Transmission loss patterns from acoustic harassment and deterrent devices do not always follow geometrical spreading predictions

Acoustic harassment and deterrent devices have become increasingly popular mitigation tools for negotiating the impacts of marine mammals on fisheries. The rationale for their variable effectiveness remains unexplained, but high variability in the surrounding acoustic field may be relevant. In the present study, the sound fields of one acoustic harassment device and three acoustic deterrent devices were measured at three study sites along the Scandinavian coast. Superimposed onto an overall trend of decreasing sound exposure levels with increasing range were large local variations in the sound level for all sources in each of the environments. This variability was likely caused by source directionality, inter-ping source level variation and multipath interference. Rapid and unpredictable variations in the sound level as a function of range deviated from expectations derived from spherical and cylindrical spreading models and conflicted with the classic concept of concentric zones of increasing disturbance with decreasing range. Under such conditions, animals may encounter difficulties when trying to determine the direction to and location of a sound source, which may complicate or jeopardize avoidance responses.     

Involvement of the mechanosensory complex structures of the cricket <Emphasis Type="Italic">Phaeophilacris bredoides</Emphasis> in triggering of motor responses to sound

Using an ethological approach, we studied the possibility of sound perception as well as probable contribution of diverse mechanosensory systems composing the mechanosensory complex to triggering of motor responses to sound stimulation in imaginal crickets Phaeophilacris bredoides lacking the tympanal organs (“deaf”). It was shown that Ph. bredoides imagoes are able to perceive sounds and respond to sound cues by a locomotor reaction in a relatively broad frequency range which becomes narrower as sound intensity decreases [0.1–6.0 kHz (111 ± 3 dB SPL), 0.1–1.5 kHz (101 ± 3 dB SPL), 0.1–1.3 kHz (91 ± 3 dB SPL), 0.1–0.6 kHz (81 ± 3 dB SPL), and 0.1 kHz (71 ± 3 dB SPL)]. Sound perception and triggering ofmotor responses appear to involve the cercal organs (CO), subgenual organs (SO) and, probably, other distant mechanosensory organs (DMO). CO are essential for triggering of locomotor responses to sound within the ranges of 1.6–6.0 kHz (111 ± 3 dB SPL), 1–1.5 kHz (101 ± 3 dB SPL), 0.9–1.3 kHz (91 ± 3 dB SPL), and 0.5–0.6 kHz (81 ± 3 dB SPL). SO and, probably, other DMO provide locomotor responses to sound within the ranges of 0.1–6.0 kHz (111 ± 3 dB SPL), 0.1–0.8 kHz (101 ± 3 dB SPL), 0.1–0.4 kHz (91 ± 3 dB SPL), and 0.1–0.4 kHz (81 ± 3 dB SPL). From this, it follows that “deaf” (nonsinging) Ph. bredoides can perceive sounds using CO, SO and, probably, other DMO, which (as in singing crickets) are likely to compose an integrated mechanosensory complex providing adequate acoustic behavior of this cricket species. Performance efficiency and sensitivity of the mechanosensory complex (specifically, of CO) rely on the thoroughness of grooming. Following self-cleaning of CO, the level of cricket motor activity in response to cue presentation returned to the baseline and sometimes even increased. Whether or not crickets of this species communicate acoustically is yet to be found out, however, we suggest that the mechanosensory complex, which triggers motor responses to a sound, is normally involved in the defensive escape response aimed at rescuing from predators.     

A Cervid Vocal Fold Model Suggests Greater Glottal Efficiency in Calling at High Frequencies

Male Rocky Mountain elk (Cervus elaphus nelsoni) produce loud and high fundamental frequency bugles during the mating season, in contrast to the male European Red Deer (Cervus elaphus scoticus) who produces loud and low fundamental frequency roaring calls. A critical step in understanding vocal communication is to relate sound complexity to anatomy and physiology in a causal manner. Experimentation at the sound source, often difficult in vivo in mammals, is simulated here by a finite element model of the larynx and a wave propagation model of the vocal tract, both based on the morphology and biomechanics of the elk. The model can produce a wide range of fundamental frequencies. Low fundamental frequencies require low vocal fold strain, but large lung pressure and large glottal flow if sound intensity level is to exceed 70 dB at 10 m distance. A high-frequency bugle requires both large muscular effort (to strain the vocal ligament) and high lung pressure (to overcome phonation threshold pressure), but at least 10 dB more intensity level can be achieved. Glottal efficiency, the ration of radiated sound power to aerodynamic power at the glottis, is higher in elk, suggesting an advantage of high-pitched signaling. This advantage is based on two aspects; first, the lower airflow required for aerodynamic power and, second, an acoustic radiation advantage at higher frequencies. Both signal types are used by the respective males during the mating season and probably serve as honest signals. The two signal types relate differently to physical qualities of the sender. The low-frequency sound (Red Deer call) relates to overall body size via a strong relationship between acoustic parameters and the size of vocal organs and body size. The high-frequency bugle may signal muscular strength and endurance, via a ‘vocalizing at the edge’ mechanism, for which efficiency is critical.     

Involvement of Mechanosensory Complex Structures of the Cricket <Emphasis Type="Italic">Gryllus bimaculatus</Emphasis> Larvae (Orthoptera,Gryllidae) in Triggering of Motor Responses to Sound

Using an ethological approach, we studied the possibility of sound perception as well as probable contribution of diverse mechanosensory systems composing the mechanosensory complex to triggering of motor responses to sound stimulation in the cricket Gryllus bimaculatus larvae. It was shown that larvae can perceive sounds and respond to them by a locomotor reaction in a relatively broad frequency range, which becomes narrower as sound intensity decreases [0.1–6.6 kHz (111 ± 3 dB SPL), 0.1–1.4 kHz (101 ± 3 dB SPL), 0.1–0.8 kHz (91 ± 3 dB SPL]. Sound perception and triggering of motor responses appear to involve the cercal organs (CO), subgenual organs (SO) and, probably, other distant mechanosensory organs (DMO). Normal functioning of CO is essential for triggering locomotor responses to sound within the ranges of 1–1.4 kHz (101 ± 3 dB SPL) and 0.1–0.8 kHz (91 ± 3 dB SPL). CO are not necessary for triggering of motor responses to cues with an intensity of 111 ± 3 dB. SO and, probably, other DMO provide locomotor responses to sound within the ranges of 0.1–6.6 kHz (111 ± 3 dB SPL), 0.1–0.9 kHz (101 ± 3 dB SPL), and 0.1–0.3 kHz (91 ± 3 dB SPL). Thus, last instar larvae of G. bimaculatus lacking the tympanal organs can perceive sounds using CO, SO and, probably, other DMO, which (as in cricket imagoes) are likely to compose an integrated mechanosensory complex providing adequate acoustic behavior of this cricket species. Performance efficiency and sensitivity of the mechanosensory complex (specifically, CO) rely on the thoroughness of grooming. After self-cleaning of CO, the level of larval motor activity in response to cue presentation returned to the baseline and sometimes even increased. We assume that under normal conditions the mechanosensory complex, which triggers motor responses to a sound, is involved in the defensive escape response aimed at rescuing from predators.     

Severe constraints for sound communication in a frog from the South American temperate forest

The efficiency of acoustic communication depends on the power generated by the sound source, the quality of the environment across which signals propagate, the environmental noise and the sensitivity of the intended receivers. Eupsophus calcaratus, an anuran from the temperate austral forest, communicates by means of an advertisement call of weak intensity in a sound-attenuating environment. To estimate the range over which these frogs communicate effectively, we conducted measurements of sound level and degradation patterns of propagating advertisement calls in the field, and measurements of auditory thresholds to pure tones and to natural calls in laboratory conditions. The results show that E. calcaratus produces weak advertisement calls of about 72 dB sound pressure level (SPL) at 0.25 m from the caller. The signals are affected by attenuation and degradation patterns as they propagate in their native environment, reaching average values of 61 and 51 dB SPL at 1 and 2 m from the sound source, respectively. Midbrain multi-unit recordings show a relatively low auditory sensitivity, with thresholds of about 58 dB SPL for conspecific calls, which are likely to restrict communication to distances shorter than 2 m, a remarkably short range as compared to other anurans.     

Spatial orientation in the bushcricket <Emphasis Type="Italic">Leptophyes punctatissima</Emphasis> (Phaneropterinae; Orthoptera): III. Peripheral directionality and central nervous processing of spatial cues

We examined peripheral and central nervous cues underlying the ability of the bushcricket Leptophyes punctatissima to orient to elevated and depressed sound sources broadcasting the female acoustic reply. The peripheral spatial directionality of the ear was measured physiologically using monaural preparations of an auditory interneuron (T-fibre). In the azimuth, maximal interaural intensity differences of 18 dB occur between ipsi- and contralateral stimulation. With increasing elevation or depression of the sound sources, IIDs decrease systematically and reach zero with the source exactly above or below the preparation. Bilateral, simultaneous recordings of the activity of the pair of interneurons allowed determining the binaural discharge differences which occur in response to the extremely short (1 ms) female reply. These discharge differences are large (four action potentials/stimulus) and reliable in the azimuth with lateral stimulation, and decrease gradually with more frontal stimulation. With elevation and depression of sound sources these differences again decrease to one action potential/stimulus at 60° or 75° elevation, and lateral stimulus angles of about 60°. We also calculated the reliability with which a receiver could correctly determine the location of the sound source. We discuss these quantitative measures in relation to the spatial phonotactic behaviour of male L. punctatissima.     

Ample active acoustic space of a frog from the South American temperate forest

The efficiency of acoustic communication depends on the power generated by the sound source, the attributes of the environment across which signals propagate, the environmental noise and the sensitivity of the intended receivers. Eupsophus emiliopugini, an anuran from the temperate austral forest communicates by means of an advertisement call of moderate intensity within the range for anurans. To estimate the range over which these frogs communicate effectively, we conducted measurements of call sound levels and of auditory thresholds to pure tones and to synthetic conspecific calls. The results show that E. emiliopugini produces advertisement calls of about 84 dB SPL at 0.25 m from the caller. The signals are affected by attenuation as they propagate, reaching average values of about 47 dB SPL at 8 m from the sound source. Midbrain multi-unit recordings show quite sensitive audiograms within the anuran range, with thresholds of about 44 dB SPL for synthetic imitations of conspecific calls, which would allow communication at distances beyond 8 m. This is an extended range as compared to E. calcaratus, a related syntopic species for which a previous study has shown to be restricted to active acoustic spaces shorter than 2 m. The comparison reveals divergent strategies for related taxa communicating amid the same environment.     

Sound localization by the Hawaiian squirrelfishes, Myripristis berndti and M. argyromus

Sound localization was investigated in a large pond open to a bay and similar to the normal environment of the animals. Observations were made of fish movements towards one of two underwater loud-speakers emitting squirrelfish alarm calls normally produced in response to predators. When the sound source was within 2·0 m of the test cage housing the fish, the subjects faced and moved toward the speaker. The animals responded some of the time when the source was within 3·0 m but generally did not orient to the sound source when the speaker was beyond 3·0 m. Response loss was correlated with the fish being in the acoustic far-field. Possible cues which release and direct localization remain unknown, but include particle velocity information alone, or some change in particle velocity: pressure relationships.     

Synthetic communication signals influence wild harbour porpoise (Phocoena phocoena) behaviour

We used our novel and programmable Porpoise Alarm (PAL, patd.) to synthesize life-like, electronic harbour porpoise communication signals based on those described for captive animals. In the Little Belt, Denmark, we employed PAL (source level 158 ± 1 dB p–p re 1 μPa@1 m; centroid frequency 133 ± 8.5 kHz) to synthesize three aggressive click train types termed “A”, “F3” and “M1” to naive, free-living harbour porpoises. Via theodolite tracking (372 h of total visual effort spread over 10 expeditions) we found that, depending on signal type, porpoises either avoid or become attracted to PAL: Signal types “A” and “F3” are slight deterrents, porpoises increasing minimum range (+23 to 32 m, respectively), whereas “M1” attracts porpoises, reducing range (by ? 29 m). As determined via archival acoustic detectors (AADs), both signals “F3” and “M1” led the animals to significantly intensify their click rate (by +10% and 68%, respectively) while signal “A” led to a significant reduction ( ? 59%). We propose that equipping fishing gear with PAL emitting signal “F3” could potentially reduce porpoise by-catch by increasing (1) awareness through enhanced echolocation and (2) distance to the nets. Detection probability and radius of PAL/AAD tandems could be improved by emitting signal “M1” to focus porpoise echolocation signals on the AAD. The signal may also be useful in luring animals away from hazards, which may be helpful for conservation measures prior to the onset of harmful acoustic activities such as pile-driving, seismic exploration or ammunition clearance.     

REACTION OF FIN WHALES BALAENOPTERA PHYSALUS TO AN EARTHQUAKE

ABSTRACT

Whales living within seismically active regions are subject to intense disturbances from strong sounds produced by earthquakes that can kill or injure individuals. Nishimura & Clark (1993) relate the possible effects of underwater earthquake noise levels in marine mammals, adducing that T-phase source signal level (10- to 30- Hz range) can exceed 200 dB re: 1 μPa at 1 m, for a magnitude 4–5 earthquake, sounds audible to fin whales which produce low frequency sounds of 16–20/25–44 Hz over 0.5–1s, typically of 183 dB re: 1 μPa at 1 m. Here we present the response of a fin whale to a 5.5 Richter scale earthquake that took place on 22 February 2005, in the Gulf of California. The whale covered 13 km in 26 min (mean speed = 30.2 km/h). We deduce that the sound heard by this whale might have triggered the costly energy expenditure of high speed swimming as a seismic-escape response. These observations support the hypothesis of Richardson et al. (1995) that cetaceans may flee from loud sounds before they are injured, when exposed to noise in excess of 140 dB re: 1 μPa 1 m.     

Localizing wild chimpanzees with passive acoustics

1. Localizing wildlife contributes in multiple ways to species conservation. Data on animal locations can reveal elements of social behavior, habitat use, population dynamics, and be useful in calculating population density. Acoustic localization systems (ALS) are a non‐invasive method widely used in the marine sciences but not well established and rarely employed for terrestrial species.
2. We deployed an acoustic array in a mountainous environment with heterogeneous vegetation, comprised of four custom‐built GPS synchronized acoustic sensors at about 500 m intervals in Issa Valley, western Tanzania, covering an area of nearly 2 km². Our goal was to assess the precision and error of the estimated locations by conducting playback tests, but also by comparing the estimated locations of wild chimpanzee calls with their true locations obtained in parallel during follows of individual chimpanzees. We assessed the factors influencing localization error, such as wind speed and temperature, which fluctuate during the day and are known to affect sound transmission.
3. We localized 282 playback sounds and found that the mean localization error was 27 ± 21.8 m. Localization was less prone to error and more precise during early mornings (6:30 h) compared to other periods. We further localized 22 wild chimpanzee loud calls within 52 m of the location of a researcher closely following the calling individuals.
4. We demonstrate that acoustic localization is a powerful tool for chimpanzee monitoring, with multiple behavioral and conservation applications. Its applicability in studying social dynamics and revealing density estimation among many others, especially but not exclusively for loud calling species, provides an efficient way of monitoring populations and informing conservation plans to mediate species loss.

     

The audibility of frog choruses to migrating birds

Breeding choruses of Hyla crucifer and H. versicolor are loud enough to be audible to migrating birds up to at least 1 km from their source, both vertically and horizontally, provided that no large obstacles intervene. During May in south-eastern New York State sound pressure levels (A weighting) at altitudes of 200 to 965 m and slant ranges from the frogs of 225 to 1020 m varied from 28 to 52 dB SPL.     

螽斯(Deracantha onos)的趋声性与定位精度

本文研究雌硕螽(Deracantha onos)对正在鸣叫的同种雄螽斯的趋声运动的特征,并依据其行走路径测算出定位精度。只有同种雄螽斯的叫声才能诱发雌螽斯作趋声反应。雌螽斯趋声运动的速度约比非趋声行走高十倍。趋声路径呈“之”字形。用极性方位图表示螽斯趋声运动的方向性。有叫声时,相对于声源为零度的方向上的权最大,介于0.34与0.69之间。极性方位图的质心的方位角代表声定位的精度,小于3°。趋声路径的平均方位角为0.4°,标准离差10°左右。     

Sounds audible to migrating birds

We have measured sound levels from frog choruses in eastern New York State at altitudes of up to several hundred metres. Rana pipiens choruses from small ponds often could be recorded by a radio microphone up to 500 m, and on an especially favourable night with light winds they were clearly audible even at 965 m at about 20 dB SPL in the 1·5 to 2·5 2·5 kHz frequency band. Sound travels upward much farther and more predictably than along the surface. Many natural sounds, including those from frogs, insects, whitecaps, and perhaps wind-blown vegetation, arise from large areas and therefore act as extended sources. The intensities of such sounds decrease with altitude more slowly than expected from the inverse square law. Natural sound fields provide migrating birds with a potential source of information about the kind of land or water below them, and their progress over acoustic landmarks could inform them about wind velocity. Because atmospheric absorption increases with frequency, several hundred metres of air act as a low-pass filter, so that altitude could be estimated from the relative reduction of higher frequencies in a familiar sound.     

Temporal and Spatial Comparisons of Underwater Sound Signatures of Different Reef Habitats in Moorea Island,French Polynesia

As environmental sounds are used by larval fish and crustaceans to locate and orientate towards habitat during settlement, variations in the acoustic signature produced by habitats could provide valuable information about habitat quality, helping larvae to differentiate between potential settlement sites. However, very little is known about how acoustic signatures differ between proximate habitats. This study described within- and between-site differences in the sound spectra of five contiguous habitats at Moorea Island, French Polynesia: the inner reef crest, the barrier reef, the fringing reef, a pass and a coastal mangrove forest. Habitats with coral (inner, barrier and fringing reefs) were characterized by a similar sound spectrum with average intensities ranging from 70 to 78 dB re 1μPa.Hz^-1. The mangrove forest had a lower sound intensity of 70 dB re 1μPa.Hz^-1 while the pass was characterized by a higher sound level with an average intensity of 91 dB re 1μPa.Hz^-1. Habitats showed significantly different intensities for most frequencies, and a decreasing intensity gradient was observed from the reef to the shore. While habitats close to the shore showed no significant diel variation in sound intensities, sound levels increased at the pass during the night and barrier reef during the day. These two habitats also appeared to be louder in the North than in the West. These findings suggest that daily variations in sound intensity and across-reef sound gradients could be a valuable source of information for settling larvae. They also provide further evidence that closely related habitats, separated by less than 1 km, can differ significantly in their spectral composition and that these signatures might be typical and conserved along the coast of Moorea.     

The precedence effect for signals moving in the horizontal plane

The precedence effect refers to a group of auditory phenomena related to the ability to locate sound sources in reverberant environments. In the present study, this phenomenon was investigated using two moving signals. The first signal was direct (lead) and the other was delayed (lag). The motion of the sound source was created by successive switching of ten loudspeakers. The continuity of the motion was created by simultaneously attenuating the stimulus in the previous loudspeaker and enhancing it in the next one. The length of the path of the lead and lag was 34°. The lead moved from 34° to 0° (to the right) and the lag moved –52° to –86° (to the left). The duration of the lead and the lag was 1 s. Lead–lag delays ranged from 1 to 40 ms. Subjects had to indicate the location of the lag. The results indicate that the lead signal dominated in the sound localization at short delay durations (up to 18 ms). In spite of the instructions, all the subjects pointed at the lead, which suggests that they perceived the lag in this location. Two distinct sounds were perceived at the longest delays. The mean echo threshold and its standard deviation in eight subjects was 9.6 ± 4.5 ms.     

THE MEASUREMENT OF VOCAL AMPLITUDE AND VOCAL RADIATION PATTERN IN BLUE MONKEYS AND GREY-CHEEKED MANGABEYS

ABSTRACT

The substitution method was adopted from industrial acoustics (Francois and de Montussaint 1972) to “eliminate the influence of the environment” on measurements of the amplitude of vocalizations given by blue monkeysCercopithecus mitis and grey-cheeked mangabeysCercocebus albigena. Measurements were conducted of sound power and sound pressure level of representative utterances. Monkey vocal radiation patterns were also measured. The results showed that vocal amplitude ranged from 62 dB to 100 dB in sound pressure (re 1 pw). At a distance of 2 m, the loudest calls approached an amplitude of 110 dB SPL, a level about equal to the loudest human yell. The measurements of call amplitude conducted here exceeded those derived from the field by approximately 10 dB. It was shown that the discrepancy in amplitude between these laboratory based measurements and earlier measurements conducted under field conditions (Waser and Waser 1977) was probably due to destructive interference between the direct wave and the “ground wave”, a phase shifted wave reflected from the ground. Measurements of radiation patterns of primate vocalizations showed that, like human speech, directivity was a function of frequency, with high-frequency components being radiated more directionally than lower-frequency components. However, primate utterances were in general radiated more omnidirectionally than was human speech.     

URBAN NOISE PREDICTS SONG FREQUENCY IN NORTHERN CARDINALS AND AMERICAN ROBINS

ABSTRACT

We examined the extent to which acoustic noise in urban environments influences song characteristics and singing behaviour of Northern Cardinals Cardinalis cardinalis and American Robins Turdus migratorius. We predicted that, in response to loud noise, birds would improve signal transmission by (1) increasing singing rate and (2) adjusting song characteristics such as pitch and length. From May—July 2006, 42 cardinals and 53 robins were recorded in forests located within four acoustic environments in central Ohio: rural, residential, commercial, and highway. Following each recording, we measured ambient noise level and recorded information describing location, weather, habitat, and conspecific presence within 75 m. As predicted, frequency range was positively correlated with noise level for both species, but neither song length nor rate was related to noise level for either species. These data support the idea that anthropogenic noise influences avian singing behaviour and acts as a selective force in urban areas.     

Avoidance responses to low frequency sound in downstream migrating Atlantic salmon smolt, Salmo salar

The possibility of using intense sound as an acoustic barrier for downstream migrating smolt of the Atlantic salmon ( Salmo salar ) was studied by observing, the reactions of smolt to 10 and 150 Hz sounds in a small river. At the observation site the river branched into a main course and a minor channel, the latter rejoining the main stream after 30 m. The sound sources were positioned at the lower end of the channel. The number of smolt re-entering the mam stream at the lower end of the channel was recorded during alternating periods with and without sound. Intense 150 Hz sound had no observable effects on the smolt, even at intensities 114 dB above the hearing threshold at this frequency. At intensities above 1.0. 10⁻²ms⁻² the 10 Hz sound was an effective deterrent for the smolt, which turned and left the channel at the upstream branching point.