Friday 4 July 2008 – SC00/4 – Speech Communication IV
5aSCc : ACOUSTICS2008/1165

The effect of learning onlistening to ultra-fast speech
T. Nishimoto (The Univ. of Tokyo)
Y. Kariya and T. Watanabe(Tokyo Woman’s Christian Univ.)
1

Objective• Visually impaired persons– use PC with voice-enabling software– get information via synthesized voice– important to acquire information efficiently– Ultra-fast speech : they can practice• This work : observe the learning effect– effect of word familiarity– intelligibility & mental workload• undesirable when mental workload increases2

Prior work
• [Asakawa et. al. 2003, 2005]– fast speech by shortening the recorded human voices– by the skilled users of the screen reading software– The skilled listeners assessed• the appropriate speed as 19.5 morae/sec (recall 90%)
• the ultimate speed as 25.0 morae/sec (recall 50%)

• [Nishimoto et. al. 2006, 2007]– TTS voices : 4-digit numbers (18-30 morae/sec)– experiments with young persons• significant learning effects• sustained for several weeks– age-related effects : intercept the learning• difficulty of recall digits in the correct order3

Listening ultra-fast speech• Bottom-up process– dominant when low-familiarity task
– learning effect : less significant– mental workload : highstimuli• Top-down process– lexicon is important– mental workload : lowlearning / knowledge

perception

speaker / voicerecognition

mental lexicon

short-term memory
long-term memory• Word familiarity

answer– awareness influences the learning effect4

Estimation of mental workload• NASA-TLX : weighted mean workload– Mental demand / Physical demand– Temporal pressure / Effort– Frustration level / Performance

WWL score• easy to use, reliably sensitive
explanation

ranking

evaluation
listeningultra-fastspeechmagnitude
magnitude ofof factor
factor (6-1)(6-1)

valuesvalues ofof 0-100
0-100
forfor 66 factors
factors

rest time (5min) before next task5Preliminary experiment• Results : significance in WWL & intelligibility– except the case between FH-S2 and FL-S1• speed : S1=original / S2=2.0 times faster• familiarity : FH / FLIntelligibility

Intelligibility

WWL
WWL andand intelligibility
intelligibility score
score ofof each
each subject
subject (N=10)(N=10)

10080

6040
FH-S1

FH-S2

FL-S1

FL-S2

Weighted Workload

WWL80

N-WWL

706050Normalization of WWL

40

Transformed the ave. and SD of WWLof each subject to 50 and 10, respectively

30
20
FH-S1

FH-S2

FL-S1

FL-S2

6

Familiarity controlled speech• FW03 [Amano2006]– audio data set for word intelligibility test• based on Japanese word familiarity database– 4 levels of familiarity• 4 morae words : accent controlled• a group consists of 50 words : phoneme balanced– Recorded speech• speed controlled, loudness level calibrated• Stimuli : audio speed conversion was used
– 4 times faster = approx. 20 morae / sec– highest (H) / lowest (L) familiarity groups were used

• Evaluation : number of correct morae
7Experiment• Subjects (N=59) : divided into 4 groups– PC with headphones for everyone– Input roman characters with key-board• Each trial consists of 50 words– 16 seconds interval– word familiarity was not informed
S1,S1, S2,S2, S3
S3 :: different
different vocabulary
vocabulary (same(same condition)condition)Group

Trial 1

Trial 2

Trial 3

G1 : L-L-L

FLS1

FLS2

FLS3

difficult to use mental lexicon

G2 : H-H-L FHS1

FHS2

FLS3

G3 : L-L-H

FLS1

FLS2

FHS3

if they are not aware of the change,
they do not use mental lexicon

G4 : H-H-H FHS1

FHS2

FHS3

if they are aware of high familiarity,
they can use mental lexicon

8

G1 : L-L-L (N=16)

G3 : L-L-H (N=14)

peak of learning effect at T2

not significant WWL reduction at T3

Intelligibility
Intelligibility
T1-T2,
T1-T2, T1-T3
T1-T3 :: ****G2 : H-H-L (N=15)Intelligibility
Intelligibility && WWL
WWL
T2-T3,
T2-T3, T1-T3
T1-T3 :: ****Intelligibility
Intelligibility
T1-T2,
T1-T2, T2-T3,
T2-T3, T1-T3
T1-T3 :: ****WWL
WWL T2-T3
T2-T3 :: ****** :: pp << 0.050.05** :: 0.05
0.05 << pp << 0.100.10(t-test(t-test ofof two
two tailed
taileddistributions)distributions)G4 : H-H-H (N=14)Intelligibility
Intelligibility
T2-T3,T2-T3, T1-T3
T1-T3 :: **
**WWL
WWL
T1-T2
T1-T2 :: **T2-T3,
T2-T3, T1-T3
T1-T3 :: ****NoNo significant
significant
differences
differences
betweenbetweenT3
T3 ofof G1-G2
G1-G2
andandT3
T3 ofof G3-G4,
G3-G4,
respectively
respectively

significant WWL
reduction at T39Conclusion• Learning reduces mental workload
if lexicon is used
L-L-H• Without using lexicon,with indication of familiarity (N=7)
learning effect is limited• Awareness is the key– indications may change• Future work:– longer period experiment– age-related effects– TTS applications

Intelligibility
Intelligibility
T1-T2,
T1-T2, T2-T3,
T2-T3, T1-T3
T1-T3 :: ****WWL
WWL T2-T3,
T2-T3, T1-T3
T1-T3 :: ****Acknowledgment:
Acknowledgment: A.
A. SegawaSegawa (TWCU)(TWCU) performed
performed additional
additional experiment.
experiment.

10