Understanding auditory distance estimation by humpback whales: a computational approach

Ranging, the ability to judge the distance to a sound source, depends on the presence of predictable patterns of attenuation. We measured long-range sound propagation in coastal waters to assess whether humpback whales might use frequency degradation cues to range singing whales. Two types of neural networks, a multi-layer and a single-layer perceptron, were trained to classify recorded sounds by distance traveled based on their frequency content. The multi-layer network successfully classified received sounds, demonstrating that the distorting effects of underwater propagation on frequency content provide sufficient cues to estimate source distance. Normalizing received sounds with respect to ambient noise levels increased the accuracy of distance estimates by single-layer perceptrons, indicating that familiarity with background noise can potentially improve a listening whale's ability to range. To assess whether frequency patterns predictive of source distance were likely to be perceived by whales, recordings were pre-processed using a computational model of the humpback whale's peripheral auditory system. Although signals processed with this model contained less information than the original recordings, neural networks trained with these physiologically based representations estimated source distance more accurately, suggesting that listening whales should be able to range singers using distance-dependent changes in frequency content.     

On the reason for the kink in the rigidity spectra of cosmic-ray protons and helium nuclei near 230 GV

A three-component phenomenological model describing the specific features of the spectrum of cosmic-ray protons and helium nuclei in the rigidity range of 30–2×10⁵ GV is proposed. The first component corresponds to the constant background; the second, to the variable “soft” (30–500 GV) heliospheric source; and the third, to the variable “hard” (0.5–200 TV) source located inside a local bubble. The existence and variability of both sources are provided by the corresponding “surfatron accelerators,” whose operation requires the presence of an extended region with an almost uniform (in both magnitude and direction) magnetic field, orthogonally (or obliquely) to which electromagnetic waves propagate. The maximum energy to which cosmic rays can be accelerated is determined by the source size. The soft source with a size of ～100 AU is located at the periphery of the heliosphere, behind the front of the solar wind shock wave. The hard source with a size of >0.1 pc is located near the boundary of an interstellar cloud at a distance of ～0.01 pc from the Sun. The presence of a kink in the rigidity spectra of p and He near 230 GV is related to the variability of the physical conditions in the acceleration region and depends on the relation between the amplitudes and power-law exponents in the dependences of the background, soft heliospheric source, and hard near galactic source. The ultrarelativistic acceleration of p and He by an electromagnetic wave propagating in space plasma across the external magnetic field is numerically analyzed. Conditions for particle trapping by the wave and the dynamics of the particle velocity and momentum components are considered. The calculations show that, in contrast to electrons and positrons (e ⁺), the trapped protons relatively rapidly escape from the effective potential well and cease to accelerate. Due to this effect, the p and He spectra are softer than that of e ⁺. The possibility that the spectra of accelerated protons deviate from standard power-law dependences due to the surfatron mechanism is discussed.     

Distance orientation of the tick Ixodes persulcatus to the attractant factors of the prey]

The laboratory and field tests have shown that the odour is the main factor which activates ticks (Ixodes persulcatus) attraction to the host. Ticks have a sensation of a man on 15 metres distance; the number of activated ticks increases with the distance to the host and depends on the wind direction. The infrared radiation source excites only a short time activation of the ticks on 0.5-1.0 metres distance. Mechanic and sound stimulations were found to be uneffective for the ticks in the experiment.     

Avoidance Responses to Infrasound in Downstream Migrating European Silver Eels, Anguilla anguilla

In an attempt to develop an efficient acoustic fish fence, we have designed an infrasound source able to generate large nearfield particle acceleration. The source generates water movements by means of two symmetrical pistons in an air-filled cylinder with 21cm bore. The pistons are driven by eccentric coupling to an electric motor, with 5cm p.p. amplitude. The piston movements are 180° out of phase. The piston reaction forces are thus opposed, leading to vibration free operation. The submergible infrasound source is operated freely suspended in the water mass. The emitted sound frequency is 11.8Hz. The particle acceleration is about 0.01ms^–2 at a distance of 3m, corresponding to the threshold intensity for deterring effects of infrasound on Atlantic salmon smolts. The sound source was employed to test the effect of intense infrasound on migrating European silver eels. Fish confined in a tank displayed startle behaviour and prolonged stress reactions, telemetrically monitored as tachycardia, in response to intense infrasound. The field tests were carried out in the River Imsa. A trap that catches all the descending eels is installed near the river mouth. The trap was separated in four equal sections. During the periods with infrasound exposure, the proportion of silver eels entering the section closest to the sound source was reduced to 43% of the control value. In the section closest to the opposite river bank, infrasound increased the proportion of trapped eels to 144% of the control values. This shift of the migrating eels away from the infrasound source was highly significant.     

雄蝇追逐行为的分析

本文报告了在自由飞行条件下雄蝇追逐的行为实验及其分析的初步结果.其结果如下:1.追逐雄蝇水平方向偏转的角速度dF_1线性地依赖于目标蝇水平方位误差角T_1的大小.当目标在前视场中,即空间误差角|G|<π/4时,线性回归直线的斜率约为37**;而当空间误差角|G|>π/4时,线性回归直线的斜率约为6.7.2.追逐雄蝇俯仰方向偏转角速度dF_2在(-(π/2),π/2)的范围内线性依赖于俯仰误差角T_2的大小,其回归直线的斜率约为14.3.雄蝇追逐行为中,水平方位误差角频数分布的直方图呈现为峰值在零点的对称型分布;而俯仰误差角T_2频数分布的直方图是非对称型的,即仰角出现的频数大大超过俯角出现的频数.4.雄蝇主要利用了两蝇间距离变化dD的信息以及目标误差角来控制向前飞行的速度V.当误差角小时(即目标在前视场中),dD一般为负值,说明两蝇间的距离减小,而雄蝇追逐飞行的加速度A却与dD呈现正的线性关系.当误差角大时(即目标位于后视场中),dD一般为正值,说明两蝇间的距离增加.     

Hearing sensitivity in two black bass species using the auditory brainstem response approach

Recently, several bioacoustic studies have focused on the red eye bass (Micropterus coosae). One of these studies documented sound production, while the other played back sounds produced by prey items in order to determine their attractiveness to M. coosae. Surprisingly, the hearing ability of fishes in the genus Micropterus has received very little attention. The need for audiograms describing hearing in Micropterus is apparent. This study utilized the auditory brainstem response (ABR) approach to determine hearing sensitivity in terms of both sound pressure level (SPL) and particle acceleration in two black bass species, the red eye bass (M. coosae) and the Alabama bass (M. henshalli). Audiograms produced in this study expressed in both SPL and particle acceleration showed a positive relationship between hearing threshold and frequency. Micropterus coosae was most sensitive to frequencies that overlap with the peak frequencies of their vocalizations, and the vocalizations of a prey species, Cyprinella trichroistia. Bass hearing sensitivities at lower frequencies, measured in terms of particle acceleration, were similar to several sciaenid species.     

Optimization of wheat co-transformation procedure with gene cassettes resulted in an improvement in transformation frequency

Genetic manipulation using gene cassettes was applied to the elite wheat variety EM12 via particle bombardment, which allows an improvement in transformation frequency. We simultaneously transferred to wheat immature embryos with two non-linked genes, gus and bar, on either separate gene cassettes or one plasmid. The linear gene cassettes were excised and purified by restriction digestion of the plasmid, and consisted of promoters, open reading frames and terminators. No difference was observed in GUS transient expression of between gene cassettes and single whole plasmid. However, the stable transformation frequency was significantly increased to 1.1% using gene cassettes, compared with 0.4% when using single plasmid. Procedures of the efficient co-transformation with gene cassettes were developed. Factors influencing on the transformation frequency were also studied in order to optimize the procedure. These were acceleration pressure, target distance, gold particle size, the quantity ratio of gene cassettes and the age of target explants. Based on the transient and stable expression of the gus gene cassettes, optimization of transformation parameters improved the reproducibility of transformation in the elite wheat variety.     

Low frequency hearing in cephalopods

Summary Classical conditioning was employed to test the sensitivity of cephalopods to vibrations between 1 and 100 Hz generated in a standing wave acoustic tube. The animals were trained to associate sound stimuli with a weak electric shock, and the recorded conditioned responses were changes in breathing and jetting activity. Five specimens of Sepia officinalis were tested, and all responded to these low frequency sounds. The relevant stimulus parameter was particle motion rather than sound pressure. The threshold values (measured as particle acceleration) decreased towards lower frequencies in the tested range, reaching values below 4 × 10^-3 m/s². The thresholds in the most sensitive range may have been masked by the considerable background noise at the experimental site (Naples). Two individuals of Octopus vulgaris and one Loligo vulgaris were also tested, and showed a similar sensitivity to low frequency sound.     

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.     

Field hearing measurements of the Atlantic sharpnose shark Rhizoprionodon terraenovae

Field measurements of hearing thresholds were obtained from the Atlantic sharpnose shark Rhizoprionodon terraenovae using the auditory evoked potential method (AEP). The fish had most sensitive hearing at 20 Hz, the lowest frequency tested, with decreasing sensitivity at higher frequencies. Hearing thresholds were lower than AEP thresholds previously measured for the nurse shark Ginglymostoma cirratum and yellow stingray Urobatis jamaicensis at frequencies <200 Hz, and similar at 200 Hz and above. Rhizoprionodon terraenovae represents the closest comparison in terms of pelagic lifestyle to the sharks which have been observed in acoustic field attraction experiments. The sound pressure levels that would be equivalent to the particle acceleration thresholds of R. terraenovae were much higher than the sound levels which attracted closely related sharks suggesting a discrepancy between the hearing threshold experiments and the field attraction experiments.     

Hearing in the eel (Anguilla anguilla)

Summary The auditory sensitivity in the European eel (Anguilla anguilla) was measured using an acoustic tube producing sound stimuli with different ratios between sound pressure and particle motion. The upper audible frequency limit in the eel was about 300 Hz. At low frequencies the relevant stimulus parameter was particle motion, excluding involvement of the swimbladder. At the higher frequencies within the audible range the swimbladder conveyed an auditory advantage for stimuli with a high ratio between pressure and particle motion. The eel has an extremely long distance between the swimbladder and the ear. An auditory function of the swimbladder in this species therefore indicates an efficient transmission channel for the reradiated swimbladder pulsations between the bladder and the ear, although specialized anatomical adaptations for this purpose are lacking.     

3-D-orientation with the octavolateralis system.

Fish detect and localize a sound source with inner ear receptors and with the mechanosensory lateral line. The inner ear of fish is sensitive to the water displacements caused by sound waves through a direct, inertial response by hair cell epithelia of the ear. Hearing specialists, such as goldfish and herring, have accessory peripheral structures that provide additional sensitivity to the pressure component of a sound wave. While the inner ear of fish responds to the whole body motions caused by sound waves and--in case of hearing specialists--to sound pressure, the lateral line is only sensitive to water motions relative to the surface of the fish and to local pressure gradients. Using lateral line and/or acoustic input, some fish can determine the direction and the distance to a sound source. Most likely they do so by exploiting some of the mechanisms described in this paper. Piscivorous fish may use lateral line input to detect the wakes caused by swimming fish. Even in the absence of light catfish, for instance, can follow a 10 s old, three-dimensional wake left by a prey fish over distances up to 55 prey-body length.     

Prey detection in antlions: propagation of vibrational signals deep into the sand

Trap‐building antlion larvae detect their prey according to the substrate vibrations produced during movement of the prey on the sand surface. Although most studies are devoted to surface vibrational waves, in the present study, we determine the role of vibrations travelling through deeper sand layers. A behavioural experiment confirms that vibrational stimuli from prey insects on the surface of the sand stimulate the antlions buried in deeper sand layers to move towards the surface. Sand depth and particle size both have a strong effect on signal transmission. The damping coefficient (α₁₀) varies from 0.49 dB to 3.30 dB cm^?1 and depends on frequency (in the range from 100 to 300 Hz), particle size (from finest to coarse sand) and distance from the source of the vibrations. The deeper the sand, the narrower the frequency range of the signal becomes. Sand is a filter for higher frequencies. The smaller the sand particles, the more intense the filtering becomes. Fine sand with a mean sand particle size of 360 μm is a more efficient filter than coarse sand; consequently, high frequencies (> 2.5 kHz) are eliminated at a depth of 3 cm. Mean frequency depends on both depth and particle size. However, low frequency signals still propagate at a certain distance, which is biologically important in prey detection. Although the most efficient signal propagation appears to occur in coarse sand, it contains overly large particles that are inconvenient for relatively small antlion larvae. Predators seek a compromise between fine and coarse sand choosing medium sand.     

Low-Frequency Sounds Repel Male Mosquitoes <Emphasis Type="Italic">Aedes diantaeus</Emphasis> N.D.K. (Diptera,Culicidae)

We experimentally demonstrated that tonal acoustic signals with a carrier frequency of 140–200 Hz had a repellent effect on male mosquitoes (Culicidae). Swarming males of Aedes diantaeus were concentrated in a small space near the auxiliary attracting sound source which simulated the flight sound of conspecific females (carrier frequency 280–320 Hz). Then, the resulting cluster of attracted mosquitoes was stimulated with test signals of variable amplitude and carrier frequency from a second loudspeaker. The direction of mosquito flight from the source of test sounds and a decrease in their number above the attracting sound source were used as the criteria of behavioral response. Pronounced avoidance responses (negative phonotaxis) of swarming mosquitoes were observed in the range of 140–200 Hz. Most of the mosquitoes left the area above the attracting sound source within one second after the onset of the test signal. Mosquitoes mostly flew up, sideways, and backwards in relation to the test acoustic vector. We presume that mosquitoes develop defensive behavior against attacking predatory insects based on analysis of auditory information. The range of negative phonotaxis is limited at higher frequencies by the spectrum of the flight sounds of conspecific females, and in the low frequency range, by the increasing level of atmospheric noise.     

Common sole larvae survive high levels of pile-driving sound in controlled exposure experiments

In view of the rapid extension of offshore wind farms, there is an urgent need to improve our knowledge on possible adverse effects of underwater sound generated by pile-driving. Mortality and injuries have been observed in fish exposed to loud impulse sounds, but knowledge on the sound levels at which (sub-)lethal effects occur is limited for juvenile and adult fish, and virtually non-existent for fish eggs and larvae. A device was developed in which fish larvae can be exposed to underwater sound. It consists of a rigid-walled cylindrical chamber driven by an electro-dynamical sound projector. Samples of up to 100 larvae can be exposed simultaneously to a homogeneously distributed sound pressure and particle velocity field. Recorded pile-driving sounds could be reproduced accurately in the frequency range between 50 and 1000 Hz, at zero to peak pressure levels up to 210 dB re 1μPa(2) (zero to peak pressures up to 32 kPa) and single pulse sound exposure levels up to 186 dB re 1μPa(2)s. The device was used to examine lethal effects of sound exposure in common sole (Solea solea) larvae. Different developmental stages were exposed to various levels and durations of pile-driving sound. The highest cumulative sound exposure level applied was 206 dB re 1μPa(2)s, which corresponds to 100 strikes at a distance of 100 m from a typical North Sea pile-driving site. The results showed no statistically significant differences in mortality between exposure and control groups at sound exposure levels which were well above the US interim criteria for non-auditory tissue damage in fish. Although our findings cannot be extrapolated to fish larvae in general, as interspecific differences in vulnerability to sound exposure may occur, they do indicate that previous assumptions and criteria may need to be revised.     

Sound transmission and directional hearing in field crickets: neurophysiological studies outdoors

Many studies provide detailed behavioural and neurophysiological information on the ability of crickets to localize a sound source under ideal acoustic conditions, but very little is known about how they perform in real habitats. We investigated directional hearing of crickets in the field using a neurophysiological approach, by recording the activity of the two prominent, bilaterally homologous AN1 neurons simultaneously in a cricket’s habitat. The discharge and latency differences of the pair of neurons in response to conspecific chirps presented at different distances and directions were taken as a measure of directional information. The maximum hearing distance differed between individuals and weather conditions from 1 to 15 m (mean 9.2 m). Although the AN1 activity generally decreased with increasing distance, large fluctuations in the magnitude of responses occurred with distance, indicating that the intensity gradient over distance is often irregular. The directional information provided in the discharge differences of the two neurons also varied with distance. Again, there was no simple directional gradient on the transmission channel; rather, with decreasing distance to the source there were receiver locations providing suprathreshold responses, but no directional information. The consequences for the ability of field crickets to communicate acoustically close to the ground are discussed.     

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.     

An effective silencer design for artificially air conditioned environment

An effective silencer for an air conditioning duct is studied. A duct with an acoustically soft boundary is employed as an effective silencer. On the acoustically soft boundary the sound pressure is zero and it is impossible to realize such boundary in the air-borne sound field, because of the non-existence of a much lighter medium than the air. In this study, the arrangement of one-quarter wave-length acoustic tubes is employed as a soft boundary. This acoustic tube has frequency dependence, but the sound pressure becomes nearly zero at the tube mouth around the odd resonance frequency. The relation between the noise reduction efficiency and this acoustically soft boundary is examined experimentally and more than 40 dB noise reduction is obtained in a one-half octave band around the first resonance frequency. It is also made clear that more than one wave length of soft boundary is required to get enough reduction compared with the reduction obtained in the case of quite a long soft boundary.     

Bioelectrorheological model of the cell. 4. Analysis of the extensil deformation of cellular membrane in alternating electric field.

Analysis of the angular distribution of extensil mechanical stress, sigma e, generated in cytoplasmic membranes by an external oscillating electric field, is presented. Theoretical considerations show that sigma e is directly proportional to the local relative increase in membrane area and/or to the local relative decrease in its thickness. The magnitude of this stress depends on the position of the analyzed point of the membrane in relation to field direction. The maximal value, sigma eo, is reached at the cell "poles." The magnitude of sigma eo depends on electric and geometric parameters (in particular on field frequency) of the system studied. The foregoing analysis can be applied to quantitatively describe the destabilizing effects of the electric field on the cellular membrane, leading to its poration, fusion, and destruction.     

The inner ear morphology and hearing abilities of the Paddlefish (Polyodon spathula) and the Lake Sturgeon (Acipenser fulvescens)

Concern regarding the spread of silver carp (Hypopthalmichthys molitrix) and bighead carp (Aristichthysc nobilis) through the Illinois River has prompted the development of an Acoustic Fish Deterrent (AFD) system. The application of this technology has resulted in a need to understand the auditory physiology of fish other than the target species, in order to minimise the effect of the AFD barrier on the ecology of indigenous fish populations. To this end, both the structures involved in sound reception and the hearing abilities of the paddlefish (Polyodon spathula) and the lake sturgeon (Acipenser fulvescens) are studied here using a combination of morphological and physiological approaches, revealing that both fish are responsive to sounds ranging in frequency from 100 to 500 Hz. The lowest hearing thresholds from both species were acquired from frequencies in a bandwidth of between 200 and 300 Hz, with higher thresholds at 100 and 500 Hz. The rationale for studying hearing in P. spathula and A. fulvescens in particular, is the value placed on them by both the commercial caviar producing industry and by the recreational fisheries sector. The hearing abilities of twelve P. spathula and twelve A. fulvescens were tested in sound fields dominated by either sound pressure or particle motion, with the results showing that acipenseriform fish are responsive to the motion of water particles in a sound field, rather than the sound pressure component. In this study, we measure the intensity of the sound field required to evoke threshold responses using a pressure sensitive hydrophone, as pressure dominated sound fields are the most audible acoustic condition for specialists like H. molitrix and A. nobilis (the target species). The results of the auditory examination clearly show that P. spathula and A. fulvescens are not sensitive to sound pressure, and will therefore have a significantly higher deterrent threshold than H. molitrix and A. nobilis in a pressure dominated sound field.