The measurement and analysis of underwater sound is a complicated process because of the variable durations of contributing sources and constantly changing water column dynamics. Because the ambient sound distribution does not always follow a Gaussian structure and may be nonstationary in time, analysis over an extended period is required to accurately characterize the data. Utilizing recordings from the Indian Ocean, the temporal variation in ambient sound including transient signals was examined using multiple processing window lengths and subsampling intervals. Results illustrate the degree of uncertainty in sound levels based on different units of analysis. The average difference between sound level estimates in the 10–30 Hz band due to subsampling was 2 dB and as high as 4 dB. The difference in the full band (5–110 Hz) was as high as 6 dB. Longer averaging windows (200 vs 60 s) resulted in larger variations over different subsampling intervals. This work demonstrates how sampling protocols within a single dataset can influence results and acknowledges that comparative studies at the same location but with different sampling protocols can be substantial if signal processing parameters are not statistically accounted for to confirm interpretation of results and observed trends.

1.
Andrew
,
R. K.
,
Howe
,
B. M.
,
Mercer
,
J. A.
, and
Dzieciuch
,
M. A.
(
2002
). “
Ocean ambient sound: Comparing the 1960s with the 1990s for a receiver off the California coast
,”
Acoust. Res. Lett. Online
3
(
2
),
65
70
.
2.
Au
,
W. W. L.
, and
Hastings
,
M. C.
(
2008
).
Principles of Marine Bioacoustics
(
Springer Science
,
New York
), Chap. 10, pp.
401
490
.
3.
Bendat
,
J. S.
, and
Piersol
,
A. G.
(
2000
).
Random Data Analysis and Measurement Procedures. Series in Probability and Statistics
(
Wiley
,
New York
), Chap. 12, pp.
457
517
.
4.
Blackman
,
D. K.
,
Groot-Hedlin
,
C.
,
Harben
,
P.
,
Sauter
,
A.
, and
Orcutt
,
J. A.
(
2004
). “
Testing low/very low frequency acoustic sources for basin-wide propagation in the Indian Ocean
,”
J. Acoust. Soc. Am.
116
(
4
),
2057
2066
.
5.
Cato
,
D. H.
(
1976
). “
Ambient sea noise in waters near Australia
,”
J. Acoust. Soc. Am.
60
(
2
),
320
328
.
6.
Chapman
,
N. R.
, and
Price
,
A.
(
2011
). “
Low frequency deep ocean ambient noise trends in the Northeast Pacific Ocean
,”
J. Acoust. Soc. Am.
129
(
5
),
EL161
EL165
.
7.
Chapp
,
E.
,
Bohnenstiehl
,
D. R.
, and
Tolstoy
,
M.
(
2005
). “
Sound-channel observations of ice-generated tremor in the Indian Ocean
,”
Geochem. Geophys. Geosyst.
6
,
Q06003
, doi:.
8.
CTBTO Preparatory Commission
. (
2008
). “
HA08: British Indian Ocean Territory (BIOT) Chagos Archipelago, United Kingdom
,” retrieved from http://www.ctbto.org (Last viewed 7/2/2013).
9.
Curtis
,
K. R.
,
Howe
,
B. M.
, and
Mercer
,
J. A.
(
1999
). “
Low-frequency ambient sound in the North Pacific: Long time series observations
,”
J. Acoust. Soc. Am.
106
(
6
),
3189
3200
.
11.
Gavrilov
,
A.
, and
Li
,
B.
(
2008
). “
Long-term variations of ice breaking noise in Antarctica
,”
J. Acoust. Soc. Am.
123
,
2989
2990
.
12.
Glass
,
G. V.
,
Peckham
,
P. D.
, and
Sanders
,
J. R.
(
1972
). “
Consequences of failure to meet assumptions underlying fixed effects analyses of variance and covariance
,”
Rev. Educ. Res.
42
(
3
),
238
288
.
13.
Hanson
,
J. A.
(
2001
). “
Initial analysis of data from the new Diego Garcia hydroacoustic station
,”
Seismic Res. Rev.: Worldwide Monitor. Nuclear Expl.
23
,
12
22
.
14.
Hanson
,
J. A.
, and
Bowman
,
J. R.
(
2006
). “
Methods for monitoring hydroacoustic events using direct and reflected T waves in the Indian Ocean
,”
J. Geophys. Res.
111
:
B02305
. Doi 10.1029/2004JB003609.
16.
Klinck
,
H.
,
Nieukirk
,
S. L.
,
Mellinger
,
D. K.
,
Klinck
,
K.
,
Matsumoto
,
H.
, and
Dziak
,
R. P.
(
2012
). “
Seasonal presence of cetaceans and ambient noise levels in polar waters of the North Atlantic
,”
J. Acoust. Soc. Am.
132
(
3
),
EL176
181
.
17.
Lawrence
,
M. W.
(
2004
). “
Acoustic monitoring of the global ocean for the CTBT
,” in
Proceedings of ACOUSTICS 1
, pp.
455
460
.
18.
Lix
,
L. M.
,
Keselman
,
J. C.
, and
Keselman
,
H. J.
(
1996
). “
Consequences of assumption violations revisited: A quantitative review of alternatives to the one-way analysis of variance F test
,”
Rev. Educ. Res.
66
,
579
619
.
18.
McDonald
,
M. A.
,
Hildebrand
,
J. A.
, and
Wiggins
,
S. M.
(
2006
). “
Increases in deep ocean ambient noise west of San Nicolas Island, California
,”
J. Acoust. Soc. Am.
120
(
2
),
711
717
.
19.
McDonald
,
M. A.
,
Hildebrand
,
J. A.
,
Wiggins
,
S. M.
, and
Ross
,
D. A.
(
2008
). “
50 year comparison of ambient ocean noise near San Clemente Island: A bathymetrically complex coastal region off Southern California
,”
J. Acoust. Soc. Am.
124
(
4
),
1985
1992
.
20.
McKenna
,
M. F.
,
Ross
,
D.
,
Wiggins
,
S. M.
, and
Hildebrand
,
J. A.
(
2012
). “
Underwater radiated noise from modern commercial ships
,”
J. Acoust. Soc. Am.
131
(
1
),
92
103
.
21.
Medwin
,
H.
(
2005
).
Sounds in the Sea: From Ocean Acoustics to Acoustical Oceanography
(
Cambridge University Press
,
New York
), Chap. 1, pp.
7
49
.
22.
Merchant
,
N. D.
,
Blondel
,
P.
,
Dakin
,
D. T.
, and
Dorocicz
,
J.
(
2012
). “
Averaging underwater noise levels for environmental assessment of shipping
,”
J. Acoust. Soc. Am.
132
(
4
),
343
349
.
22.
Miksis-Olds
,
J. L.
,
Bradley
,
D. L.
, and
Niu
,
X. M.
(
2013
). “
Decadal trends in Indian Ocean ambient sound
,”
J. Acoust. Soc. Am.
134
,
3464
3475
.
23.
National Research Council
(
2003
).
Marine Mammals and Low-Frequency Sound: Progress Since 1994
(
National Academy Press
,
Washington, DC
), p.
146
.
25.
Prior
,
M. K.
,
Brown
,
D. J.
, and
Haralabus
,
G.
(
2011
). “
Data features from long-term monitoring of ocean noise
,” in
Proceedings of the 4th International Conference and Exhibition on Underwater Acoustic Measurements: Technologies and Results
,
Kos
,
Greece
, edited by
J. S.
Papadakis
and
L.
Bjønø
, p.
8
.
28.
Ross
,
D.
(
1993
). “
On ocean underwater ambient noise
,”
Acoust. Bull.
18
,
5
8
.
29.
Roth
,
E. H.
,
Hildebrand
,
J. A.
,
Wiggins
,
S. M.
, and
Ross
,
D.
(
2012
). “
Underwater ambient noise on the Chukchi Sea continental slope from 2006–2009
,”
J. Acoust. Soc. Am.
131
(
1
),
104
110
.
30.
Samaran
,
F.
,
Adam
,
O.
, and
Guinet
,
C.
(
2010
). “
Detection range modeling of blue whale calls in the Southern Indian Ocean
,”
Appl. Acoust.
71
,
1099
1106
.
31.
Sirovic
,
A.
,
Hildebrand
,
J. A.
, and
Wiggins
,
S. M.
(
2009
). “
Blue and fin whale acoustic presence around Antarctica during 2003 and 2004
,”
Mar. Mamm. Sci.
25
(
1
),
125
136
.
32.
Tolstoy
,
M.
, and
Bohnenstiehl
,
D. R.
(
2002
). “
Analysis of hydroacoustic signals in the Indian Ocean
,” in
24th Seismic Research Review
, Ponte Vedra Beach, Florida, September 17–19. Available from http://www.rdss.info/librarybox/mrr/srr2002/screen/04-05.pdf (Last viewed 7/2/2013).
33.
Wagstaff
,
R. A.
, and
Aitkenhead
,
J. W.
(
2005
). “
Ambient noise measurements in the Northwest Indian Ocean
,”
IEEE J. Ocean. Eng.
30
(
2
),
295
302
.
35.
Wenz
,
G. M.
(
1962
). “
Acoustic ambient noise in the ocean: Spectra and sources
,”
J. Acoust. Soc. Am.
34
,
1936
1956
.
36.
Wenz
,
G. M.
(
1964
). “
Ambient noise measurements west of San Clemente Island
,” U.S. Navy Electronics Laboratory Report No. 1235, declassified 1970, p.
46
.
37.
Wenz
,
G. M.
(
1969
). “
Low-frequency deep-water ambient noise along the Pacific Coast of the United States
,”
U.S. Navy J. Underwater Acoustics
, Vol.
19
, pp.
423
444
, declassified 1997.
38.
Wenz
,
G. M.
,
Calderon
,
M. A.
, and
Scanlan
,
T. F.
(
1965
). “
Underwater acoustic ambient-noise and transmission tests west of San Clemente Island, July 1963
,” U.S. Navy Electronics Laboratory Report No. 1260, declassified 1994. p.
46
.
You do not currently have access to this content.