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Environmental risk assessment for impact pile driving requires characterization of the radiated sound field. Damped cylindrical spreading (DCS) describes propagation of the acoustic Mach cone generated by striking a pile and predicts sound exposure level (LE) versus range. For known water depth and sediment properties, DCS permits extrapolation from a measurement at a known range. Impact assessment criteria typically involve zero-to-peak sound pressure level (Lp;pk), root-mean-square sound pressure level (Lp;rms), and cumulative sound exposure level (LE;cum). To facilitate predictions using DCS, Lp;pk and Lp;rms were estimated from LE using empirical regressions. Using a wind farm construction scenario in the North Sea, DCS was applied to estimate ranges to recommended thresholds in fishes. For 3500 hammer strikes, the estimated LE;cum impact ranges for mortal and recoverable injury were up to 1.8 and 3.1km, respectively. Applying a 10dB noise abatement measure, these distances reduced to 0.29km for mortal injury and 0.65km for recoverable injury. An underlying detail that produces unstable results is the averaging time for calculating Lp;rms, which by convention is equal to the 90%-energy signal duration. A stable alternative is proposed for this quantity based on the effective signal duration

Regulations for underwater anthropogenic noise are typically formulated in terms of peak sound pressure, root-mean-square sound pressure, and (weighted or unweighted) sound exposure. Sound effect studies on humans and other terrestrial mammals suggest that in addition to these metrics, the impulsiveness of sound (often quantified by its kurtosis β) is also related to the risk of hearing impairment. Kurtosis is often used to distinguish between ambient noise and transients, such as echolocation clicks and dolphin whistles. A lack of standardization of the integration interval leads to ambiguous kurtosis values, especially for transient signals. In the current research, kurtosis is applied to transient signals typical for high-power underwater noise. For integration time (t 2 - t 1), the quantity (t 2 - t 1) / β is shown to be a robust measure of signal duration, closely related to the effective signal duration, τ eff for sounds from airguns, pile driving, and explosions. This research provides practical formulas for kurtosis of impulsive sounds and compares kurtosis between measurements of transient sounds from different sources. © 2020 Acoustical Society of America.

Previous studies exploring injury response to pile driving in fishes presented exposure paradigms (>900 strikes) that emulated circumstances where fish would not leave an area being ensonified. Those studies did not, however, address the question of how many strikes are needed before injuries appear. Thus, the number of strikes paired with a constant single strike sound exposure level (SELss) that can cause injuries is not yet clear. In order to examine this question, hybrid striped bass (white bass Morone chrysops × striped bass Morone saxatilis) were exposed to 8–384 strikes in three different SELss treatments that generated different cumulative sound exposure level values. The treatment with the highest SELss values caused swim bladder injuries in fish exposed to as few as eight pile strikes. These results have important implications for pile driving operations where SELss values meet or exceed the exposure levels used in this study.

Pile-driving and other impulsive sound sources have the potential to injure or kill fishes. One mechanism that produces injuries is the rapid motion of the walls of the swim bladder as it repeatedly contacts nearby tissues. To further understand the involvement of the swim bladder in tissue damage, a specially designed wave tube was used to expose three species to pile-driving sounds. Species included lake sturgeon ( Acipenser fulvescens )—with an open (physostomous) swim bladder, Nile tilapia ( Oreochromis niloticus )—with a closed (physoclistous) swim bladder and the hogchoker ( Trinectes maculatus )—a flatfish without a swim bladder. There were no visible injuries in any of the exposed hogchokers, whereas a variety of injuries were observed in the lake sturgeon and Nile tilapia. At the loudest cumulative and single-strike sound exposure levels (SEL cum and SEL ss respectively), the Nile tilapia had the highest total injuries and the most severe injuries per fish. As exposure levels decreased, the number and severity of injuries were more similar between the two species. These results suggest that the presence and type of swim bladder correlated with injury at higher sound levels, while the extent of injury at lower sound levels was similar for both kinds of swim bladders.

Fishes and marine mammals may suffer a range of potential effects from exposure to intense underwater sound generated by anthropogenic activities such as pile driving, shipping, sonars, and underwater blasting. Several underwater sound recording (USR) devices have been built to acquire samples of the underwater sound generated by anthropogenic activities. Software becomes indispensable for processing and analyzing the audio files recorded by these USRs. In this paper, we provide a detailed description of a new software package, the Aquatic Acoustic Metrics Interface (AAMI), specifically designed for analysis of underwater sound recordings to provide data in metrics that facilitate evaluation of the potential impacts of the sound on aquatic animals. In addition to the basic functions, such as loading and editing audio files recorded by USRs and batch processing of sound files, the software utilizes recording system calibration data to compute important parameters in physical units. The software also facilitates comparison of the noise sound sample metrics with biological measures such as audiograms of the sensitivity of aquatic animals to the sound, integrating various components into a single analytical frame. The features of the AAMI software are discussed, and several case studies are presented to illustrate its functionality.

Caged fish were exposed to sound from mid-frequency active (MFA) transducers in a 5 × 5 planar array which simulated MFA sounds at received sound pressure levels of 210 dB SPL(re 1 μPa). The exposure sound consisted of a 2 s frequency sweep from 2.8 to 3.8 kHz followed by a 1 s tone at 3.3 kHz. The sound sequence was repeated every 25 s for five repetitions resulting in a cumulative sound exposure level (SEL(cum)) of 220 dB re 1 μPa(2) s. The cumulative exposure level did not affect the hearing sensitivity of rainbow trout, a species whose hearing range is lower than the frequencies in the presented MFA sound. In contrast, one cohort of channel catfish showed a statistically significant temporary threshold shift of 4-6 dB at 2300 Hz, but not at lower tested frequencies, whereas a second cohort showed no change. It is likely that this threshold shift resulted from the frequency spectrum of the MFA sound overlapping with the upper end of the hearing frequency range of the channel catfish. The observed threshold shifts in channel catfish recovered within 24 h. There was no mortality associated with the MFA sound exposure used in this test.

This study investigated the effects on rainbow trout (Oncorhynchus mykiss) of exposure to high-intensity, low-frequency sonar using an element of the standard Surveillance Towed Array Sensor System Low Frequency Active (LFA) sonar source array. Effects of the LFA sonar on hearing were tested using auditory brainstem responses. Effects were also examined on inner ear morphology using scanning electron microscopy and on nonauditory tissues using general pathology and histopathology. Animals were exposed to a maximum received rms sound pressure level of 193 dB re 1 microPa(2) for 324 or 648 s, an exposure that is far in excess of any exposure a fish would normally encounter in the wild. The most significant effect was a 20-dB auditory threshold shift at 400 Hz. However, the results varied with different groups of trout, suggesting developmental and/or genetic impacts on how sound exposure affects hearing. There was no fish mortality during or after exposure. Sensory tissue of the inner ears did not show morphological damage even several days post-sound exposure. Similarly, gross- and histopathology observations demonstrated no effects on nonauditory tissues.

Six species of fishes were tested under aquatic far-field, plane-wave acoustic conditions to answer several key questions regarding the effects of exposure to impulsive pile driving. The issues addressed included which sound levels lead to the onset of barotrauma injuries, how these levels differ between fishes with different types of swim bladders, the recovery from barotrauma injuries, and the potential effects exposure might have on the auditory system. The results demonstrate that the current interim criteria for pile-driving sound exposures are 20 dB or more below the actual sound levels that result in the onset of physiological effects on fishes.

Many species of odontocete cetaceans (toothed whales) use high-frequency clicks (60–170 kHz) to identify objects in their environment, including potential prey. Behavioral studies have shown that American shad, Alosa sapidissima, can detect ultrasonic signals similar to those of odontocetes that are potentially their predators. American shad also show strong escape behavior in response to ultrasonic pulses between 70 and 110 kHz and can determine the location of the sound source at least in the horizontal plane. The present study examines physiological aspects of ultrasound detection by American shad and provides the first insights into the neural encoding of ultrasound signals in any nonmammalian vertebrate. The recordings were obtained by penetration through the cerebellar surface. All but two units responded exclusively to ultrasound. Ultrasound-sensitive units did not phase-couple to any stimulus frequency. Some units resembled the response of constant latency neurons found in the ventral nucleus of the lateral lemniscus of bats. We suggest that ultrasonic and sonic signals are processed along different pathways in Alosa. The ultrasonic pathway in Alosa appears to be a feature detector that is likely to be adapted (e.g., frequency, intensity) to odontocete echolocation signals.

Cockroaches ( Periplaneta americana) orient their antennae toward moving objects based on visual cues. Presumably, this allows exploration of novel objects by the antennal flagellum. We used videographic and electrophysiological methods to determine if receptors on the flagellum are essential for triggering escape, or if they enable cockroaches to discriminate threatening from non-threatening objects that are encountered. When a flagellum was removed, and replaced with a plastic fiber, deflection of a "prosthetic flagellum" still activated the descending mechanosensory interneurons associated with escape and produced typical escape responses. However, escape was essentially eliminated by constraining the movement of the scape and pedicel at the antennal base. When cockroaches approached and briefly explored the surface of a spider or another cockroach with the flagellum, they produced escape significantly more often in response to subsequent controlled contact from a spider than from a cockroach. This discrimination did not depend on visual or wind-sensory input, but required flagellar palpation of the surface. The crucial sensory cues appear to involve texture rather than surface chemicals. These results indicate that cockroaches acquire basic information on stimulus identity during exploration of surfaces with flagellar receptors, but that basal receptors are triggers for escape behavior.

The effects of loud sounds on fishes, such as those produced during impulsive pile driving, are an increasing concern in the management of aquatic ecosystems. However, very little is known about such effects. Accordingly, a High Intensity Controlled Impedance Fluid Filled wave Tube (HICI-FT) was used to investigate the effects of sounds produced by impulsive pile driving on two size groups of hybrid striped bass (white bass Morone chrysops x striped bass Morone saxatilis ). The larger striped bass (mean size 17.2 g) had more severe injuries, as well as more total injuries, than the smaller fish (mean size 1.3 g). However, fish in each size group recovered from most injuries within 10 days of exposure. A comparison with different species from previously published studies show that current results support the observation that fishes with physoclistous swim bladders are more susceptible to injury from impulsive pile driving than are fishes with physostomous swim bladders.

To address growing concern over the impact of anthropogenic sound on fishes, a series of experiments was conducted that exposed several fish species to high-intensity low-frequency naval sonar. This study extends auditory findings by adding largemouth bass, yellow perch, and channel catfish. No effects on hearing were found in largemouth bass and yellow perch and only small effects in channel catfish (a fish with morphological adaptations for enhanced pressure reception). Together with prior findings, these results suggest limited impact on hearing from high-intensity sonar. Susceptibility may be due to genetic stock, developmental conditions, seasonal variation, and/or buoyancy during exposure.

Impulsive pile driving sound can cause injury to fishes, but no studies to date have examined whether such injuries include damage to sensory hair cells in the ear. Possible effects on hair cells were tested using a specially designed wave tube to expose two species, hybrid striped bass (white bass Morone chrysops × striped bass Morone saxatilis) and Mozambique tilapia (Oreochromis mossambicus), to pile driving sounds. Fish were exposed to 960 pile driving strikes at one of three treatment levels: 216, 213, or 210 dB re 1 μPa2·s cumulative Sound Exposure Level. Both hybrid striped bass and tilapia exhibited barotraumas such as swim bladder ruptures, herniations, and hematomas to several organs. Hybrid striped bass exposed to the highest sound level had significant numbers of damaged hair cells, while no damage was found when fish were exposed at lower sound levels. Considerable hair cell damage was found in only one out of 11 tilapia specimens exposed at the highest sound level. Results suggest that impulsive sounds such as from pile driving may have a more significant effect on the swim bladders and surrounding organs than on the inner ears of fishes, at least at the sound exposure levels used in this study.

Elasmobranch fishes have been around for hundreds of millions of years with very little evolutionary changes, yet our understanding of their hearing abilities is limited to only a few of the hundreds of extant species. Our general understanding suggests a relatively narrow hearing range with relatively poor sensitivity, particularly compared with many teleosts. This lack of knowledge makes it difficult to evaluate the potential effects that could be associated with exposure to anthropogenic noise. However, given the combination of the worldwide increase in anthropogenic aquatic noise as well as the drastic population decline in many species of elasmobranch fishes, it is imperative that noise-exposure studies be conducted to determine whether these fishes are being further threatened by our noise pollution.

Juvenile Chinook salmon, Oncorhynchus tshawytscha, were exposed to simulated high intensity pile driving signals to evaluate their ability to recover from barotrauma injuries. Fish were exposed to one of two cumulative sound exposure levels for 960 pile strikes (217 or 210 dB re 1 µPa(2)·s SEL(cum); single strike sound exposure levels of 187 or 180 dB re 1 µPa(2)⋅s SEL(ss) respectively). This was followed by an immediate assessment of injuries, or assessment 2, 5, or 10 days post-exposure. There were no observed mortalities from the pile driving sound exposure. Fish exposed to 217 dB re 1 µPa(2)·s SEL(cum) displayed evidence of healing from injuries as post-exposure time increased. Fish exposed to 210 dB re 1 µPa(2)·s SEL(cum) sustained minimal injuries that were not significantly different from control fish at days 0, 2, and 10. The exposure to 210 dB re 1 µPa(2)·s SEL(cum) replicated the findings in a previous study that defined this level as the threshold for onset of injury. Furthermore, these data support the hypothesis that one or two Mild injuries resulting from pile driving exposure are unlikely to affect the survival of the exposed animals, at least in a laboratory environment.

This study investigated immediate effects of intense sound exposure associated with low-frequency (170-320 Hz) or with mid-frequency (2.8-3.8 kHz) sonars on caged rainbow trout Oncorhynchus mykiss, channel catfish Ictalurus punctatus and hybrid sunfish Lepomis sp. in Seneca Lake, New York, U.S.A. This study focused on potential effects on inner ear tissues using scanning electron microscopy and on non-auditory tissues using gross and histopathology. Fishes were exposed to low-frequency sounds for 324 or 628 s with a received peak signal level of 193 dB re 1 microPa (root mean square, rms) or to mid-frequency sounds for 15 s with a received peak signal level of 210 dB re 1 microPa (rms). Although a variety of clinical observations from various tissues and organ systems were described, no exposure-related pathologies were observed. This study represents the first investigation of the effects of high-intensity sonar on fish tissues in vivo. Data from this study indicate that exposure to low and midfrequency sonars, as described in this report, might not have acute effects on fish tissues.

The response latencies of sensory neurons typically shorten with increases in stimulus intensity. In the central auditory system this phenomenon should have a significant impact on a number of auditory functions that depend critically on an integration of precisely timed neural inputs. Evidence from previous studies suggests that the auditory system not only copes with the potential problems associated with intensity-dependent latency change, but that it also modifies latency change to shape the response properties of many cells for specific functions. This observation suggests that intensity-dependent latency change may undergo functional transformations along the auditory neuraxis. The goal of our study was to explore these transformations by making a direct, quantitative comparison of intensity-dependent latency change among a number of auditory centers from the lower brainstem to the thalamus. We found two main ways in which intensity-dependent latency change transformed along the neuraxis: (1) the range of latency change increased substantially and (2) one particular type of latency change, which has been suggested to be associated with sensitivity to temporally segregated stimulus components, occurred only at the highest centers tested, the midbrain and thalamus. Additional testing in the midbrain (inferior colliculus) indicated that inhibitory inputs are involved in shaping latency change. Our findings demonstrate that the central auditory system modifies intensity-dependent latency changes. We suggest that these changes may be functionally incorporated, actively enhanced, or modified to suit specific functions of the auditory system.

The risk of effects to fishes and other aquatic life from impulsive sound produced by activities such as pile driving and seismic exploration is increasing throughout the world, particularly with the increased exploitation of oceans for energy production. At the same time, there are few data that provide insight into the effects of these sounds on fishes. The goal of this study was to provide quantitative data to define the levels of impulsive sound that could result in the onset of barotrauma to fish. A High Intensity Controlled Impedance Fluid filled wave Tube was developed that enabled laboratory simulation of high-energy impulsive sound that were characteristic of aquatic far-field, plane-wave acoustic conditions. The sounds used were based upon the impulsive sounds generated by an impact hammer striking a steel shell pile. Neutrally buoyant juvenile Chinook salmon (Oncorhynchus tshawytscha) were exposed to impulsive sounds and subsequently evaluated for barotrauma injuries. Observed injuries ranged from mild hematomas at the lowest sound exposure levels to organ hemorrhage at the highest sound exposure levels. Frequency of observed injuries were used to compute a biological response weighted index (RWI) to evaluate the physiological impact of injuries at the different exposure levels. As single strike and cumulative sound exposure levels (SEL(ss), SEL(cum) respectively) increased, RWI values increased. Based on the results, tissue damage associated with adverse physiological costs occurred when the RWI was greater than 2. In terms of sound exposure levels a RWI of 2 was achieved for 1920 strikes by 177 dB re 1 µPa(2)⋅s SEL(ss) yielding a SEL(cum) of 210 dB re 1 µPa(2)⋅s, and for 960 strikes by 180 dB re 1 µPa(2)⋅s SEL(ss) yielding a SEL(cum) of 210 dB re 1 µPa(2)⋅s. These metrics define thresholds for onset of injury in juvenile Chinook salmon.