Bone conduction (BC) communication systems provide benefits over air conduction systems but are not in widespread use, partly due to problems with speech intelligibility. Contributing factors like device location and background noise have been explored, but little attention has been paid to the role of individual user differences. Because BC signals travel through an individual's skull and facial tissues, demographic factors such as user age, sex, race, or regional origin may influence sound transmission. Vocal traits such as pitch, spectral tilt, jitter, and shimmer may also play a role. Along with microphone placement and background noise, these factors can affect BC speech intelligibility. Eight diverse talkers were recorded with bone microphones on two different skull locations and in different background noise conditions. Twenty-four diverse listeners listened to these samples over BC and completed Modified Rhyme Tests for speech intelligibility. Forehead bone recordings were more intelligible than condyle recordings. In condyle recordings, female talkers, talkers with high fundamental frequency, and talkers in background noise were understood better, as were communications between talkers and listeners of the same regional origin. Listeners' individual traits had no significant effects. Thoughtful application of this knowledge can help improve BC communication for diverse users.

1.
Acker-Mills
,
B. E.
,
Houtsma
,
A. J. M.
, and
Ahroon
,
W. A.
(
2005
). “
Speech intelligibility with acoustic and contact microphones
,” in
New Directions for Improving Audio Effectiveness. Meeting Proceedings RTO-MP-HFM-123
(
Neuilly-sur-Seine
,
France, RTO
), pp.
1
14
.
2.
Acker-Mills
,
B. E.
,
Houtsma
,
A. J. M.
, and
Ahroon
,
W. A.
(
2006
). “
Speech intelligibility in noise using throat and acoustic microphones
,”
Aviat. Space Environ. Med.
77
,
26
31
.
3.
Akeroyd
,
M. A.
(
2008
). “
Are individual differences in speech reception related to individual differences in cognitive ability? A survey of twenty experimental studies with normal and hearing-impaired adults
,”
Int. J. Audiol.
47
,
S53
S71
.
4.
ANSI/ASA
(
2009
). ANSI/ASA S3.2-2009,
Method for Measuring the Intelligibility of Speech Over Communication Systems
, revision of ANSI S3.2-1989 (R 1999) (
American National Standards Institute/Acoustical Society of America
,
New York
).
5.
Bartlett
,
S. P.
,
Grossman
,
R.
, and
Whitaker
,
L. A.
(
1992
). “
Age-related changes of the craniofacial skeleton: An anthropometric and histologic analysis
,”
Plast. Reconstr. Surg.
90
,
592
600
.
6.
Benjamini
,
Y.
, and
Hochberg
,
Y.
(
1995
). “
Controlling the false discovery rate: A practical and powerful approach to multiple testing
,”
J. R. Statist. Soc. B.
57
,
289
300
.
7.
Boersma
,
P.
, and
Weenik
,
D.
(
2010
). “
Praat: Doing phonetics by computer [computer program]. Version 5.1.43
” (http://www.praat.org (Last viewed September 20, 2010).
8.
Bond
,
Z. S.
, and
Moore
,
T. J.
(
1994
). “
A note on the acoustic-phonetic characteristics of inadvertently clear speech
,”
Speech Commun.
14
,
325
337
.
9.
Bradlow
,
A. R.
,
Torretta
,
G. M.
, and
Pisoni
,
D. B.
(
1996
). “
Intelligibility of normal speech I: Global and fine-grained acoustic-phonetic talker characteristics
,”
Speech Commun.
20
,
255
272
.
10.
Burt
,
D. M.
, and
Perrett
,
D. I.
(
1995
). “
Perception of age in adult Caucasian male faces: Computer graphic manipulation of shape and colour information
,”
Proc. R. Soc. London, Ser. B
259
,
137
143
.
11.
Buss
,
E.
,
Hall
,
J. W. I.
, and
Grose
,
J. H.
(
2007
). “
Individual differences in the masking level difference with a narrowband masker at 500 or 2000 Hz
,”
J. Acoust. Soc. Am.
121
,
411
419
.
12.
Byrd
,
D.
(
1994
). “
Relations of sex and dialect to reduction
,”
Speech Commun.
15
,
39
54
.
13.
Castellanos
,
A.
,
Benedi
,
J. M.
, and
Casacuberta
,
F.
(
1996
). “
An analysis of general acoustic-phonetic features for Spanish speech produced with the Lombard effect
,”
Speech Commun.
20
,
23
35
.
14.
Clopper
,
C. G.
, and
Bradlow
,
A. R.
(
2008
). “
Perception of dialect variation in noise: Intelligibility and classification
,”
Lang. Speech
51
,
175
198
.
15.
De Coensel
,
B.
,
Botteldooren
,
D.
, and
De Muer
,
T.
(
2003
). “
1/f noise in rural and urban soundscapes
,”
Acta Acust. Acust.
89
,
287
295
.
16.
Enlow
,
D. H.
(
1966
). “
A morphogenetic analysis of facial growth
,”
Am. J. Orthod.
52
,
283
299
.
17.
Ferrario
,
V. F.
,
Sforza
,
C.
,
Pizzini
,
G.
,
Vogel
,
G.
, and
Miani
,
A.
(
1993
). “
Sexual dimorphism in the human face assessed by Euclidean distance matrix analysis
,”
J. Anat.
183
,
593
600
.
18.
Gripper
,
M.
,
McBride
,
M.
,
Osafo-Yeboah
,
B.
, and
Jiang
,
X.
(
2007
). “
Using the Callsign Acquisition Test (CAT) to compare the speech intelligibility of air versus bone conduction
,”
Int. J. Ind. Ergon.
37
,
631
641
.
19.
Hanson
,
H. M.
, and
Chuang
,
E. S.
(
1999
). “
Glottal characteristics of male speakers: Acoustic correlates and comparison with female data
,”
J. Acoust. Soc. Am.
106
,
1064
1077
.
20.
Hayes
,
D. P.
, and
Meltzer
,
L.
(
1967
). “
Bone-conducting microphones
,”
Am. J. Psychol.
80
,
619
624
.
21.
Henry
,
P.
, and
Letowski
,
T. R.
(
2007
).
Bone Conduction: Anatomy, Physiology, and Communication
(
Army Research Laboratory
,
Aberdeen Proving Ground, MD
), pp.
1
192
.
22.
Hodges
,
M. L.
, and
McBride
,
M. E.
(
2012
). “
Gender differences in bone conduction auditory signal processing: Communication equipment design implications
,”
Int. J. Ind. Ergon.
42
,
49
55
.
23.
Horwitz
,
A. R.
,
Ahlstrom
,
J. B.
, and
Dubno
,
J. R.
(
2012
). “
Individual and level-dependent differences in masking for adults with normal and impaired hearing
,”
J. Acoust. Soc. Am.
131
,
EL323
EL328
.
24.
Hudson
,
A. I.
, and
Holbrook
,
A.
(
1982
). “
Fundamental frequency characteristics of young black adults
,”
J. Speech Hear. Res.
25
,
25
28
.
25.
Hulett
,
D. M.
,
Bendick
,
M.
, Jr.
,
Thomas
,
S. Y.
, and
Mocco
,
F.
(
2008
). “
Enhancing women's inclusion in firefighting in the USA
,”
Int. J. Divers. Organ. Communities Nations
8
,
189
207
.
26.
Iseli
,
M.
,
Shue
,
Y. L.
, and
Alwan
,
A.
(
2007
). “
Age, sex, and vowel dependencies of acoustic measures related to the voice source
,”
J. Acoust. Soc. Am.
121
,
2283
2295
.
27.
Junqua
,
J. C.
(
1993
). “
The Lombard reflex and its role on human listeners and automatic speech recognizers
,”
J. Acoust. Soc. Am.
93
,
510
524
.
28.
Kasuya
,
H.
,
Yoshida
,
H.
,
Mori
,
H.
, and
Kido
,
H.
(
2008
). “
A longitudinal study on vocal aging—changes in F0, jitter, shimmer and glottal noise
,”
J. Acoust. Soc. Am.
123
,
3428
3438
.
29.
Keating
,
P. A.
,
Byrd
,
D.
,
Flemming
,
E.
, and
Todaka
,
Y.
(
1994
). “
Phonetic analyses of word and segment variation using the TIMIT corpus of American English
,”
Speech Commun.
14
,
131
142
.
30.
Kidd
,
G. R.
,
Watson
,
C. S.
, and
Gygi
,
B.
(
2007
). “
Individual differences in auditory abilities
,”
J. Acoust. Soc. Am.
122
,
418
435
.
31.
Kiliç
,
M. A.
, and
Ogüt
,
F.
(
2004
). “
The effect of the speaker gender on speech intelligibility in normal-hearing subjects with simulated high frequency hearing loss
,”
Rev. Laryngol. Otol. Rhinol.
125
,
35
38
.
32.
Labov
,
W.
, and
Ash
,
S.
(
1997
). “
Understanding Birmingham
,” in
Language Variety in the South Revisited
, edited by
C.
Bernstein
,
T.
Nunnally
, and
R.
Sabino
(
Alabama University Press
,
Tuscaloosa, AL
), pp.
508
573
.
33.
Labov
,
W.
,
Ash
,
S.
, and
Boberg
,
C.
(
1997
). “
A national map of the regional dialects of American English
,” in
TELSUR Project
(
Department of Linguistics, University of Pennsylvania
), http://www.ling.upenn.edu/phono_atlas/NationalMap/NatMap1.html (Last viewed August 24, 2011).
34.
Letowski
,
T.
,
Frank
,
T.
, and
Caravella
,
J.
(
1993
). “
Acoustical properties of speech produced in noise presented through supra-aural earphones
,”
Ear Hear.
14
,
332
338
.
35.
Letowski
,
T. R.
, and
Letowski
,
S. T.
(
2012
).
Auditory Spatial Perception: Auditory Localization
(
Army Research Laboratory
,
Aberdeen Proving Ground, MD
), pp.
1
152
.
36.
Lienard
,
J. S.
, and
Di Benedetto
,
M. G.
(
1999
). “
Effect of vocal effort on spectral properties of vowels
,”
J. Acoust. Soc. Am.
106
,
411
422
.
37.
Lu
,
Y.
, and
Cooke
,
M.
(
2008
). “
Speech production modifications produced by competing talkers, babble, and stationary noise
,”
J. Acoust. Soc. Am.
124
,
3261
3275
.
38.
Mason
,
H. M.
(
1946
). “
Understandability of speech in noise as affected by region or origin of speaker and listener
,”
Speech Monographs
13
,
54
58
.
39.
McBride
,
M.
,
Hodges
,
M.
, and
French
,
J.
(
2008a
). “
Speech intelligibility differences of male and female vocal signals transmitted through bone conduction in background noise: Implications for voice communication headset design
,”
Int. J. Ind. Ergon.
38
,
1038
1044
.
40.
McBride
,
M.
,
Letowski
,
T.
, and
Tran
,
P.
(
2008b
). “
Bone conduction reception: Head sensitivity mapping
,”
Ergonomics
51
,
702
718
.
41.
McBride
,
M.
,
Tran
,
P.
,
Letowski
,
T.
, and
Patrick
,
R.
(
2011
). “
The effect of bone conduction microphone locations on speech intelligibility and sound quality
,”
Appl. Ergon.
42
,
495
502
.
42.
Mendelson
,
B.
, and
Wong
,
C. H.
(
2012
). “
Changes in the facial skeleton with aging: Implications and clinical applications in facial rejuvenation
,”
Aesthetic Plast. Surg.
36
,
753
760
.
43.
Mendoza
,
E.
,
Valencia
,
N.
,
Munoz
,
J.
, and
Trujillo
,
H.
(
1996
). “
Differences in voice quality between men and women: Use of the long-term average spectrum (LTAS)
,”
J. Voice
10
,
59
66
.
44.
Nishio
,
M.
, and
Niimi
,
S.
(
2008
). “
Changes in speaking fundamental frequency characteristics with aging
,”
Folia Phoniatr. Logop.
60
,
120
127
.
45.
Nixon
,
C. W.
,
Morris
,
L. J.
,
McCavitt
,
A. R.
,
McKinley
,
R. L.
,
Anderson
,
T. R.
,
McDaniel
,
M. P.
, and
Yeager
,
D. G.
(
1998
). “
Female voice communications in high levels of aircraft cockpit noises—Part 1: Spectra, levels, and microphones
,”
Aviat. Space Environ. Med.
69
,
675
683
.
46.
Osafo-Yeboah
,
B.
,
Jiang
,
X.
,
McBride
,
M.
,
Mountjoy
,
D.
, and
Park
,
E.
(
2009
). “
Using the Callsign Acquisition Test (CAT) to investigate the impact of background noise, gender, and bone vibrator location on the intelligibility of bone-conducted speech
,”
Int. J. Ind. Ergon.
39
,
246
254
.
47.
Patten
,
E.
, and
Parker
,
K.
(
2011
). “
Women in the U.S. military: Growing share, distinctive profile
,” in
Pew Social and Demographic Trends
(
Pew Research Center
,
Washington, DC
), pp.
1
12
.
48.
Pittman
,
A. L.
, and
Wiley
,
T. L.
(
2001
). “
Recognition of speech produced in noise
,”
J. Speech. Lang. Hear. Res.
44
,
487
496
.
49.
Pollard
,
K. A.
,
Tran
,
P. K.
, and
Letowski
,
T. R.
(
2013
). “
A free-field method to calibrate bone conduction transducers
,”
J. Acoust. Soc. Am.
133
,
858
865
.
50.
Rose
,
E.
,
Kann
,
P.
, and
Jonas
,
I. E.
(
2001
). “
Speed of sound measurements in mandibular and phalangeal bone during growth
,”
Clin. Oral Investig.
5
,
2
5
.
51.
Russell
,
A.
, and
Penny
,
L.
(
1995
). “
Speaking fundamental frequency changes over time in women: A longitudinal study
,”
J. Speech Hear. Res.
38
,
101
109
.
52.
Simpson
,
A. P.
(
2009
). “
Phonetic differences between male and female speech
,”
Lang. Linguist. Compass
3
,
621
640
.
53.
Snidecor
,
J. C.
,
Rehman
,
I.
, and
Washburn
,
D. D.
(
1959
). “
Speech pickup by contact microphone at head and neck positions
,”
J. Speech Hear. Res.
2
,
277
281
.
54.
Stanley
,
R. M.
, and
Walker
,
B. N.
(
2009
). “
Intelligibility of bone-conducted speech at different locations compared to air-conducted speech
,” in
Proceedings of the Annual Meeting of the Human Factors and Ergonomics Society (HFES2009)
, October 19–23,
San Antonio, TX
, Vol.
53
, pp.
1086
1090
.
55.
Stevens
,
C.
,
Lees
,
N.
,
Vonwiller
,
J.
, and
Burnham
,
D.
(
2005
). “
On-line experimental methods to evaluate text-to-speech (TTS) synthesis: Effects of voice gender and signal quality on intelligibility, naturalness and preference
,”
Comput. Speech Lang.
19
,
129
146
.
56.
Stoicheff
,
M. L.
(
1981
). “
Speaking fundamental frequency characteristics of nonsmoking female adults
,”
J. Speech. Lang. Hear. Res.
24
,
437
441
.
57.
Studebaker
,
G. A.
(
1985
). “
A ‘rationalized’ arcsine transform
,”
J. Speech Hear. Res.
28
,
455
462
.
58.
Summers
,
W. V.
,
Pisoni
,
D. B.
,
Bernacki
,
R. H.
,
Pedlow
,
R. I.
, and
Stokes
,
M. A.
(
1988
). “
Effects of noise on speech production: Acoustic and perceptual analyses
,”
J. Acoust. Soc. Am.
84
,
917
928
.
59.
Surprenant
,
A. M.
, and
Watson
,
C. S.
(
2001
). “
Individual differences in the processing of speech and nonspeech sounds by normal-hearing listeners
,”
J. Acoust. Soc. Am.
110
,
2085
2095
.
60.
Tartter
,
V. C.
,
Gomes
,
H.
, and
Litwin
,
E.
(
1993
). “
Some acoustic effects of listening to noise on speech production
,”
J. Acoust. Soc. Am.
94
,
2437
2440
.
61.
Theodore
,
R. M.
,
Miller
,
J. L.
, and
DeSteno
,
D.
(
2009
). “
Individual talker differences in voice-onset-time: Contextual influences
,”
J. Acoust. Soc. Am.
125
,
3974
3982
.
62.
Toll
,
L. E.
,
Emanuel
,
D. C.
, and
Letowski
,
T.
(
2011
). “
Effect of static force on bone conduction hearing thresholds and comfort
,”
Int. J. Audiol.
50
,
632
635
.
63.
Tran
,
P.
,
Letowski
,
T.
, and
McBride
,
M.
(
2008
). “
Bone conduction microphone: Head sensitivity mapping for speech intelligibility and sound quality
,” in
International Conference on Audio, Language and Image Processing (ICALIP 2008)
,
Shanghai, China
, pp.
107
111
.
64.
Tran
,
P. K.
,
Letowski
,
T. R.
, and
McBride
,
M. E.
(
2013
). “
The effect of bone conduction microphone placement on intensity and spectrum of transmitted speech items
,”
J. Acoust. Soc. Am.
133
,
3900
3908
.
65.
Whiteside
,
S. P.
(
2001
). “
Sex-specific fundamental and formant frequency patterns in a cross-sectional study
,”
J. Acoust. Soc. Am.
110
,
464
478
.
66.
Wilcox
,
K. A.
, and
Horii
,
Y.
(
1980
). “
Age and changes in vocal jitter
,”
J. Gerontol.
35
,
194
198
.
67.
Yao
,
W. J.
,
Wu
,
C. H.
,
Wang
,
S. T.
,
Chang
,
C. J.
,
Chiu
,
N. T.
, and
Yu
,
C. Y.
(
2001
). “
Differential changes in regional bone mineral density in healthy Chinese: Age-related and sex-dependent
,”
Calcif. Tissue Int.
68
,
330
336
.
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