Examimers:

8 high school girls

Training duration:

1 week

Method:

visual

Speaker population:

123

Number of words:

10 words excerpted from sentences

Context type:

isolated

random context

Temporal sequence:

contemporary

Type of trial:

closed

Total number of trials:

2000

Type of decision:

forced decisions

limited sample

limited time

random context

no aural examination

examiners lacked sufficient experience

Results:

closed trials

range of errors for false ID -

0.35 to 1.0%

10 words excerpted

0.00 to 2.0%

Examimers:

7 PhD candidates in ASC

3 assistant professors in ASC

Training duration:

1 week

Method:

visual

Speaker population:

5 adult males

Number of words:

2 words (you/it) in isolation & excerpted from 4 short sentences

Context type:

1 word in isolation

2 words from random context

Temporal sequence:

contemporary

Type of trial:

closed

Total number of trials:

1046

Type of decision:

forced decisions

limited sample

random context

no aural examination

examiners not trained

Results:

closed trials

range of errors for false ID -

"you" in islation:

10.4 to 18.0%

‘it' in isolation:

22.7 to 33.0%

"you/it" from ramdom context in trial 1 of 15:

mean error: 62.7%

Examimers:

college students

6 in the open trials

4 in the closed trials

Training duration:

1 week

Method:

aural vs.visual but not combined

Speaker population:

24 males

Number of words:

catalogue of 11 words in different random order - only 1 word used in most trials

Context type:

1 to 4 words

Temporal sequence:

non-contemporary

(1 week)

Type of trial:

closed & open

Total number of trials:

216

Type of decision:

forced decisions

limited sample

(1 to 4 words)

random context

no aural examination

examiners not trained

Results:

open trials:

range of errors for false ID for 4 examiners/1 word visual trials -

31.0 to 47.0%

aural trials -

6.0 to 8.0%

closed trials:

range of errors for false ID -

1 - 4 discrete words visual trials

20.0 to 30.0%

aural trials

5.0 to 18.0%

Examimers:1 month

Method:

visual

Speaker population:

250 males randomly selected from a population of 25,000

Number of words:

6 & 9 words

Context type:

isolated, fixed and

random context

Temporal sequence:

contemporary & noncontemporary (1 month)

Type of trial:

closed & open

Total number of trials:

34,992

Type of decision:

forced decisions, but allowed to rate confidence level

limited sample

limited time

no aural examination

examiners lacked sufficient experience

Results:

range of errors for all trials false ID -

0.51 to 6.43%

when only ‘fairly & almost' certain decisions are combined, the error of false ID reduces to 2.4%

Examimers:

college students

(7 panels of 2)

Training duration:

5 lectures and 3 practice sessions

Method:

visual

Speaker population:

60 males

Number of words:

5 words in the same context, 5 words physically excerpted from random conversation

Context type:

fixed and random context

Temporal sequence:

contemporary

Type of trial:

closed & open

Total number of trials:

280

Type of decision:

forced decisions

limited sample (5 words)

no aural examination

random & fixed context

examiners lacked sufficient experience

used the most dissimilar spectrographic utterances

compared sounds from totally different words

studying changing phonetic context

examiners could not evaluate effects of coarticulation due to questionable word boundaries

Results:

closed trials

errors for false ID -

fixed context

range:10.0 to 30.0%

mean: 20.0%

randon context

range:50.0 to 90.0%

mean: 74.29%

open trials

errors for false ID -

fixed context

range:16 to 66%

mean: 42.86%

randon context

range:66 to 100%

mean: 83%

Examimers:

7 police & private

Training duration:

more than 2 years experience/less than 2 years experience

Method:

combined aural and visual

Speaker population:

7 male & female

Number of words:

38 to 54 words

Context type:

fixed context

Temporal sequence:

noncontemporary (1 week)

Type of trial:

open

Total number of trials:

84

Type of decision:

no forced decisions

allowed 1 to 5 conclusions

no limited time

aural & visual examination

trained and experienced examiners

Results:

open trials

trainees w/less than 2 yr eperience:

false ID - 0.0%

false elim. 5.0%

no decision 25.0%

0.35 to 1.0%

examiners w/more than 2 yr eperience:

false ID - 0.0%

false elim. 0.0%

no decision 22.0%

Examimers:

12 scientists, police and private

Training duration:

novice: no training

trainee: < 2 yr

Professional: > 2 yr

Method:

combined visual and visual

Speaker population:

20 male & female

Number of words:

9 words

Context type:

fixed context

Temporal sequence:

noncontemporary

Type of trial:

open

Total number of trials:

120

Type of decision:

no forced decisions

allowed 1 to 5 conclusions

no limited time

aural & visual examination

compared words in context - trainees, novices and experienced examiners

Results:

open trials:

errors novices

false ID 5.0%

false elim 25.0%

no decision 2.5%

trainee

false ID 0.0%

false elim 0.0%

no decision 2.5%

Professional

false ID 0.0%

false elim 0.0%

no decision 7.5%

Examimers:

4 professional and 20 college graduates

Training duration:

IAVI certified voice identification examiner

Method:

combined visual and visual / visual only

Speaker population:

professional minic and 6 celebrity voices

Number of words:

mimic (mean of 25 sec.), celebrities (mean of 35 min.)

Context type:

quasi-fixed and random context

Temporal sequence:

contemporary/ noncontemporary

Type of trial:

open

Total number of trials:

aural (20/examiner)

visual (200/examiner)

Type of decision:

same, different or undecided

5 IAVA classifications

Results:

Interspeaker variability does not exist between a mimiced, disquised voice and the nature voice of the subject mimiced. Intraspeaker variabilities are minute and not signifiacnt when comparing mimics' voice and the nature voice of the mimic.

Aurally: The smaller signal-to-noise ratio within the recording and the more similar the context, the greater the percentage of accuracy in distinguishing bewteen speakers.

AURAL EXAMINATION:

Grand means: RIGHT WRONG UNDEC.

Grad. students 0.74 0.18 0.08

Professional 0.92 0.082 0.0

Examimers:

5 faculty

1 graduate student

Training duration:

"the authors were familiar with the ‘voiceprint' method of speaker identification"

Method:

visual ony (spectrograms were cut & mounted)

Speaker population:

25 faculty and graduate students of the University of Florida

Number of words:

7 words

Context type:

"I do not set the same store"

Temporal sequence:

contemporary

Type of trial:

open

Total number of trials:

25/examiner

Type of decision:

record a match/ indicate none was possible

Results:

". . . even skilled auditors such as these were unable to match correctly the disguised speech to the reference (normal) samples as much as 25% of the time . . . these groups were able to disguise their voices in such manners that their identification by the ‘voiceprint' technique became little more than a matter of chance."

Examimers:

2 PhD candidates in speech science

2 PhD candidates in speech pathology

Training duration:

3 courses in speech science plus previous experience with speech spectrograms: 4 weeks at 10-15 hr/wk

Method:

visual only (words excerpted and mounted)

Speaker population:

40 adult males (mean: 27.3 yrs)

Number of words:

9 words

Context type:

fixed context

Temporal sequence:

noncontemporary

Type of trial:

open

Total number of trials:

105 (7 matching tasks w/15 known & 15 unknown)

Type of decision:

1 to 5 certainty scale

Results:

The examiners were able to match speakers with a moderate degree of accuracy (55.67%) when there was no attemp to vocally disguise. Disguised speech significantly interfered with speaker identification. Further research is needed . . . in which the examiners may listen to the voice as well as view the spectrograms.

Examimers:

30 listeners

6 visual examiners

Training duration:

none

Method:

Study I: Aural

Study II: Visual (0 to 8kHz)

Speaker population:

12

Number of words:

four - 2 second speech segments

Context type:

random context

Temporal sequence:

contemporary/ noncontemporary (1wk)

Type of trial:

open

Total number of trials:

5 visual

38 aural

Type of decision:

same/different for each contemporary and noncontemporary

Results:

94% correct identifications were obtained for contemporary speech segments. 42% correct identifications were obtained for noncontemporary speech segments. 58.45% correct identifications were obtained when comparing different speakers. All examiners in pretest visual achieved 100% correct matching. Aural method is clearly superior to the spectrographic or ‘voiceprint' method

Examimers:

4 phoneticians

Training duration:

experienced

Method:

visual measurement of format fundamental frequency to obtain fo

Speaker population:

23 adult males

Number of words:

7 words ("I do not set the same store"

Context type:

fixed (normal & disguised) context

Temporal sequence:

contemporary

Type of trial:

Total number of trials:

46/phonetician

Type of decision:

Results:

A great amount of variablity in the fo was found between normal and disguised speech. The mean bandwidth differences (f1, f2, f3) for the group were large and also demonstrated considerable variability. Phonetic means also differed.

Examimers:

21 undergraduate students

Training duration:

series of lectures & discussions on phonetics, acoustics, and sound spectrography and speaker identification

Method:

visual only

Speaker population:

9 female, 5 male undergraduates - homogenous age and geographic background

Number of words:

9 words

Context type:

fixed context: 5 voice conditions (normal, lowered, falsetto, whispered and muffled)

Temporal sequence:

contemporary

Type of trial:

open

Total number of trials:

18 matches

Type of decision:

same/different

Results:

correct identifications:

F-voice M-voice

normal 100% 95%

lowered 85% 95%

falsetto 95% 90%

whispered 5% 98%

muffled 75% 100%

range: 39 to 70% correct

mean: 58.8%

Std.D.: 8.7%

Examimers:

7 students from Experimental phonetics

Training duration:

completion of Exp. I with feedback

Method:

visual only

Speaker population:

8 female, 8 male (mean age: 25.3 yrs)

Number of words:

8 words

Context type:

fixed context: "There's a bomb in the main post office"

Temporal sequence:

contemporary

Type of trial:

closed

Total number of trials:

16/examiner

Type of decision:

instructed to consider the sets in a particular order. All examiners considered undisguised before disguised

Results:

correct identifications:

F-voice M-voice

normal 71% 100%

lowered 85% 100%

falsetto 100% 67%

whispered 71% 71%

muffled 85% 100%

The results suggest that minimally trained examiners have little difficulty with spectrographic identification in closed, contemporary, undisguised trials. Results do not suggest that female voices are more difficult to identify than male voices.

Examimers:

professional and students

Training duration:

IAVA certified voice examiners and 2 weeks of training, respectively

Method:

aural only, visual only and aural/visual combined

Speaker population:

Chicano (25 female and 25 male)

Number of words:

four sentences approximately 2.4 seconds in Spanish

Context type:

fixed context

Temporal sequence:

noncontemporary

Type of trial:

open - randomized

Total number of trials:

600/examiner

Type of decision:

same, different, no opinion. qualified percentage of self-confidence from 51 to 100%

Results:

Student and Professional examiners for errors of elimination and identifcation had a mean percentile greater for noisy samples than for quiet samples, however, professional examiners srrors were due to aural only examinations whereas spectrographic/aural examinations produced 0.0% errors. The ‘no opinion' option was used more by professional examiners.

Examimers:

24 undergraduate students, 3 doctoral students, 3 professors of Speech and Hearing Science

Training duration:

brief lecture; 120 discrimination trials identical to the experiment

Method:

aural only

Speaker population:

40 adult males (mean age: 27.3 yrs)

Number of words:

9 words (it, is, on, you, and, the, I, to, me)

Context type:

fixed context

Temporal sequence:

noncontemporary (2 weeks +)

Type of trial:

open

Total number of trials:

18 matches

Type of decision:

same/different (1 to 5 certainty)

Results:

Both groups were ablt to discriminate speakers with moderately high degrees of accuracy, 92% correct for undisguised. Disguised trials ranged from 59 to 81% depending on the disguise. Recommended further research to studythe combined aural/spectrographic method.

Examimers:

3 professional, 5 trainees (less than 2 years experience)

Training duration:

professionals: 8 yrs each

trainees: < 2 yrs

Method:

aural only, visual only and aural/visual combined

Speaker population:

12 female, 12 male; American midwest dialect

Number of words:

24 words

Context type:

fixed context

Temporal sequence:

noncontemporary

Type of trial:

open

Total number of trials:

192 discrimination types

Type of decision:

the five IAVI alternatives

Results:

Professional examiners produced no errors of false identification or elimination. 1536 decisions by all eight examiners. Effect of restricted bandwidths (240-2K, 240-2.5K, 240-3K, and 240-4K) does not increase the errors but does increase the percentage of ‘no decisions'. Training of the examiner is very important on error rate. Trainees produced errors as follows: 6.1% false identifcation and 4.1% false elimination for all trials. However, at 240-4khz., 0.0% errors of false identification of elimination.

Examimers:

Federal Bureau of Investigation voice identification examiners

Training duration:

minimum of 2 yrs experience, completion of at least 100 actual voice comparision cases, formal approval by other trained examiners

Method:

combined aural/visual method

Speaker population:

actual criminal cases

Number of words:

vaired with each case

Context type:

Temporal sequence:

noncontemporary

Type of trial:

open

Total number of trials:

2000 forensic comparisons

Type of decision:

very similar

very dissimilar

no decision (low confidence)

Results:

number percent

no/low conf. 1304 65.2

elimination 378 18.9

identification 318 15.9

errors

false elim. 2 0.53

false id. 1 0.31