Loudness level measurements in human listeners are straightforward; however, it is difficult to convey the concepts of loudness matching or loudness comparison to (non-human) animals. For this reason, prior studies have relied upon objective measurements, such as response latency, to estimate equal loudness contours in animals. In this study, a bottlenose dolphin was trained to perform a loudness comparison test, where the listener indicates which of two sequential tones is louder. To enable reward of the dolphin, most trials featured tones with identical or similar frequencies, but relatively large sound pressure level differences, so that the loudness relationship was known. A relatively small percentage of trials were “probe” trials, with tone pairs whose loudness relationship was not known. Responses to the probe trials were used to construct psychometric functions describing the loudness relationship between a tone at a particular frequency and sound pressure level and that of a reference tone at 10 kHz with a sound pressure level of 90, 105, or 115 dB re 1 μPa. The loudness relationships were then used to construct equal loudness contours and auditory weighting functions that can be used to predict the frequency-dependent effects of noise on odontocetes.

1.
ANSI
(
2006
). S1.42-2001 (R 2006),
American National Standard Design Response of Weighting Networks for Acoustical Measurements
(
Acoustical Society of America
,
New York
).
2.
Finneran
,
J. J.
(
2010
). “
Auditory effects of underwater noise in odontocetes
,” in Second International Conference on the Effects of Noise on Aquatic Life, Cork, Ireland.
3.
Finneran
,
J. J.
,
Carder
,
D. A.
,
Schlundt
,
C. E.
, and
Dear
,
R. L.
(
2010
). “
Growth and recovery of temporary threshold shift (TTS) at 3 kHz in bottlenose dolphins (Tursiops truncatus)
,”
J. Acoust. Soc. Am.
127
,
3256
3266
.
4.
Finneran
,
J. J.
, and
Schlundt
,
C. E.
(
2007
). “
Underwater sound pressure variation and bottlenose dolphin (Tursiops truncatus) hearing thresholds in a small pool
,”
J. Acoust. Soc. Am.
122
,
606
614
.
5.
Finneran
,
J. J.
, and
Schlundt
,
C. E.
(
2010
). “
Frequency-dependent and longitudinal changes in noise-induced hearing loss in a bottlenose dolphin (Tursiops truncatus)
,”
J. Acoust. Soc. Am.
128
,
567
570
.
6.
Fletcher
,
H.
, and
Munson
,
W. A.
(
1933
). “
Loudness, its definition, measurement and calculation
,”
J. Acoust. Soc. Am.
5
,
82
108
.
7.
Gellerman
,
L. W.
(
1933
). “
Chance orders of alternating stimuli in visual discrimination experiments
,”
J. Genet. Psychol.
42
,
206
208
.
8.
Johnson
,
C. S.
(
1968
). “
Relation between absolute threshold and duration-of-tone pulses in the bottlenosed porpoise
,”
J. Acoust. Soc. Am.
43
,
757
763
.
9.
Kastelein
,
R. A.
,
Wensveen
,
P. J.
,
Terhune
,
J. M.
, and
Jong
,
C. A. F. D.
(
2011
). “
Near-threshold equal-loudness contours for harbor seals (Phoca vitulina) derived from reaction times during underwater audiometry: A preliminary study
,”
J. Acoust. Soc. Am.
129
,
488
495
.
10.
Møller
,
H.
, and
Andresen
,
J.
(
1984
). “
Loudness of pure tones at low and infrasonic frequencies
,”
Low Freq. Noise, Vib., Act. Control
3
,
78
87
.
11.
Nedwell
,
J. R.
,
Turnpenny
,
A. W. H.
,
Lovell
,
J.
,
Parvin
,
S. J.
,
Workman
,
R.
,
Spinks
,
J. A. L.
, and
Howell
,
D.
(
2007
). “
A validation of the dBht as a measure of the behavioural and auditory effects of underwater noise
,” 534R1231 (Subacoustech Acoustic Research Consultancy, Southampton, Hampshire, UK).
12.
Origin
(
2007
). Version 8 (OriginLab Corporation, Northampton, MA).
13.
Pfingst
,
B. E.
,
Hienz
,
R.
,
Kimm
,
J.
, and
Miller
,
J.
(
1975
). “
Reaction-time procedure for measurement of hearing. I. Suprathreshold functions
,”
J. Acoust. Soc. Am.
57
,
421
430
.
19.
Ridgway
,
S. H.
,
Carder
,
D. A.
,
Kamolnick
,
P. L.
,
Skaar
,
D. J.
, and
Root
,
W. A.
(
1991
). “
Acoustic response times (RTs) for Tursiops truncatus
,”
J. Acoust. Soc. Am.
89
,
1967
1968
.
20.
Ridgway
,
S.
, and
Carder
,
D.
(
2000
). “
A preliminary study of loudness at frequencies of 5 to 120 kHz based on whistle response time (RT) in a dolphin
,”
J. Acoust. Soc. Am.
108
,
2515
A
.
14.
Robinson
,
D. W.
, and
Dadson
,
R. S.
(
1956
). “
A re-determination of the equal-loudness relations for pure tones
,”
Br. J. Appl. Phys.
7
,
166
181
.
15.
Schlundt
,
C. E.
,
Finneran
,
J. J.
,
Carder
,
D. A.
, and
Ridgway
,
S. H.
(
2000
). “
Temporary shift in masked hearing thresholds of bottlenose dolphins, Tursiops truncatus, and white whales, Delphinapterus leucas, after exposure to intense tones
,”
J. Acoust. Soc. Am.
107
,
3496
3508
.
16.
Southall
,
B. L.
,
Bowles
,
A. E.
,
Ellison
,
W. T.
,
Finneran
,
J. J.
,
Gentry
,
R. L.
,
Greene
,
C. R.
, Jr.
,
Kastak
,
D.
,
Ketten
,
D. R.
,
Miller
,
J. H.
,
Nachtigall
,
P. E.
,
Richardson
,
W. J.
,
Thomas
,
J. A.
, and
Tyack
,
P. L.
(
2007
). “
Marine mammal noise exposure criteria: Initial scientific recommendations
,”
Aquat. Mamm.
33
,
411
521
.
17.
Stebbins
,
W. C.
(
1966
). “
Auditory reaction time and the derivation of equal loudness contours for the monkey
,”
J. Exp. Anal. Behav.
9
,
135
142
.
18.
Suzuki
,
Y.
, and
Takeshima
,
H.
(
2004
). “
Equal-loudness-level contours for pure tones
,”
J. Acoust. Soc. Am.
116
,
918
933
.
You do not currently have access to this content.