Marine Sanctuaries Conservation Series MSD-05-1 

U.S. Department of Commerce February 2005 

National Oceanic and Atmospheric Administration 

National Ocean Service 

Office of Ocean and Coastal Resource Management 

Marine Sanctuaries Division 

Noise Levels and Sources in the Stellwagen Bank National 

Marine Sanctuary and the St. Lawrence River Estuary 
About the Marine Sanctuaries Conservation Series 

The National Oceanic and Atmospheric Administration’s Marine Sanctuary Division (MSD) 

administers the National Marine Sanctuary Program. Its mission is to identify, designate, 

protect and manage the ecological, recreational, research, educational, historical, and aesthetic 

resources and qualities of nationally significant coastal and marine areas. The existing marine 

sanctuaries differ widely in their natural and historical resources and include nearshore and 

open ocean areas ranging in size from less than one to over 5,000 square miles. Protected 

habitats include rocky coasts, kelp forests, coral reefs, sea grass beds, estuarine habitats, hard 

and soft bottom habitats, segments of whale migration routes, and shipwrecks. 

Because of considerable differences in settings, resources, and threats, each marine sanctuary 

has a tailored management plan. Conservation, education, research, monitoring and 

enforcement programs vary accordingly. The integration of these programs is fundamental to 

marine protected area management. The Marine Sanctuaries Conservation Series reflects and 

supports this integration by providing a forum for publication and discussion of the complex 

issues currently facing the National Marine Sanctuary Program. Topics of published reports 

vary substantially and may include descriptions of educational programs, discussions on 

resource management issues, and results of scientific research and monitoring projects. The 

series facilitates integration of natural sciences, socioeconomic and cultural sciences, 

education, and policy development to accomplish the diverse needs of NOAA’s resource 

protection mandate. 
Noise Levels and Sources in the Stellwagen Bank National 

Marine Sanctuary and the St. Lawrence River Estuary 

Peter M. Scheifele and Michael Darre 

National Undersea Research Center, North Atlantic and Great Lakes, and Animal Sciences 

Department, University of Connecticut 

 

Silver Spring, Maryland 

February 2005 

U.S. Department of Commerce 

Carlos M. Gutierrez, Secretary 

National Oceanic and Atmospheric Administration 

VADM Conrad C. Lautenbacher, Jr. (USN-ret.) 

Under Secretary of Commerce for Oceans and Atmosphere 

National Ocean Service 

Richard W. Spinrad, Ph.D., Assistant Administrator 

Marine Sanctuaries Division 

Daniel J. Basta, Director 
DISCLAIMER 

Report content does not necessarily reflect the views and policies of the National Marine 

Sanctuary Program or the National Oceanic and Atmospheric Administration, nor does the 

mention of trade names or commercial products constitute endorsement or recommendation for 

use. 

REPORT AVAILABILITY 

Electronic copies of this report may be downloaded from the National Marine Sanctuaries 

Program web site at www.sanctuaries.nos.noaa.gov. Hard copies may be available from the 

following address: 

 National Oceanic and Atmospheric Administration

 Marine Sanctuaries Division

 SSMC4, N/ORM62 

 1305 East-West Highway 

 Silver Spring, MD 20910 

COVER 

Original Photo: Joseph Mobely, NMFS Permit #810 

Photo Effects and Design: Spencer Connaughton 

SUGGESTED CITATION

Scheifele, Peter M. and Michael Darre. 2005. Noise levels and sources in the Stellwagen Bank 

National Marine Sanctuary and the St. Lawrence River Estuary. Marine Conservation Series 

MSD-05-1. U. S. Department of Commerce, National Oceanic and Atmospheric Administration, 

Marine Sanctuaries Division, Silver Spring, MD. 26pp. 

CONTACT 

National Undersea Research Center, North Atlantic and Great Lakes, and Animal Sciences 

Department, University of Connecticut, 1084 Shennecossett Road, Groton, CT, 06340-6048 

U.S.A. 

Point of Contact: scheifel@uconn.edu
i 

CONTENTS 

TOPIC PAGE

Abstract................................................................................................................... ii

Introduction............................................................................................................. 1 

 Noise Pollution and Marine Mammals ............................................................. 1 

 Stellwagen Bank National Marine Sanctuary................................................... 3 

Historical Context ................................................................................................... 4 

 Ambient Noise .................................................................................................. 5 

 Components of Ambient Noise......................................................................... 6 

 Variability of Ambient Noise............................................................................ 8 

 Measurement of Underwater Sound and Surrounding Issues........................... 10 

Noise Level Data..................................................................................................... 12 

 Upper St. Lawrence River Estuary (Marine Park)............................................ 12 

 Stellwagen Bank National Marine Sanctuary................................................... 14 

Vessel Traffic in Stellwagen Bank National Marine Sanctuary ............................. 18 

Current Issues of Concern Regarding Noise in the Sanctuary................................ 19 

Management............................................................................................................ 20 

Literature Cited ....................................................................................................... 21 
ii 

ABSTRACT 

Although ambient (background) noise in the ocean is a topic that has been widely 

studied since pre-World War II, the effects of noise on marine organisms has only been a 

focus of concern for the last 25 years. The main point of concern has been the potential 

of noise to affect the health and behavior of marine mammals. The Stellwagen Bank 

National Marine Sanctuary (SBNMS) is a site where the degradation of habitat due to 

increasing noise levels is a concern because it is a feeding ground and summer haven for 

numerous species of marine mammals. Ambient noise in the ocean is defined as “the 

part of the total noise background observed with an omnidirectional hydrophone.” It is 

an inherent characteristic of the medium having no specific point source. Ambient noise 

is comprised of a number of components that contribute to the “noise level” in varying 

degrees depending on where the noise is being measured. This report describes the 

current understanding of ambient noise and existing levels in the Stellwagen Bank 

National Marine Sanctuary. 
1 

Introduction 

Ambient noise in the ocean is a topic that has been widely studied since the 1940s. Over 

the last 25 years the effects of noise on marine organisms has become a concern. The 

primary issue has been the potential of noise to adversely affect marine mammals. The 

Stellwagen Bank National Marine Sanctuary (SBNMS) and upper estuary of the St. 

Lawrence River are sites where the degradation of habitat due to increasing noise levels 

is a concern because they are feeding grounds and summer havens for numerous species 

of marine mammals. In an effort to provide information for better sanctuary management 

this report describes the current understanding of ambient noise and existing levels of 

ambient noise and its relationship to marine mammals in the Stellwagen Bank National 

Marine Sanctuary and the designated marine park area of the Upper St. Lawrence River 

Estuary. 

Noise Pollution and Marine Mammals 

Noise is defined as “unwanted sound” (Au, 1993). As such, the ability to quantify noise 

levels (NL) is important to any sonar system, be it anthropogenic or biotic. The purpose 

of any sonar system is to detect signals in noise. The measure of this ability is critical to 

all sonars and is measured as the ratio of the signal of interest to the noise level. This is 

commonly known as the signal-to-noise ratio or SNR. For this and other reasons, 

ambient [background] noise in the ocean is a topic that has been widely studied since 

pre-World War II. The effects of noise on marine organisms, however, has only been a 

focus of concern for the last 25 years, the main concern being its potential effects on 

marine mammals. It was this issue that led the National Research Council to create the 

Committee on Low-Frequency Sound and Marine Mammals in 1992 (NRC, 1994). The 

committee’s charge was to “review the current state of knowledge and ongoing research 

on the effects of low-frequency [0.1 to 1kHz] sound on marine mammals and to advise 

the sponsors of the report about the effects of low-frequency sound on marine mammals” 

(NRC, 1994). 

The committee was able to find virtually no quantitative information regarding noise that 

could be of use in assessing the effects of noise on marine mammals. Since that time, 

interest in the effects of noise on commercial species of fish and benthic organisms has 

grown, yet information remains sparse. Perry (1998), however, compiled an excellent 

review of the various reports regarding potential impacts of anthropogenic noise on 

cetaceans. 

Among cetaceans, coastal species are most immediately affected by human disturbance 

that degrades or destroys their habitat. Noise pollution is a factor that is only recently 

becoming recognized as a significant potential danger. Cetaceans, especially small 

gregarious Odontocetes, make extensive use of sound in their daily lives. Sounds are 

used for social communication, to ensure pod cohesion, navigation, and detecting, 

identifying and capturing prey. It has long been recognized that Odontocetes and 

Mysticetes are highly sensitive to sound and compared to humans, can receive and emit 

acoustic signals over a very wide frequency spectrum. 

 
2 

Worldwide it is estimated that there are 295 communities in 65 countries that support the 

majority of whale watching activities, leading to considerable seasonal increases in the 

density of small to large size boat traffic (Hoyt, 1994, 2001). In addition, many such 

areas are in the vicinity of sites also used for other vacationing purposes, which 

contribute additional traffic. The propulsion systems of these various crafts are a major 

source of low-frequency underwater noise that travels over considerable distances. The 

major whale watching areas are precisely those favored by the whales for feeding, 

socializing, resting, or even calving and rearing of young. Therefore, there may be the 

potential for excessive background noise to interfere with the biology of several species, 

especially where populations are restricted within such areas. The impacts of noise may 

have consequences for the whales' ecology (affecting animal energetics), physiology and 

health (audiologically or neurologically related), acoustics (affecting the structure and 

use of sounds as they relate to the acoustic environment), anatomy (affecting hearing 

organs) or some combination of these (Scheifele et al., 2004). 

Acoustic behavioral changes relative to sound levels and reverberation have shown that 

cetaceans change their signal structure to accommodate differences in acoustical 

environments (Au, 1993; Scheifele, 1988a; Scheifele et al, 2004) and in the presence of 

boat traffic (Lesage, 1993) but the limits, if any, to which they can adapt to increasing 

noise levels is unknown. Studies of audiology have shown that mammalian hearing can 

certainly be impaired by increases in sound levels (Fay, 1988; Ketten and Wartzok, 

1990). Because the basic structure of the whale ear is similar to that of land mammals, it 

is likely that they sustain substantial hearing loss with age, trauma, disease, and exposure 

to organo-toxins. However, it is also possible that aquatic ear adaptations, which protect 

against baro- or impact trauma, ameliorate noise or degenerative loss. There is an 

extensive body of research on how hearing in mammals is lost from exposure to noise, 

disease, and chemical agents. Changes that occur in the ear anatomy that are diagnostic 

for each type of impact are well documented. 

While some data suggest Odontocete ears may be somewhat resistant to hearing damage, 

it is clear from other studies that they are not impervious. Ears from humpbacks that 

survived underwater explosions, but died later from non-auditory causes, clearly had 

extensive auditory trauma that were consistent with permanent and profound hearing 

loss, including temporal bone fractures, ruptured round windows, and ear drum lesions 

(Ketten et al., 1995). These data show that adaptations that prevent barotrauma do not 

provide immunity from severe pressure trauma; therefore, it remains open what 

pressures at what frequencies will induce precipitous, irreversible damage to whale ears. 

In addition, there is evidence that suggest dolphins can lose hearing from long-term 

exposures to relatively low-level stimuli. In a second pilot study, inner ears from a longterm captive dolphin with a documented high frequency hearing loss were examined 

after the dolphin's death for pathologies related to the loss (Ketten et al., 1995). CT, 

MRI, and histological studies of these ears showed cell loss and laminar consistent with 

presbycusis, the progressive sensorineural hearing loss that accompanies old age in 

humans (Ketten et al., 1995). The primary mechanism behind presbycusis is cellular 

fatigue from cumulative noise exposures; that is, repeated exposures to sound induce 

temporary threshold shifts (TTS) that with time produce a permanent hearing loss. The 
3 

captive dolphin had normal hearing in earlier behavioral audiograms and had no known 

history of high noise exposure. The location, nature, and degree of neural degeneration 

in its ears showed a substantial, progressive, hearing loss that began in the high 

frequency regions of the ear. This too is consistent with the pattern commonly observed 

in humans (Ketten et al., 1995). 

Blind frequency-position estimates of the elder animal's hearing loss (without prior 

knowledge of the precise audiogram) predicted a profound loss for all frequencies >58 

kHz. Available records show that over a 12-year period, the dolphin's responses shifted 

from normal responses for all frequencies up to 165 kHz to no functional hearing over 60 

kHz at age 28. For this animal at least, there is a clear indication that significant hearing 

loss occurred that is attributable to cumulative, noise induced changes that occur in the 

ear with age. Finally, in a related study of 39 ears from both captive and wild marine 

mammals, evidence was found for both active infections and permanent inner ear 

damage, which was consistent with previous labyrinthine disease. In other words, 

despite any inherent evolved resistance to TTS, noise at some level and some form of 

pathologic agents can produce temporary to profound hearing loss in dolphins and 

whales. 

Stellwagen Bank National Marine Sanctuary 

The point of concern before the National Marine Fisheries Service and the Sanctuaries 

Division of NOAA is precisely the potential adverse effects that high noise levels may 

present to the cetacean species inhabiting the Stellwagen Bank National Marine 

Sanctuary (SBNMS). The SBNMS is a major cargo-shipping route and holds a number 

of marinas and major harbors. The central part of that range is seasonally dedicated to 

whale watching and recreational activities. In the summer season, numerous daily trips 

are made to the whale watching grounds (including the National Undersea Research 

Center and the North Atlantic and Great Lakes (NURC NA&GL) Aquanaut Program 

monitoring sites). In addition, ferries, small pleasure craft and fishing vessels use these 

same waters every day. Noise pollution has recently been recognized as a potential 

limiting factor in sustaining the yearly whale population in the SBNMS. 

The SBNMS being a feeding ground and summer haven for numerous species of marine 

mammals and commercial fish species is a natural site where concern over the 

degradation of habitat due to increasing noise levels is appropriate. Moreover, the 

SBNMS management staff, National Marine Sanctuaries Division, National Marine 

Fisheries Service (NMFS) and National Oceanic and Atmospheric Administration 

(NOAA) national offices have all expressed concern that rising noise levels in the 

SBNMS could be detrimental to the organisms that inhabit the bank. They are also 

concerned that increasing noise levels in both the oceans and coastal areas constitute a 

current trend of serious magnitude. 
4 

Historical Context 

The body of acoustical research regarding ambient noise in the oceans is extensive, 

having begun in the late 1940s (Knudsen et al., 1948) and continuing today (Clay and 

Tolstoy, 1987;George, 2000). Ambient noise in the ocean is defined as “the part of the 

total noise background observed with an omnidirectional hydrophone, which is not due 

to the hydrophone and its manner of mounting called “self-noise” or to some identifiable 

localized source” (Urick, 1983). It includes anthropogenic, biological, meteorological, 

hydrographic and seismic sources. Quantitative assessments of ambient noise have been 

relatively easy to accomplish (Anderson, 1958; Wenz, 1962; Greene and Buck, 1964; 

Fox, 1964; Urick et al., 1972; Nichols, 1979). In the past, the study of noise in the sea 

was of interest, primarily for military purposes. In the early 1970s the concern shifted to 

the effects of noise on marine organisms and specifically marine mammals (Payne and 

Webb, 1971; Reeves, 1977; Myrberg, 1978; Acoustical Society of America, 1981). 

Since that time the global economy has significantly changed causing the merchant fleet 

to expand accordingly. The world’s military fleets have also expanded. The advent of 

eco-tourism has caused whale watching, nature tour vessels, cruise ships, and 

commercial fishing fleets to increase as well in recent years. Moreover, the size and 

hull-types of vessels have changed since 1970. Supertankers, cannery vessels, larger 

Fleet Ballistic Missile (FBM) submarines and fast Frigates have all been added to the 

world fleet. Recently twin-hulled fast (jet wash) catamarans have begun to come on-line 

as ferries and whale watching vessels. 

All of these additional vessels along with the accompanying changes to hull-power plant 

and propeller configurations have undoubtedly increased the noise level in the oceans. 

Offshore drilling, construction and scientific research have all added to the milieu, as 

have changes to advanced military sonar systems. The use of acoustic harassment 

devices is creating additional noise. It has been estimated that oceanic noise has risen by 

some 10 decibels in a span of 25 years (NRDC, 1999); however, this figure is purely 

conjecture. 

In accordance with the Marine Mammal Protection Act of 1972 and the Endangered 

Species Act of 1973 the National Marine Fisheries Service (NMFS) is considering the 

use of a “180 dB re 1 uPa criterion” as a sound level, above which adverse effects on 

marine mammals would likely occur. The criterion would be used to limit acoustical 

operations and research in U.S. waters. This criterion is being revisited from at least two 

major perspectives. First, this would encompass all underwater activities. Second, the 

actual effects on the hearing and behavior of marine mammals are unknown at this level. 

The latter is based upon a number of studies conducted on various species of Cetacea 

(Malme et al., 1984; Richardson et al., 1986; Miles et al., 1987; Scheifele et al., 1999; 

Ljungblad et al., 1988; Richardson and Malme, 1993). In 1994 discussions regarding the 

effects of noise on the behavior of marine mammals became official with amendments to 

the Marine Mammal Protection Act that affected scientific research permits (NRDC, 

1999). 
5 

In 1994 the National Research Council suggested that a list of habitat areas currently 

exposed to high levels of anthropogenic noise be compiled. The National Resources 

Defense Council (NRDC) has compiled a preliminary list. One of the “acoustical 

hotspot” sites identified by this report is the Great South Channel. No further effort has 

been expended on updating or maintaining such a list by any federal agency to date. 

Very little research is currently being done on identifying significantly noisy sites, 

determining actual noise levels in the oceans (and particularly coastal zones), 

determining the actual physical effects of noise on various marine organisms or 

determining behavioral effects as the result of noise. Research within a few of the 

already designated sites is also scarce although it continues in the St. Lawrence River 

estuary and within the SBNMS (Scheifele et al., 1999). Moreover, issues regarding the 

measurement of noise, hearing in marine organisms, appropriate scales to use in the 

measurement of noise and hearing, acoustical behavior of marine organisms and the 

impacts of anthropogenic noise remain unresolved with few quantitative results to 

resolve them. 

Ambient Noise 

Ambient noise is an inherent characteristic of the medium having no specific point 

source. It is comprised of a number of components that contribute to the “noise level” 

(NL) in varying degrees depending on where the noise is being measured. The noise 

level is a measure of intensity however, it is practically calculated as the rms pressure of 

a plane wave relative to a reference pressure of 1 uPa in 1 Hz frequency bands across 

some spectrum (Urick, 1983). In the case of underwater sound the reference intensity 

commonly used is 1 uPa. Acoustic intensity is the primary measure of sound at any 

given frequency. 

NL = 10 log I/Iref

The term acoustic intensity infers a measure of power per unit area. Intensity is 

proportional to the mean squared pressure or rms pressure. Since hydrophones actually 

sense pressure and translate pressure fluctuations into voltages (which can be displayed 

by electronic devices such as spectrum analysers), pressure measurements are of great 

importance. The accepted reference pressure is used as the standard to proportionalize 

the actual pressure registered by the hydrophone. This quantity is the NL. Specifically, 

the NL of interest in underwater acoustics is the background or ambient noise level. 

The precise measurement of ambient noise can be a difficult task since all self-noise of 

the measuring hydrophone must be quantitatively accounted for. Nevertheless, with 

some care ambient noise levels may be determined without the use of overly elaborate 

equipment (Au, 1993). Ambient noise characteristics differ at different frequencies and 

under varying conditions. It is highly variable in shallow water where the primary 

sources of noise (such as meteorological, hydrographic, or anthropogenic sources) change 

and the dominant source (at that time) drives the frequency spectrum and associated noise 

level. Measurements taken in bays and harbors indicate that anthropogenic noise, 
6 

biologics, and tidal noise add to the sources that normally contribute to deep water 

ambient noise levels to create a more noisy acoustic environment (Anderson and Gruber, 

1971; Scheifele et al., 1997; Scheifele and Michaud, 1999). Generally the noise field in 

coastal waters tends to be dominated across the spectrum by wind speed and wave height 

(Piggott, 1965). The exception to this is during times when vessel traffic or biologics, 

such as whales, are present. 

Components of Ambient Noise 

Ambient noise varies greatly across a broad frequency spectrum from 1 Hz to 100 kHz. 

This variation is the result of erratic conditions due to various sources that may dominate 

specific parts of that spectrum (Wagstaff, 1973). These sources include: tides, 

hydrostatic effects of waves, seismic disturbances, turbulence, anthropogenic 

disturbances, thermal noise, meteorological disturbances, biologics, and absorption and 

reflection characteristics. The latter sources are specifically applicable to shallow 

waters. Analysis of fluctuations in ambient noise shows that the overall frequency 

spectrum usually consists of two frequency domains of different physical character 

(Furduev, 2000). The low-frequency realm is controlled by variations in wind speed 

while the high-frequency sector is governed by surface scatter (Furduev, 2000). 

The low-frequency end of the spectrum can be dominated by changes in hydrostatic 

pressure that result from tides and currents. Tides and currents can cause flow-induced 

noise that can be difficult to predict. In addition, tides produce changes in water 

temperature that are read by piezoelectric hydrophones as changes in pressure (Urick, 

1983). Hydrostatic pressure changes caused by waves and currents are sources of noise 

at the surface and at depth. The hydrostatic pressure changes that occur on the bottom 

are also a function of bottom type and topography. 

Another source of very low frequency (infrasonic) noise below 1 Hz is seismic 

disruption. This noise source is particularly relevant to deep ocean environments. It can 

be the result of the “normal” seismic unrest of the earth or of transient seismic events 

such as earthquakes and volcanic activity. Since the frequencies emitted by these events 

are very low the noise may be transmitted over very long distances. 

Turbulence describes an irregular flow of water in the form of random currents. These 

currents may be deep or shallow and occur in many forms such as eddies and 

longitudinal flows. They consist of rapid and significant pressure changes whose effects 

may be felt at great distances from the turbulent flows themselves. Although the 

radiated component of turbulent flows is of little significance acoustically the noise 

within the currents is of significance. The resulting pressure changes are highly varied 

(Wenz, 1962). As with seismic disturbances, turbulence has a greater effect on deep 

ocean noise than in shallow waters. 

Still another source of ambient noise is thermal noise, which can limit the sensitivity of a 

hydrophone in measuring noise levels. Thermal noise is the result of the molecular 
7 

interactions occurring in seawater (Mellen, 1952). Thermal noise is most likely to 

impact infrasonic (less than 20 Hz) frequencies. 

Between 500 Hz and 25 kHz the ambient noise spectra is dominated by the effect of 

wind and surface waves. This was observed by Knudsen et al. (1948) as early as 1947. 

Wind has a direct effect on sea state. This, in turn, has a direct correlation to the noise 

level. Although sea state can be used to get a general idea of noise level, it is difficult to 

estimate, thus wind speed is a better parameter to use. The increase in noise level 

correlated with wind speed can be broken down into a number of processes. Wind 

blowing over the sea surface generates surface waves which increase surface scatter and 

flow noise (Isakovich and Kuryanov, 1970). This produces turbulent pressure, which is 

transmitted to water. The generation of whitecaps is a process that produces hydrostatic 

noise, which is also transmitted below. Finally, the collapse of the bubbles from the 

surface waves and whitecaps causes surface cavitation in the air-saturated surface water 

(Leighton, 1994; Furduev, 1966). 

Yet another meteorological source of noise is rain. Clearly, the ambient noise level will 

be affected to an extent that directly correlates with the rate of rainfall. This effect has 

been documented (Heindsman et al., 1955; Franz, 1959; Bom, 1969) and has its greatest 

impact between 1 kHz to 20 kHz. 

A source of ambient noise that is especially important in shallow waters is biologics. 

These sounds may be intermittent or constant depending upon geographic location. The 

term biologics refers to sounds produced by organisms be they mammals, fish or 

invertebrates. These sounds are highly varied and have been studied extensively 

(Tavolga, 1964). Nearly the entire frequency spectrum from 5 Hz to 100 kHz can be 

affected by sounds of biological origin. 

Anthropogenic, or man-made, noise has become the main source of concern as a 

contributor to elevated ambient noise levels in the oceans in recent years. Many consider 

it to be the principal source of noise in the oceans (NRDC, 1999). Anthropogenic noise 

is especially conspicuous in shallow, coastal waters, harbors, and embayments 

(Scheifele, 1997). Anthropogenic noise can be generated by a wide variety of activities 

including vessels of all types, construction, military events, offshore oil exploration, 

scientific undertakings, the use of acoustic harassment devices (AHDs), and dredging 

operations. Although military and scientific operations have become the focus of 

attention recently, the dramatic increase in vessel traffic is particularly insidious world 

wide and particularly in the SBNMS. 

Anthropogenic noise, specifically vessel traffic, tends to dominate the noise levels in the 

50 to 500 Hz frequency band. This can include traffic as distant from the recording site 

as 1,000 miles. It can affect frequencies as high as 10 kHz and is especially problematic 

at frequencies around 100 Hz and has led to the development of very effective 

propagation models (Burkhalter, 1993). Of all the anthropogenic sources of noise, vessel 

traffic is the most dynamic, not only due to the number of vessels in operation at any one 

time but to the size, propulsion configuration, duty cycle and purpose of the vessels. 
8 

The advent of super tankers has led to dramatically increased levels in ambient noise. 

The world merchant fleet accounts for a major portion of the noise field in both the deep 

ocean and coastal waters. The increase in popularity of eco-tourism has heralded the 

increase in whale watching fleets with a subsequent seasonal increase in noise within 

certain sectors of coastal waters including the SBNMS. Commercial and private fishing, 

including draggers, has also advanced the noise levels in fertile fishing grounds 

including the Gulf of Maine. A plethora of private and commercial pleasure vessels may 

cause seasonal increases in noise level, although to a lesser extent than the other sources. 

Figure 1. A comparison of noise sources versus frequency ranges of each source 

comprising ambient noise. 

Variability of Ambient Noise 

Ambient noise has been shown to be highly variable (Knudsen et al., 1948; Ross, 1976) 

by as much as 20 dB re 1 uPa per day or even within shorter periods of time as shown by 

Richardson et al. (1995). Variations in the component sources of ambient noise are 

partially responsible for the irregularities and constant changes in the overall ambient 

noise level. Variations in sound transmission conditions are also responsible for these 

irregularities and changes. The better the propagation conditions the higher the noise 

level because the sound will attenuate slowly with distance. The sea is an excellent 

medium for the transmission of sound albeit a very complex one. The many diverse 

effects on the distribution of underwater sound are due to transmission losses in the 

medium. 

Transmission loss (TL) is defined as the deterioration of an acoustic signal between a 

source and a receiver. In the case of ambient noise it is taken to be a general weakening 

of the overall noise level given that ambient noise, in and of itself, is not considered to be 
9 

a point source but a property of the medium. Transmission loss is a general term 

representing the sum of spreading, attenuation, and refraction losses (Urick, 1983). 

Spreading refers to the weakening of sound as it travels away from a source. With 

respect to ambient noise, it pertains to that portion of the noise field measured at a 

distance from one or more of the components such as seismic events, storms, shipping or 

biologics. Spreading is quantified as a function of geometry with respect to the source. 

In deep water or within the surface/bottom boundaries of a body of water (referred to as 

one water-depth) the sound will radiate from the source in all directions as a sphere. 

This is known as spherical spreading and the rate of decay of sound can be calculated 

outward from the source to a distance of one water-depth as: 

TL = 20 log r 

where TL is taken to be spherical spreading loss and r is the radial distance from the 

source. 

Once the radial distance equal to one water-depth has been reached from the source, the 

surface and bottom boundaries interfere (since the sound cannot cross the boundaries) 

and spherical spreading is no longer able to take place. At this point cylindrical 

spreading occurs and the subsequent decay of sound is calculated as: 

TL = 10 log r 

where TL is taken as cylindrical spreading loss and r remains the radial distance from the 

source as before. Total transmission loss is the sum of spreading, attenuation, and 

refraction losses. 

Attenuation loss refers to the decay of sound, as it travels from the source, due to 

chemical and physical phenomena. These primarily include absorption and scattering. 

The calculation of attenuation losses tends to be complex and continues to be extensively 

studied and modeled. Absorption represents the loss of sound due to transfer of 

mechanical (acoustic) energy into heat as both mechanical and chemical reactions 

(Liebermann, 1948). Three specific reactions have been well studied: shear viscosity by 

Rayleigh (1945), volume viscosity by Mason (1965), and ionic relaxation by Leonard et 

al. (1949), Schulkin and Marsh (1962), Mellen, et al. (1988a, 1988b) and Scheifele, et al. 

(1988a, 1988b). A complete synopsis of this research can be found in Urick (1983). An 

additional physical impact on acoustic attenuation is the sound velocity structure of the 

water column. 

Sound velocity varies as a function of temperature, salinity and pressure at any given 

location. In general, sound velocity increases with increasing temperature, salinity and 

depth and can be measured in the field using a CTD (conductivity, temperature, depth) 

device. Based on these three parameters, a sound velocity profile may be derived. This 

profile will vary with latitude, season, and time of day. At some locations the acoustic 

structure of the water column will be stratified as shown in the sound velocity profile, 
10 

due to temperature, salinity and pressure. Of the three parameters, temperature is most 

likely to have the greatest effect on stratification of the water column. 

Stratification of the water column can cause acoustic zones or sound channels to occur. 

These may be either deep or shallow. The best known of these is the SOFAR (Sound 

Fixing And Ranging) channel. The SOFAR channel has a minimum depth of 4,000 feet 

and is sometimes known as the deep sound channel. At the surface, water is warmed by 

the sun and mixed by surface wave action to form a surface or mixed layer. Sound is 

often trapped in this layer creating a surface duct in which sound can travel very well 

over long distances. 

In shallow water where sound is reflected from both the surface and the bottom, a 

shallow water channel may exist. In this case, acoustic characteristics of the surface and 

bottom influence the sound field. The sound will propagate over distances at least 

several times greater than the water depth. This occurs in coastal waters less than 500 

feet deep (McLeroy, 1986). 

Refraction loss refers to the distortion and instability of sound in relation to boundaries 

such as the surface and the bottom. Sound can be absorbed or reflected by different 

bottom substrates. The more porous the sediment, the more sound will be absorbed. On 

the other hand, noise levels may fluctuate greatly at the sea surface due to reflections 

from constantly changing wave faces. Ambient noise levels in hard bottom (highly 

reflective) locations tend to be high (Staal, 1992). 

The calculation of transmission loss for practical purposes is complex at best. With 

respect to ambient noise levels, transmission loss may play less of a role than the source 

components, however, it is a major factor in determining the propagation of the noise 

from each of those sources (Staal, 1992; Zakarauskas, 1990). A clear understanding of 

transmission loss characteristics in the SBNMS is critical toward the enactment of 

decisions relating to the treatment of noise within its boundaries. 

Measurement of Underwater Sound and Surrounding Issues 

Acoustic intensity is the fundamental measure of the propagation of sound (Kinsler et al., 

1982). Although acoustic intensity is of interest to acousticians and engineers it is not 

useful in a practical sense. Recall that acoustic intensity infers a measure of power per 

unit area. For practical reasons (largely due to equipment limitations) it is pressure that 

is measured and reported. This measurement is known as the Sound Pressure Level, or 

SPL. Intensity is proportional to the mean squared pressure or rms pressure, therefore, a 

ratio of pressures is used to quantify and report SPLs. 

SPL (dB re 1 uPa) = 20 log P/Pref 

This logarithmic measure of acoustic pressure is known as the decibel (dB). 
11 

Quantitative measurements of sound pressure should always include the pressure to 

Which the measure is being referenced. For underwater measurements the reference 

pressure is 1 micro Pascal. One issue in acoustics is that researchers are not always 

conscientious about reporting reference units (Richardson et al., 1995). Using the 

decibel as a unit of measure of intensity is convenient mathematically and has a number 

of advantages. It provides a common scale for expressing intensities, it can 

accommodate a wide range of intensity values (which are normally encountered in 

acoustics), and it simplifies the mathematics of calculating acoustic measurements. 

There are however, issues surrounding the use of the decibel when the measurements are 

intended for use in discussing hearing. 

The research and lay communities are more familiar with the measurement of airborne 

sounds. While the reference pressure for underwater sound is 1 uPa, the reference for 

airborne sound is 20 uPa (Kinsler et al., 1982; Stevens and Davis, 1983). In addition, 

airborne sounds measured with respect to hearing are often expressed in reference to 

human hearing. In these cases they are manipulated or weighted to enable medical 

doctors, audiologists, speech pathologists and acoustical engineers to more closely 

analyze the sounds with respect to the human “best range of hearing.” An “A-weighted” 

system of measurement is used which de-emphasizes frequencies below 1 kHz and 

above 6 kHz (Dobie, 1993; Durrant and Lovrinic, 1995). Using the decibel has lead to 

the mistake of falsely equating airborne noises, in different frequency bands, to one 

another and worse (more recently) to underwater sounds (NRDC, 1999). 

 

Mathematics and physics do allow for conversion of sound levels from one reference and 

medium to another (as in the case of air and water). Sound pressure levels (SPLs) are 

measured in decibels as the ratio of pressures however, it is best to compare intensities 

because pressure effects between the air and water media are different. Equating 

intensities may be done as follows: 

 

 Ia = p

2

a / ρa ca = Iw = p

2

w / ρw cw 

where a represents in-air and w represents in-water. Given, that ρa ca = 416 Pa.s/m and 

that ρw cw = 1.5 x 106

 Pa.s/m then pw = 60 Pa where pw and pa are in Pascals. Now 

convert to uPa by multiplying by 106

. Therefore, 

 SPLa = 20 log (pa x 106/20) and SPLw = 20 log (pw x 106) 

 and 

 SPLw = SPLa + 20 log (60 x 20) = SPLa + 62 dB 

This accounts for the impedance difference between air and water and gives a true 

conversion from an in-air to in-water values (Scheifele, 1997). Oceanographers 

routinely do this however, such comparisons are not meaningful with respect to 

comparing the impacts on hearing in marine organisms versus terrestrial ones (Smith, 

1985). It is also unacceptable if one is comparing the effects of noise on animals with 

different hearing sensitivities. For an up-to-date treatment of this issue and its relevance 

to anthropogenic noise see Richardson et al. (1995). 
12 

Noise Level Data 

It is a matter of debate whether noise levels in the oceans have significantly increased. It 

seems unquestionable that an increase has occurred over the last 25 years but it is nearly 

impossible to quantify the change. Few noise-monitoring programs exist. Two 

programs of interest are in progress: acoustic monitoring of the Saint Lawrence River 

Estuary in the Tadoussac region of Quebec, Canada, and a summer monitoring program 

in the Stellwagen Bank National Marine Sanctuary. Both programs take place during 

peak summer months so that the data are scarce but consistent by site and time of year. 

The data are taken during the peak whale watching and pleasure boat season. These will 

be discussed in the following sections. 

Upper St. Lawrence River Estuary (Marine Park) 

Ambient noise samples have been taken by Scheifele et al. (1997) and Scheifele (1997) 

at four discrete hours per day at three sites where beluga whales are known to congregate 

near Tadoussac Harbor, Quebec, Canada. The samples are taken in summer when vessel 

traffic is at its highest. The traffic consists of ferries, merchant vessels, whale watching 

vessels, private and government craft. To date, 3,600 samples have been taken and 

analyzed. Mean noise levels at frequencies of 500 Hz, 1kHz, 10 kHz, and 40 kHz are 

compared to hearing sensitivity curves for belugas. No such curves exist for any 

Mysticete species. The selection of sites, all near the confluence of the Saguenay River 

and the St. Lawrence Estuary, were made in view of their: 

1. differing vessel traffic and use patterns causing distinct background 

noise intensities; 

2. regular use by different beluga social groups during the same portion 

of the summer range (in an effort to reduce confounding factors due 

to differences among whales of different social groupings and/or of 

different areas); 

3. intrinsic quality of the site's acoustical environments (topography, 

depth); 

4. proximity to one another and, hence, ability to sample them numerous 

times during a single day. A map is shown on page 14. 

Site 1. Saguenay site (48o

 07.34'N, 69o 41.40'W) is located approximately 1 km outside 

of the harbor of Tadoussac at the mouth of the Saguenay fjord. The water depth is 100 

m and the area is heavily used by vessel traffic including frequent passage of three Bay 

St. Catherine-Tadoussac ferries (approximately every 20 minutes), passage of large 

merchant ships traveling up the estuary, daily whale watching traffic from June to 

October, and numerous recreational and work vessels. The belugas that pass through this 

area typically travel in pods of adults accompanied by juveniles (Michaud, 1993). The 

animals typically feed near this area and pass through en route to sites up the Saguenay 

River. 
13 

Site 2. The Channel Head site (48o

 67.83'N, 69o 33.38'W) is located approximately 8 km 

east of the Saguenay site on the north side of the St. Lawrence estuary. The site (water 

depth 120 m) is located near an important upwelling and current confluence and is 

believed to be an important feeding site for belugas, fin whales, and minke whales . 

Three general types of social groups inhabit these areas: mature males, females and 

females with young, and young males. This site is used by three social groups of beluga 

and these groups often travel from site 1 to site 2 or reverse. It is the area of the largest 

concentration of belugas. The area, located on the Saint Lawrence shipping lane, is also 

a core area for whale activities. As many as 250 individuals, close to half the population, 

can be found daily at this site during the summer. Because this area also supports 

several other whale species (fins, minkes), it represents an area affected by whale 

watching vessels. It is also affected by the regular passage of merchant vessels. 

Site 3. The Alouette site (48o 02.56'N, 69o 40.71'W) is located 8 km west of the 

Saguenay site on the south side of the St. Lawrence River. The water is shallow (40 m) 

and subject to moderate tidal currents. This site is less affected by vessel traffic than the 

other sites with the majority of traffic consisting of the sporadic passage of merchant 

vessels. The data (thus far) indicate that mean noise levels are nearly the same between 

years. 

Figure 2. Map of acoustic sample sites in St. Lawrence River Estuary Monitoring 

Program. 
14 

Stellwagen Bank National Marine Sanctuary 

Over the last four years, ambient noise samples have been collected at six sites in the 

SBNMS. Personnel from the National Undersea Research Center and the North Atlantic 

and Great Lakes Aquanaut Program took these samples in summertime. In addition, one 

sample was taken by Scheifele in September 1998. 

Site designations are shown in Figure 3 and Table 1. These positions are representative 

of prime whale watching sites that are frequented by humpback, minke, and fin whales 

in summer. Private and commercial fishing operations take place in the northern sites 

within the sanctuary. The southern sites are near the shipping lane leading into Boston 

Harbour. 

Figure 3. Map of acoustic monitoring sites in the SBNMS. 

1 

2 

3 

4 

5 

6 
15 

Table 1. Locations of the SBNMS acoustic monitoring sites. 

SITE DESIGNATION LATITUDE LONGITUDE 

1 42o

 21.74’N 70o 30.32’W

2 42o

 25.153’N 70o 28.447’W

3 42o

 15.03’ N 70o 16.74’W

4 42o

 14.03’N 70o 16.00’W

5 42o

 22.00’N 70o 19.00’W

6 42o

 25.80’N 70o 26.00’W

Acoustic samples in the St. Lawrence River Estuary are taken at each site at four times 

of day: 0700, 1000, 1300, and 1600 hours. The 1000 and 1300 hour sample times 

represent the busiest span of time while the 0700 and 1600 are the quietest times at each 

end of the day with respect to vessel traffic. Samples are taken in summer, during the 

peak boating season when the greatest potential for high intensity anthropogenic noise 

exists. Each hourly sample is taken in three 15-minute duration segments to confirm 

precision of measurement (mean sound pressure level). Wind speed, sea state, 

precipitation, and tidal regime are also recorded. 

Acoustic samples are taken using an ITC-42A omnidirectional hydrophone and Ithaco 

amplifier and recorded on a Sony TCD-D8 digital audio tape recorder (DAT) for the 500 

Hz, 1 kHz and 10 kHz samples and a Lockheed Store 4D recorder operating at 60 ips is 

used for the 40 kHz samples. The DAT system has a flat response from 0.5 to 20 kHz 

and is calibrated with the hydrophone to 1 volt at 1 KHz. Hydrophone depth is 6 m for 

all samples. The hydrophone has a free-field sensitivity of -188.2 dB for 500 Hz and 1 

kHz, -191.1 dB for 10 kHz, and -206.6 dB at 40 kHz. The response is flat to 80 kHz. 

The recordings are analyzed on a Hewlett-Packard 3562A spectrum analyzer. 

As with the St. Lawrence River Estuary, samples at the SBNMS are taken in summer, 

during the peak boating season with the greatest potential for high intensity 

anthropogenic noise. Wind speed, sea state, precipitation, and tidal regime are recorded. 

Bottom type is assessed by 150 m video transects taken with a MaxROV. Sediment 

samples are also taken and sieved to determine grain size and porosity in an effort to 

determine basic bottom reflectivity in accordance with Frisk (1980), Dodds (1980), Akal 

(1980), and Urick, (1983). Contributions of vessel traffic and biologics are extrapolated 

from radar and the use of maneuvering boards. Acoustic samples are recorded for 50 

Hz, 100 Hz, 150 Hz, 500 Hz, 1 kHz, 10 kHz, and 20 KHz samples. 

There are preliminary indications that within the St. Lawrence River Estuary the 

Allouette (site 3) is generally quieter than both the Saguenay (site 1) and Channel Head 

(site 2) sites. Channel Head tends to be the noisiest site. Noise levels at the Saguenay 

and Channel Head sites are highest at 1000 and 1300 hours at 500 Hz, 1 KHz, and 10 

KHz with the noise levels at 0700 and 1600 hours being similar but of lower intensity. 

At the other frequencies there are exceptions to the time of peak noise. It can also be 
16 

seen that for frequencies below 40 KHz the noise levels are highest at the Channel Head 

site followed by the Saguenay site at 500 Hz and 1 KHz, with the Allouette site being 

much quieter than either of the first two except at 10 KHz. Table 2 shows mean noise 

levels (from Scheifele et al., 1999). 

Table 2. Mean ambient noise levels at Saint Lawrence River Estuary sites (from 

Scheifele et al., 1999).

Marginal

Site 7:00 10:00 13:00 16:00 Mean

Saguenay 1 136.5074 143.6337 144.2471 141.6548 141.5108

Channel Head 2 135.9819 143.9204 147.3961 142.3131 142.4029

Allouette 3 133.4438 140.7552 144.0003 139.9436 139.5357

Marginal Mean 135.311 142.7698 145.2145 141.3038

21 dB for 1/3-octave

Site 7:00 10:00 13:00 16:00

Saguenay 1 132.7666 142.3036 145.6135 138.5639 139.8119

Channel Head 2 136.6279 142.7716 148.4151 143.2837 142.7746

Allouette 3 124.3825 140.561 144.3428 139.7212 137.2519

Marginal Mean 131.259 141.8787 146.1238 140.5229

24 dB for 1/3-octave

128.04 119.32 110.67 125.54

124.53 118.88 110.67 124.96

Site 7:00 10:00 13:00 16:00

Saguenay 102.9867 116.4744 122.182 113.4162 113.7648

Channel Head 116.4821 120.6013 121.1932 118.8025 119.2698

Allouette 96.8823 103.3884 122.024 103.7126 106.5018

Marginal Mean 105.4504 113.488 121.7997 111.9771

34 dB for 1/3-octave

115.26 122.73 132.2 132.74

110.25 124.73 133.86 134.16

Site 7:00 10:00 13:00 16:00

Saguenay 98.1247 92.1012 99.0566 93.3971 95.6699

Channel Head 86.8182 84.8913 91.2197 89.0641 87.99833

Allouette 83.3309 93.4091 83.4701 85.1234 86.33338

Marginal Mean 89.4246 90.13387 91.2488 89.19487

40 dB for 1/3-octave

 Comparison of Mean Noise levels

at Each Site Across Sample Times of Day

Noise Levels are given at selected frequencies of interest:

500 Hz - Low frequency of Beluga communications and hearing

1 kHz and 10 kHz - Within communications range

40 kHz - Beluga characteristic frequency

Marginal means are shown for comparison across sites and times.

Mean Noise Levels

dB re 1 u Pa2 at 500 Hz

Mean Noise Levels

dB re 1 uPa2 at 1 kHz

Mean Noise Levels

dB re 1 uPa2 at 10 kHz

Mean Noise Levels

dB re 1 uPa2 at 40 kHz
17 

The data from the Stellwagen Bank National Marine Sanctuary indicate that mean noise 

levels are nearly the same between years with the exception of the sites located near the 

shipping lane. Changes in ambient noise (site raw data) at other sites are largely due to 

the amount of whale watching activity occurring on the sample dates. However, the 

mean noise levels are not significantly different from year to year. Table 3 shows a 

synopsis of the few data points taken to date. The data are taken from a report given in 

1999 by the aquanauts of Sage Park School and Scheifele et al., (1999). Proofing and 

analyses are still in progress and these results are only preliminary. No statistical 

analyses have been attempted due to paucity of data. Tables 3a, 3b, and 3c show mean 

noise levels (the mean of 5 samples per site over a single day’s time) at frequencies of 50 

Hz, 100 Hz and 500 Hz only. 

Table 3a. Mean Noise Levels at 50 Hz in the SBNMS by Site (1996 – 1999); (NL in dB re 

1uPa/Hz; N = 85); (from Lobach et al. 1999). 

SITE 1996 1997 1998 1999 

1 72.46 78.57 80.65 68.59 

2 85.26 79.20 82.05 74.23 

3 87.19 88.19 89.15 86.99 

4 88.18 88.21 83.11 83.16 

5 80.28 91.23 90.79 80.26 

6 95.34 93.16 91.33 91.97 

Table 3b. Mean Noise Levels at 100 Hz in the SBNMS by Site (1996 – 1999); (NL in dB 

re 1uPa/Hz; N = 85); (from Lobach et al. 1999). 

SITE 1996 1997 1998 1999 

1 60.46 50.00 53.12 53.26 

2 43.00 58.45 55.16 56.00 

3 50.19 57.78 51.00 57.187 

4 98.58 79.49 92.02 95.97 

5 69.32 68.15 67.46 68.36 

6 98.54 90.65 91.31 80.44 
18 

Table 3c. Mean Noise Levels at 500 Hz in the SBNMS by Site (1996 – 1999); (NL in dB 

re 1uPa/Hz; N = 85); (from Lobach et al. 1999). 

SITE 1996 1997 1998 1999 

1 52.11 50.01 50.00 51.85 

2 48.00 58.99 52.00 56.20 

3 50.25 55.06 49.99 55.37 

4 78.79 72.33 72.05 75.65 

5 60.00 68.42 65.00 65.87 

6 78.99 80.22 71.15 80.64 

Vessel Traffic in the SBNMS 

In addition to the types of vessels and the shear number of them traversing the SBNMS, 

the propulsion configuration can make a great contribution to noise level and frequencies 

introduced into the water. The propulsion plant is primarily responsible for the 

frequency signature of any given vessel, but most of the additional noise comes from the 

“screw-blade configuration” and how the ship is operated. Most merchant vessels run 

with either a “single-five” [blades] or a “twin-three or five” configuration. Their 

presence and configuration are readily apparent to even the most junior sonar operator. 

Ship captains tend to run at 9 – 12 knots. At these speeds cavitation is the norm. 

Cavitation of the ship’s propeller can yield an enormous amount of noise. This has been 

well known to military sonar operators since World War II but has only recently been 

studied more closely (Leighton, 1994). Merchant vessels typically cavitate especially 

when they are inbound and fully loaded. Outbound vessels are usually light and high 

and some 1/3 of the propeller surface can be seen out of the water causing surface 

bubbles and a large wake. Cavitation has theoretically been alleviated with the advent of 

vessels using jet-wash propulsion plants, however, the problem of cavitation bubbles still 

exists, although the degree is uncertain. 

Although vessels in the shipping lane (mostly commercial) account for most of the 

distant or near field noise in the SBNMS there are some seasonal and transient 

contributions of significance. Fishing activities, specifically dragging, have caused some 

recordings to be high. These “events” are not normally consistent across samples. 

Another significant contribution at nearly all sample sites in summer is whale-watching 

activity. Although the whale watching activity in the SBNMS is not nearly as intense as 

in the St. Lawrence River Estuary it still has significant impacts on local noise levels 

during the season. A number of research groups, such as the Cetacean Research Unit 

and even the SBNMS personnel and Auster and Trimarchi (pers. comm.) have been 

observing cetacean behavior in the presence of vessel traffic yet it remains uncertain 

what, if any, impact the present noise levels may be having on the whale population of 

the bank. Preliminary analyses were conducted by Lobach et al. (1999) to compare the 

noise levels to the hearing sensitivities of the Harbour Porpoise (Phocoena phocoena) 

(Au, 1993) and Pilot Whale (Globicephala melaena) (Fay, 1988; Miller et al., 1998) do 
19 

not indicate any adverse probabilities save for potential masking effects. 

Twin-hulled, jet-propelled vessels are now being introduced for use as ferries and whale 

watch vessels. They are fast, so they are economical in the sense that they reach their 

destination sooner, allowing for more trips per day to be made. Owners and shipbuilders 

champion their cause under the guise of the ship not having a propeller. To date, little 

quantitative research has been done on the acoustics of such a vessel, although it has 

been inferred that they are actually quieter than the “traditional” propeller driven vessel. 

The issue remains as to whether they can be heard by marine mammals that are at the 

surface in enough time for the animal (or the vessel captain) to perform evasive 

maneuvers. The issue is demonstrated by a number of documented ship strikes of 

whales (Measures, 1998). 

Current Issues Regarding Noise in the SBNMS 

There is a distinct need to develop and conduct a formal acoustic monitoring plan within 

the SBNMS. Presently only NURC NA&GL at the University of Connecticut and 

Woods Hole Oceanographic Institution (WHOI) are considering plans for long-term 

acoustic monitoring including the use of buoys, arrays, and/or Autonomous Underwater 

Vehicles (AUV). Specifically, quantifiable temporal ambient noise data is needed to 

characterize the acoustic environments in all sectors of the Bank and to determine what 

contribution the shipping lane is making. Transmission loss research would also be 

useful in determining the characteristics of the acoustic environment, especially in 

sectors most frequented by whales. Likewise, more research into bottom interactions is 

needed to add to recent studies such as that of Lyons and Abraham (1999). Ship 

signature and source levels of vessels routinely operating within the confines of the 

sanctuary would be helpful especially in the case of jet-wash vessels. 

The SBNMS is an excellent location to continue bioacoustic and psychoacoustic 

(behavioural) research especially with regard to Mysticete species and the endangered 

Northern Right Whale (Eubalaena glacialis). This research should include marine 

mammal hearing (anatomical and audiological) research, marine mammal tracking and 

behavioral research. The objectives of these studies should include, but not be limited 

to, assessment of the actual exposure of the whales to anthropogenic noise in their 

natural habitat on a regular basis in the SBNMS, evaluation of the observable impacts of 

such exposure in terms of anatomical, histopathological and behavioural markers, and to 

propose adequate measures for managing and protecting other marine mammals in 

similar situations. Research regarding this topic has not, to date, taken such a multidisciplinary approach, consequently, there is much disagreement regarding the effects of 

noise pollution on whale hearing, especially when viewed from a physics/engineering 

versus biology versus psychophysical viewpoint (Mercado and Frazer, 1999). More 

research is needed on equating airborne hearing and underwater noise levels. A 

consensus must be reached regarding consistent measurement techniques and bioacoustic 

standards with respect to marine mammals. 
20 

Management 

The best that can be expected of current management is a recognition that excessive 

noise can and will present a problem to many species of organisms within the sanctuary 

and a commitment to exploring the extent to which this problem exists in the SBNMS. 

Next, there is a need to monitor the situation to determine whether the problem is 

chronic and of an increasing nature (elevating noise levels). Finally, decisions as to how 

to cope with or alleviate such potentially insidious problem must be made. This may 

even require collaboration at a federal level in the form or reforming the Marine 

Mammal Protection Act. 

In collaboration with other organizations that are now pursuing similar issues, such as 

Parks Canada and the Department of Fisheries and Oceans in Canada (Bailey and 

Zinger, 1996), information and ideas should be pooled to expedite the processes 

mentioned above. These represent minimum measures. More global measures that may 

be of interest may be found in the report by the National Resources Defense Council 

(1999). 

Richardson et al. (1986) described the assessment of the potential effects of noise on 

marine mammals as being based on specific zones of influence. These consist of four 

criteria: (1) the zone of audibility, (2) the zone of responsiveness within which an 

animal reacts to the sound, (3) a zone of masking within which the noise levels can 

interfere with other sounds or even whale signals, and (4) the zone of hearing loss or 

discomfort. This should be assessed within the context of vessel operating zones within 

the SBNMS especially with respect to whale watching. Previous studies of noise effects 

on whales have largely been based on behavior. When considering the relationship of 

noise to acoustic behavior, flight response of the animal must also be considered. Each 

animal will respond within some flight distance when it perceives a change in the 

environment (Hediger, 1964). The flight distance is a specific amount of space 

surrounding an animal in which the animal feels at rest. When a perceived source of 

danger breaches the border of the flight distance, the animal elicits some behavioral 

response. This needs to be revisited with respect to management issues relating to 

marine mammal behavior around vessels and the shipping lane in the Stellwagen Bank 

National Marine Sanctuary. 
21 

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