Vowel formant discrimination in highfidelity speech by hearing-impaired
listeners.
Diane Kewley-Port,
Chang Liu (also University at Buffalo,)
T. Zachary Burkle
Indiana University, SPHS
Presented at the Acoustical Society of America Meeting,
Austin, TX, Nov. 11, 2003.
Thanks to SPL Lab members
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Larry Humes (Investigator)
Maureen Coughlin (Audiologist, ABD)
Kelley Anderson (Research Assistant)
Bill Mills (Programmer)
Formant Discrimination
• Just noticeable difference between standard
vowel and one with shifted formant.
• Psychophysical procedures to determine
thresholds formant frequency, DF (Hz).
• For 10+ years, experiments have
systematically varied conditions, phonetic
context, F0, noise etc.
• Purpose: Examine formant thresholds for
hearing-impaired listeners (HI) in nearly
natural speech, including sentences
High-Fidelity Speech
• To preserve naturalness, use STRAIGHT
(Kawahara et al., 1999) synthesis
• Stimulus Samples for word “bad”
– Sentence
– Word (standard vowel)
– Word (10% F1 increment,
NH, optimal listening
Weber Fraction = 1.5%)
Formant Thresholds Hi-Fi NH
Delta F (Hz)
150.0
ISO Hi-Fi
125.0
Word Hi-Fi
100.0
Sent Hi-Fi
190%
160%
75.0
50.0
25.0
0.0
ih1
eh1
uh1
ae1
uh2
Vowel formant
eh2
ae2
ih2
Experimental Factors for HI study
• Formant Frequency: / I E Q Ã / F1 & F2
• Audibility: 70 dB SPL partial vs.
95 dB SPL fully
• Linguistic Context: isolated vowels, words,
sentences
• Sent + ID task:
Sentence discrimination only vs.
Sentence discrimination + ID
Hearing Impaired Listeners
• 21 – 55 years old, N = 5
• Mild – moderate, high-frequency loss
Procedures
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•
•
•
Day 1
Screening
Days 2-4 Training
Days 5-23 Testing
Linguistic Context (ISO, Word, Sent) and
Sent + ID blocks randomized daily
• 95 vs. 70 dB SPL levels fixed each day
Summary Threshold Results
Factor
Significant
• Formant Frequency (8)
Yes
• Audibility (70 vs 95)
No
• Linguistic Context
(ISO, Word, Sent)
Yes
• Sent + ID task
No
• Explain with figures
Isolated Vowels Hi-fi
300.0
ISO HI 70
ISO HI 95
Delta F (Hz)
1) Formant
Frequency
ISO NH 70
250.0
200.0
150.0
100.0
2)Audibility
50.0
0.0
ih1
eh1
uh1
ae1
uh2
eh2
ae2
ih2
Vowel formant
Sentences Hi-fi
300.0
Sent 95
250.0
Delta F (Hz)
Sent 70
200.0
150.0
100.0
50.0
0.0
ih1
eh1
uh1
ae1
uh2
Vowel formant
eh2
ae2
ih2
3) Linguistic Context. Thresholds different
• Post-hocs, only DF word < DF Sent
• Why?
Linguistic Context Hi-Fi HI
300
ISO
250
Word
Sent
Delta F (Hz)
200
150
100
50
0
ih1
eh1
uh1
ae1
uh2
Vowel formant
eh2
ae2
ih2
Reversal, DF Iso > DF Word
Linguistic Context 95 dB Hi-Fi HI
300
ISO
Delta F (Hz)
250
Word
200
150
100
50
0
ih1
eh1
uh1
ae1
uh2
Vowel formant
eh2
ae2
ih2
Comparison HI to NH (Hi-Fi)
HI vs. NH 70 dB SPL Hi-Fi
300
250
Word NH
Word HI
Delta F (Hz)
200
Sent NH
150
Sent HI
100
50
0
ih1
eh1
uh1
ae1
uh2
Vowel formant
eh2
ae2
ih2
Thresholds Hi-Fi vs. Synthetic Speech
• Richie, Kewley-Port, & Coughlin (2003)
reported DF for isolated formant
synthesized vowels (Syn) for HI
• Liu & Kewley-Port (2003) report for NH
no difference Hi-Fi and Syn for isolated
vowels and words
• Predict that thresholds for our Hi-Fi
vowels same as Syn vowels from Richie et al.
•Hi-Fi elevated by 150%
Hi-Fi vs. Syn Isolated Vowels Soft
300.0
Hi-Fi NH
Delta F (Hz)
250.0
Syn HI
Hi-Fi HI
200.0
150.0
100.0
50.0
0.0
ih1
eh1
uh1
ae1
uh2
Vowel formant
eh2
ae2
ih2
Summary
• Formant discrimination by HI significantly
effected by
– Formant Frequency
– Linguistic Context
– Speech quality (Hi-Fi harder)
• Surprising Hi-Fi threshold comparisons
– Thresholds for softer sentences better than
louder
– Thresholds for words better than isolated
vowels
Baseline Thresholds
Normal Hearing Listeners (NH)
Formant Synthesized (Syn)
Female Isolated (ISO) Vowels F1 & F2
Four Vowels: / I E Q Ã /
Formant Thresholds Syn NH
100
90
80
Delta F (Hz)
•
•
•
•
70
60
50
40
30
20
10
0
ih1
eh1
uh1
ae1
uh2
Vowel formant
ISO
ae2
eh2
ih2
Linguistic Context Syn
Formant Thresholds Syn NH
100
90
250%
80
Delta F (Hz)
70
170%
60
50
40
30
20
10
0
ih1
eh1
uh1
ae1
uh2
Vowel
Sent formant
ISO
22 C VC
ae2
eh2
ih2
Added ID Task
Thresholds with or without ID Task
Hi-Fi HI
300
250
Threshold (Hz)
200
95
95
70
70
150
100
50
0
0
500
1000
1500
Formant fre que ncy (Hz)
2000
2500
dB,
dB,
dB,
dB,
Sen.
sen+ID
sen
sen+ID
Audibility versus Pathology
• Vowels fully audible 70 dB NH, 95 dB HI
DF2 elevated by 200 %
Fully Audible
HI vs. NH Word Hi-Fi
300
250
NH 70
Delta F (Hz)
200
HI 95
150
100
50
0
ih1
eh1
uh1
ae1
uh2
Vowel formant
eh2
ae2
ih2
Liste n e r V ariab ility at 70 d B fo r W o rd
400.0
300.0
D elta F (H z)
B AC
BC C
200.0
C LM
D LN
JR M
100.0
0.0
ih1
eh1
uh1
ae1
uh2
V ow elFrom ant
eh2
ae2
ih2