Single-strike Sound Exposure Levels Research Articles

Underwater sound characteristics from down-the-hole pile drilling for a coastal construction activity

Sound generated by pile installation using a down-the-hole (DTH) hammer is not well documented and differs in character from sound generated using conventional impact or vibratory hammers. This study describes underwater acoustic characteristics from DTH pile drilling during the installation of 0.84-m shafts within 1.22-m steel piles associated with a cruise ship terminal construction in Ward Cove, Alaska. The median single-strike sound exposure levels measured at 10 m were 138 and 142 dB re 1 μPa2s for each of the two piles, with cumulative sound exposure levels of 188 and 193 dB re 1 μPa2s at 10 m, respectively. The sound levels measured in this study were significantly lower than previous measurements of DTH pile driving, and the sound is determined to be less impulsive in this study as compared previous studies. These differences likely result from fact that the DTH hammer used at Wade Cove did not make direct contact with the pile, as had been the case in previous studies. Further research is needed to investigate DTH piling techniques and associated sound-generating mechanisms and to differentiate the various impulsive structures from anthropogenic underwater noise in general.

Behavioral Responses of a Harbor Porpoise (Phocoena phocoena) Depend on the Frequency Content of Pile-Driving Sounds

The loud, impulsive, broadband underwater sounds produced during offshore pile driving are known to have auditory and behavioral effects on harbor porpoises (Phocoena phocoena) in the areas around piling sites. Thresholds to prevent behavioral effects have not yet been set, and it is unclear whether or not auditory frequency weighting of piling sounds, as used for criteria to protect hearing (Southall et al., 2019), is also useful for predicting behavioral responses and therefore required to set safety criteria and develop mitigation measures. A harbor porpoise in a pool was exposed to playbacks of piling sounds, and her behavioral responses were quantified in comparison to baseline periods without piling sounds. The full-spectrum playback piling sound was recorded at 100 m from a piling site for an offshore wind turbine. For comparison, five low-pass filtered (6.3, 3.2, 1.5, 1.0, and 0.5 kHz) versions of the sound in which the bandwidth decreased were played back at the same duty cycle (46 strikes/min) and similar single-strike sound exposure levels (power average in the pool: 135 dB re 1 µPa²s; t90: 90 to 100 ms). As the bandwidth of the piling sounds decreased, the porpoise’s behavioral response became weaker. Although these results are based on only one porpoise, they indicate that harbor porpoises respond most strongly to the higher frequencies in piling sounds. Therefore, frequency weighting of the sound exposure level (SEL) will improve prediction of behavioral responses, and behavioral response threshold levels for criteria should also be expressed as weighted SELs. However, it is unclear whether the weighting for predicting auditory effects is also the best weighting to predict behavioral effects. Mitigation of the effects of piling sounds on harbor porpoise behavior should be focused on reducing the high-frequency part of the spectrum.

Acoustic characteristics from an in-water down-the-hole pile drilling activity.

Sound generated by pile installation using a down-the-hole (DTH) hammer is not well documented and differs in character from sound generated by conventional impact and vibratory pile driving. This paper describes underwater acoustic characteristics from DTH pile drilling during the installation of 0.84-m shafts within 1.22-m steel piles in Ketchikan, Alaska. The median single-strike sound exposure levels were 138 and 142 dB re 1 μPa2s at 10 m for each of the two piles, with cumulative sound exposure levels of 185 and 193 dB re 1 μPa2s at 10 m, respectively. The sound levels measured at Ketchikan were significantly lower than previous studies, and the sound was determined to be non-impulsive in this study as compared to impulsive in previous studies. These differences likely result from the DTH hammer not making direct contact with the pile, as had been the case in previous studies. Therefore, we suggest using the term DTH pile drilling to distinguish from DTH pile driving when the hammer strikes the pile. Further research is needed to investigate DTH piling techniques and associated sound-generating mechanisms and to differentiate the various types of sound emitted, which has important implications for the underwater sound regulatory community.

Acoustic characteristics from an in-water down-the-hole pile drilling activity

Sound generated by pile installation using a down-the-hole (DTH) hammer is not well documented and differs in character from sound generated by conventional impact and vibratory pile driving. This paper describes underwater acoustic characteristics from DTH pile drilling during the installation of 0.84-m shafts within 1.22-m steel piles in Ketchikan, Alaska. The median single-strike sound exposure levels measured at 10 m were 138 and 142 dB re 1 μPa2 s for each of the two piles, with cumulative sound exposure levels of 188 and 193 dB re 1 μPa2 s at 10 m, respectively. The sound levels measured at Ketchikan were significantly lower than previous studies, and the sound is determined to be non-impulsive in this study as compared to impulsive in the previous studies. These differences likely result from fact that the DTH hammer used at Ketchikan did not make direct contact with the pile, as had been the case in previous studies. Further research is needed to investigate DTH piling techniques and associated sound-generating mechanisms, and to differentiate the various types of sound emitted.

Underwater noise characterization of down-the-hole pile driving activities off Biorka Island, Alaska

Although down-the-hole (DTH) pile driving is increasingly used for in-water pile installation, the characteristics of underwater noise from DTH pile driving is largely undocumented and unstudied. This study presents a comprehensive analysis of the noise characteristics during DTH pile driving of two steel pipe piles in shallow waters off southeast Alaska. The results showed that single-strike sound exposure levels measured at 10 m were 147 and 145 dB re 1 μPa2s with a total of 21,742 and 38,631 hammer strikes, with cumulative sound exposure levels to install each pile at 192 and 191 dB re 1 μPa2s, respectively. Though noise levels from a single strike was lower than impact pile driving of a similar pile, the cumulative sound exposure levels are likely comparable due to the much higher striking rate.

Estimating the effects of pile driving sounds on seals: Pitfalls and possibilities.

Understanding the potential effects of pile driving sounds on marine wildlife is essential for regulating offshore wind developments. Here, tracking data from 24 harbour seals were used to quantify effects and investigate sensitivity to the methods used to predict these. The Aquarius pile driving model was used to model source characteristics and acoustic propagation loss (16 Hz-20 kHz). Predicted cumulative sound exposure levels (SELcums) experienced by each seal were compared to different auditory weighting functions and damage thresholds to estimate temporary (TTS) and permanent (PTS) threshold shift occurrence. Each approach produced markedly different results; however, the most recent criteria established by Southall et al. [(2019) Aquat. Mamm. 45, 125-232] suggests that TTS occurrence was low (17% of seals). Predictions of seal density during pile driving made by Russell et al. [(2016) J. Appl. Ecol. 53, 1642-1652] were compared to distance from the wind farm and predicted single-strike sound exposure levels (SELss) by multiple approaches. Predicted seal density significantly decreased within 25 km or above SELss (averaged across depths and pile installations) of 145 dB re 1 μPa2⋅s. However, there was substantial variation in SELss with depth and installation, and thus in the predicted relationship with seal density. These results highlight uncertainty in estimated effects, which should be considered in future assessments.

Effects of multiple exposures to pile driving noise on harbor porpoise hearing during simulated flights—An evaluation tool

Exploitation of renewable energy from offshore wind farms is substantially increasing worldwide. The majority of wind turbines are bottom mounted, causing high levels of impulsive noise during construction. To prevent temporary threshold shifts (TTS) in harbor porpoise hearing, single strike sound exposure levels (SELSS) are restricted in Germany by law to a maximum of 160 dB re 1 μPa2s at a distance of 750 m from the sound source. Underwater recordings of pile driving strikes, recorded during the construction of an offshore wind farm in the German North Sea, were analyzed. Using a simulation approach, it was tested whether a TTS can still be induced under current protective regulations by multiple exposures. The evaluation tool presented here can be easily adjusted for different sound propagation, acoustic signals, or species and enables one to calculate a minimum deterrence distance. Based on this simulation approach, only the combination of SELSS regulation, previous deterrence, and soft start allow harbor porpoises to avoid a TTS from multiple exposures. However, deterrence efficiency has to be monitored.

Effect of Pile-Driving Playback Sound Level on Fish-Catching Efficiency in Harbor Porpoises (Phocoena phocoena)

The foundations of offshore wind turbine parks are often constructed by means of percussion pile driving. Broadband impulsive sounds generated by pile driving may disturb and distract marine mammals such as harbor porpoises (Phocoena phocoena); their concentration may be reduced, affecting the skills they need for foraging (e.g., timing and precision) or reducing their ability to catch prey and, thus, their foraging efficiency. The resulting reduction in fitness may eventually lead to population declines. Therefore, it is important to understand the effects of these anthropogenic sounds on the ability of harbor porpoises to catch fish. Two captive harbor porpoises (porpoise F05 and porpoise M06) performed a fish-catching task (i.e., retrieving dead fish from a net feeding cage) while they were exposed to low ambient noise (quiet conditions) and impulsive pile-driving playback sounds at three (porpoise M06) or four (porpoise F05) mean received single-strike sound exposure levels (SELss) between 125 and 143 dB re 1 µPa2s. The two study animals differed in their fish-catching success rate at all noise levels, including under quiet conditions: Porpoise F05 was less likely to catch fish than porpoise M06. They also responded differently to increasing SELss: Only porpoise F05 was significantly more likely to terminate trials and less likely to catch fish as SELss increased above 134 dB, but her trial failure rate remained unaffected by increasing SELss. The time taken to catch a fish did not vary with SELss but was slightly longer for porpoise F05 than for porpoise M06. Results suggest that high-amplitude pile driving sounds are likely to negatively affect foraging in some harbor porpoises by decreasing their catch success rate and increasing the termination rate of their fish-catching attempts; the severity of the effects is likely to increase with increasing pile driving SELss. However, individual differences in responses to sound, termination rates, and fish-catching success (even in ambient conditions) may complicate the quantification of the impacts of pile driving sounds on harbor porpoises.

Acoustic dose-behavioral response relationship in sea bass (Dicentrarchus labrax) exposed to playbacks of pile driving sounds

The foundations of offshore wind turbines are attached to the sea bed by percussion pile driving. Pile driving sounds may affect the behavior of fish. Acoustic dose-behavioral response relationships were determined for sea bass in a pool exposed for 20 min to pile driving sounds at seven mean received root-mean-square sound pressure levels [SPLrms; range: 130–166 dB re 1 μPa; single strike sound exposure level (SELss) range: 122–158; 6 dB steps]. Initial responses (sudden, short-lived changes in swimming speed and direction) and sustained responses (changes in school cohesion, swimming depth, and speed) were quantified. The 50% initial response threshold occurred at an SELss of 131 dB re 1 μPa2 s for 31 cm fish and 141 dB re 1 μPa2 s for 44 cm fish; the small fish thus reacted to lower SELss than the large fish. Analysis showed that there is no evidence, even at the highest sound level, for any consistent sustained response to sound exposure by the study animals. If wild sea bass are exposed to pile driving sounds at the levels used in the present study, there are unlikely to be any adverse effects on their ecology, because the initial responses after the onset of the piling sound observed in this study were short-lived.

Comprehensive summary of the impulsive pile driving sound exposure study series

The high intensity controlled impedance fluid filled wave tube (HICI-FT) was used to expose fishes, in the laboratory, to impulsive sound signals under controlled conditions. Fish species were exposed to pile driving signals under different experimental paradigms, followed by detailed investigations of their physiological tissue response (aka, barotrauma injuries). Most often the cumulative sound exposure level (SELcum) was held constant while varying the number of pile strikes and the single strike sound exposure level (SELss). Altering these three variables proved the equal energy hypothesis irrelevant; the higher SELss values with fewer number of strikes caused a highest injury levels. The first dose-response curve was generated for fish responses. Comparisons between different species showed fish with no swim bladder at low injury risk, fish with a closed swim bladder (physoclists) at a high injury risk, and fish with an open swim bladder (physostomes) at a moderate injury risk. If fish find safe haven in the wild, they have potential to heal within 10 days of receiving moderate injuries. Tissue injury appears to occur before damage to hair cells occurs. And most recently, fish show injury after exposure to as few as 8-impulsive signals that have a high SELss value.

Passive Acoustic Observations in the Shallow Waters of Northwest Bay of Bengal to Study the Effects of Impact Pile Driving on Fish Chorus

AbstractAmbient noise time series measurements were recorded in the shallow water of Northwest Bay of Bengal. A few data sets revealed the presence of impact pile-driving noise. The site is also known for the presence of the speciesTerapon theraps(Family:Terapontidae), and the fish chorus was recorded during the measurement period. Sound metrics of impact pile-driving noise were calculated to assess their potential impacts on fish chorus. Averaged peak sound pressure level reached 162 dB re 1 μPa, and single-strike sound exposure level is about 134 dB re 1 μPa2s, leading to a cumulative sound exposure level of approximately 148 dB re 1 μPa2s. The impact pile-driving signal has the highest energy in lower frequency band over 0.05‐1 kHz. It is observed thatT. therapsfish chorus also displays their pulse repetition rate and swimbladder spectral peaks at lower frequencies. Detailed analysis of the entire data sets indicates that the fishes were exposed to the pile-driving noise, which would have an impact on the chorus made by them.

Effects of pile driving on fishes

We examined the physiological effects of impact pile driving on fishes using a specially designed tube that allows replication of the far field acoustic conditions of impulsive stimuli. Studies show that the received signal levels needed to result in onset of effects is a combination of single strike sound exposure level (SELss) and cumulative sound exposure level (SELcum), although not in an equal energy relationship. In contrast to current interim regulations, which indicate that the onset of physiological effects occurs at 187 dB SELcum, our experimental results for six species of fishes showed that the onset of physiological effects, none of which produced mortality, was at about 207 dB SELcum. This onset SELcum had to be at least 7–10 dB higher to result in effects that could potentially be mortal. Additional studies showed that fishes can recover from the effects of pile driving and that a fish species without a swim bladder showed no effects, at least up to an SELcum of 216 dB. Investigations on the effects of pile driving on sensory hair cells of the inner ear, an analog for hearing loss, showed that damage only occurred at SELcum that are substantially higher than onset of other effects.

Effects of exposure to pile-driving sounds on the lake sturgeon, Nile tilapia and hogchoker

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.

Recovery of Barotrauma Injuries in Chinook Salmon, Oncorhynchus tshawytscha from Exposure to Pile Driving Sound

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 µPa2·s SELcum; single strike sound exposure levels of 187 or 180 dB re 1 µPa2⋅s SELss 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 µPa2·s SELcum displayed evidence of healing from injuries as post-exposure time increased. Fish exposed to 210 dB re 1 µPa2·s SELcum sustained minimal injuries that were not significantly different from control fish at days 0, 2, and 10. The exposure to 210 dB re 1 µPa2·s SELcum 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.