /ta/, and /ka/. Interestingly, there was no significant difference in the DDK measures for sequential movement for /ptk/ before and after alcohol intoxication.

The Friedman test run across tasks in the pre-intoxicated and post-intoxicated conditions revealed mixed results. Statistically, significant differences were obtained for DDKavp ([chi square](3) = 8.99, /; < 0.05), DDKavr ([chi square](3) = 6.01, p < 0.05) and DDKjit ([chi square](3) = 14.95, p < 0.05) in the pre-intoxicated condition. Similarly DDKavp and DDKjit showed statistically significant changes post-intoxication also ([chi square](3) = 4.08, p < 0.05; [chi square](3) = 3.787, p < 0.05 respectively) few other DDK measures such as DDKcvp ([chi square](3) = 3.495, p < 0.05) and DDKcvi ([chi square](3) = 3.57, p < 0.05) showed significant differences post-intoxication. A post(add "-")hoc analysis revealed that the average DDK period for /pa/ was significantly different from /ka/ before and after alcohol intoxication but the significant difference that existed between /pa/ and /ta/ before intoxication was absent after intoxication. The Average DDK period of /pa/ was reduced to that of /ta/ suggesting an increased rate of repetition of /pa/ following intoxication. A similar change was noticed in the measure of DDKjit which measures cycle to cycle variation in a period of DDK. The cycle to cycle variation of period in production of /pa/ increased to that of /ta/ following intoxication.

The rapid production of the bilabial syllable /pa/ may suggest an excitatory effect of alcohol on speech. An increase in the cycle to cycle variation of period suggests the reduced ability of individuals to maintain stable CV combinations probably due to the effect of alcohol on the central speech motor control system. The increased rate of CV production may be achieved by the compromised precision of articulatory movements but this needs to be established with further research.

It is interesting to learn that the syllable /pa/ is more affected by alcohol intoxication than the syllables /ta/ and /ka/. This may be related to the mass of the structure that produces these syllables. The tissue mass of lips is greater than the mass of tongue tip that produces /ta/ or a posterior portion of the tongue that produces /ka/ and a greater sensorimotor planning for precise execution of bilabials (Smith, 1978). Alcohol intake may interfere with this planning and can affect the finer control leading to variation in these acoustic parameters.

Though there was an increase in the rate of production of bilabials after alcohol intoxication, this increased rate cannot be generalized to all syllables and in all context. A previous study by Chin, Large and Pisoni (1996-1997) found an increased duration of word segments following alcohol intoxication suggesting a reduced rate of speech. However, their study did not mention the number of word segments that consisted of bilabial sounds in their speech sample.

Effect of intoxication on Measures of Voice Tremor

Wilcoxons Sign Rank test revealed significant difference across the two intoxicated states in the measure of MFTR (Z= -2.240, p = 0.05). None of the other measures revealed significant changes after considerable intoxication. From Table 2, it has been previously observed that the standard deviation of VT measures increased after intoxication, probably indicating a wide individual variability in the performance of the task. This might have interfered with proving the observation statistically for difference in performance, post alcoholic intoxication. The Friedman test and post-hoc was not run on the data as the data included only one task in two intoxicated conditions.

The magnitude of frequency tremor increased after alcohol intoxication. This measure suggests the ability of a person to maintain a constant fundamental frequency during every cycle of vocal fold vibration. An increased MFTR suggests the effect of alcohol intoxication on the laryngeal control for stable sustained phonation. There are some supporting studies that states that lower alcohol levels can affect laryngeal physiology (Klingholtz et.al., 1988). Studies using high speech motion pictures have found counter motion of mucous membrane in intoxicated subjects. A physiological reason behind this incoordination between cycles of vocal vibration may be the effect of alcohol on the cerebellar processes that control laryngeal behaviors. However, a lowering of [F.sub.0] that was revealed in their study could not be replicated here. A higher standard deviation of F0 in the post alcoholic condition may have masked this difference statistically. However, the periodicity of tremor could not be derived due to technical reasons. Increased standard deviation of acoustic measures post alcohol intoxication suggests that the effects of alcohol on the acoustic parameters of speech are variable. This calls for further research in this area for understanding the effect of various amounts of Blood Alcohol Level on acoustic parameters of speech taking into account the inter subject variability in the susceptibility to effects of alcohol intoxication.

Overall, the effect of blood alcohol level of 0.80g/kg which is the permissible limit of intoxication for legal traffic in USA made the acoustic measures of speech susceptible to changes. In India, this limit is lower (0.30g/ kg). From the present study, changes in motor control for articulator movement and voice production was indicated. This opens a new arena of research towards understanding the effect of various levels of alcohol on speech performance and its application on detecting levels of blood alcohol level without invasive methods. If such speech patterns could be derived, a new non-invasive model for alcohol level that substitutes the present methods of blood alcohol/ breath alcohol estimation methods can be developed. A replication of this study with a larger sample size, various levels of BAL and a larger number of acoustic variables is demanded and is being undertaken by the investigators.

Correspondence concerning this article should be addressed to: Ms. Gayathri Krishnan, Clinical Assistant, All India Institute of Speech and Hearing, Mysuru, Karnataka, India; Email: gayathrikrishnan.india@gmail.com.

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Gayathri Krishnan All India Institute of Speech and Hearing

&

Vipin Ghosh P. G. JSS Institute of Speech & Hearing
TABLE 1.
Summary of Findings in Studies on Various Parameters of Speech
Following Alcohol Intoxication.

Behavioural measures

Speech abnormalities in            Jetter, (1938)
intoxicated subjects

Increased latency of               Andrews, Cox and Smith, 1977; Dodge
performance of intoxicated         and Benedict, 1915; Hollingworth,
participants                       1923; Moskowitz and Roth, 1971;
                                   Sobell and Sobell, 1972; Sobell,
                                   Sobell and Coleman, 1982.

Fluency measures

Moderate to high doses             Andrew, Cox and Smith, 1977; Lester
of alcohol intake leads to         and Skousen, 1974; Klingholz,
dysfluency in speech.              Penning and Liebhardt, 1988; Pisoni
                                   and Martin, 1989

Articulatory measures

Misarticulations of /r/, /l/ and   Chin and Pisoni, 1997; Johnson,
/s/; incomplete articulations      Pisoni and Bernacki, 1989
final devoicing

Prosodic measures

Reduced speaking rate, lower       Chin and Pisoni, 1997, DeJong,
[F.sub.0] and increased [F.sub.0]  Hollien, Martin and Alderman, 1995;
jitter, Increased duration of      Johnson, Pisoni and Bernacki, 1989;
segments                           Ouellet & Harnsberger, 2010

Acoustic measures

Lowering of Fl and F2              Behne and Rivera, 1990

Increased [F.sub.0], preserved     Ouellett & Harnsberger, 2010
vowel space, varied formants       Fairbairn et.al., 2015.
Overall volume

TABLE 2.
Mean (Standard Deviation) of DDK and VT Measures Pre- and Post-Alcohol
Intoxication.


Measures     Unit of      Pre-Intoxication  Post-intoxication
Obtained     measurement

DDK-/p/
DDKavp       ms           284.89 (104.44)   158.17 (30.94)
DDKavr       s              4.29 (1.53)       6.28 (1.16)
DDKcvp       %             72.04 (33.54)     60.10 (36.49)
DDKjit       %             18.51 (9.70)      35.36 (22.85)
DDKcvi       %             20.52 (32.09)      5.87 (3.86)
DDK-/t/
DDKavp       ms           178.69 (45.48)    179.23 (25.93)
DDKavr       s              5.70 (1.43)       5.70 (0.87)
DDKcvp       %             84.19 (57.04)     55.08 (29.74)
DDKjit       %             47.83 (21.83)     31.57 (18.20)
DDKcvi       %              6.67 (4.95)       4.88 (3.17)
DDK-/k/
DDKavp       ms           179.03 (13.53)    175.83 (24.61)
DDKavr       s              5.50 (0.47)       5.72 (0.86)
DDKcvp       %             85.04 (36.31)     56.38 (27.50)
DDKjit       %             46.76 (17.88)     31.32(12.91)
DDKcvi       %              6.82 (3.67)       5.05 (3.37)
DDK-/ptk/
DDKavp       ms           156.13 (32.88)    173.07 (60.88)
DDKavr       s              6.57 (1.49)       6.41 (2.10)
DDKcvp       %            148.43 (210.47)    93.11 (44.44)
DDKjit       %             57.00 (14.17)     51.92 (12.70)
DDKcvi       %              8.88 (4.48)       8.73 (3.63)
VT Measures
[F.sub.0]    Hz           132.14 (7.52)     133.62 (13.83)
v[F.sub.0]   %              1.79 (1.98)       5.82 (14.47)
Fhi          Hz           132.84 (14. 64)   142.46 (20.10)
Flo          Hz           128.84 (7.28)     128.62 (12.80)
vAm          %             11.67 (3.54)      10.82 (3.92)
MFTR         %              0.41 (0.12)       0.51 (0.20)
RATR         Hz             5.57 (1.99)       4.55 (1.12)

Note: DDKavp=Average Period of DDK; DDKavr= Average rate ot DDK;
DDKcvp= Coefficient of variation of DDK period; DDKjit= Jitter of DDK;
DDKcvi= Coefficient of variation in intensity; [F.sub.0] = Fundamental
frequency; v[F.sub.0] = Variation in [F.sub.0]; Fhi= Highest [F.sub.0];
Flo= Lowest [F.sub.0]; vAm= Variation in Amplitude of the signal; MFTR=
Magnitude of Frequency Tremor; RATR: Rate of Amplitude Tremor)
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Author:Krishnan, Gayathri; Ghosh, Vipin P.G.
Publication:Journal of Alcohol & Drug Education
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Date:Aug 1, 2017
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