Lack of repellency of three commercial ultrasonic devices to the German cockroach （Blattodea： Blattellidae）

Three commercial ultrasonic devices （A, B, and C） were tested for their ability to repel the German cockroach, Blattella germanica （L.） （Blattodea： Blattellidae）, in Plexiglas enclosures. Device A generated peak frequencies at 26 kHz and 34 kHz, and produced a 95 ±1 dB sound pressure level （SPL） at 50 cm distance （0 dB = 20 log　10[20 μPa/ 20 μPa]）. Device B generated peak frequencies at 27 kHz and 35 kHz, and produced a 92 ± 4 dB SPL. Device C generated a wide range of frequencies between 28-42 kHz and produced an 88 ±2 dB SPL. Ultrasound from any of the three devices did not demonstrate sufficient repelling ability against the German cockroach in the tests. The result failed to provide evidence that ultrasonic technology could be used as an effective pest management tool to repel or eliminate the German cockroach.     

The acoustic behaviour of the bushcricket Tettigonia cantans II. Transmission of airborne-sound and vibration signals in the biotope

The airborne-sound and the vibratory signals produced by stridulating $\text{Tettigonia cantans}$ males, and the transmission of these signals in the natural biotope were investigated.The song of $\text{T. cantans}$ is composed of repeated uniform syllables with a rate of ca. 30/sec. Intensity approaches 100 dB SPL, 10 cm away from the animal. The spectrum shows three dominant frequency ranges around 8, 16 and 32 kHz.Airborne transmission of the song in such vegetation layers as are found in the biotopes of $\text{T. cantans}$ shows an excess attenuation which increases with frequency. The relative intensities of the frequency components of the song vary as a result of the kind of vegetation, the positions of emitter and receiver, and the separation distance. These relative differences in intensity may be useful during the phonotactic approach to conspecific partners, providing a measure of the distance from the sound source.Stridulating males also produce vibratory signals in the plants they sit on. The spectrum of these signals includes frequencies up to 8 kHz, the first dominant frequency of the song: low frequency components are induced in the plants via the legs and abdomen of the animal. The vibratory signals are transmitted mainly in the form of bending waves. Near the animal, amplitude modulation corresponds to that of the song. At greater distances, reflections and frequency-dependent propagation velocities, cause distortions of this time pattern. Transmission depends greatly on the mechanical properties of the particular plant, attenuation values of 20–50 dB/m being found. Nevertheless, in most cases, vibratory signals may be perceived up to 1.5 – 2 metres away from a stridulating male.     

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.     

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.     

Factors Affecting the Transmission of Rodent Ultrasounds in Natural Environments

Recent evidence indicates that myomorph rodent species use ultrasoniccalls as communication signals. The range over which sound communicationsignals may travel and the ease with which they may be localizeddepends on their intensity and structure and the structure ismade. It is concluded that rodent calls are mainly within therange 20–100 kHz and not longer than 300 msec, exceptfor some rat calls which last up to 3 sec. Intensities may beas high as 103 dB SPL (at 10 cm) in pups and 86 dB SPL (at 5–30cm) in adults. Bandwidths between 1–104 kHz are found.High frequency sounds are attenuated with distance more thanlower frequency sounds, mainly by atmospheric attenuation, groundattenuation and scattering. These effects are not all linearso it is difficult to predict how far rodent sounds may travelwithout making measurements under the conditions in which soundsare known to be produced by rodents in the wild. It is shownthat there is little attenuation due to scattering from vegetationin a wood inhabited by woodmice. But in grass or wheat wherefield voles may live, sounds above 20 kHz are rapidly attenuated.Attenuation may be much less in rodent runs and burrows andthis is being studied by a new spark technique.     

THE ULTRASONIC SONG OF THE MOTH AMYNA NATALIS (LEPIDOPTERA: NOCTUIDAE: ACONTIINAE)

ABSTRACT

In Malaysia, males of the noctuid moth Amyna natalis were observed producing a continuous ultrasonic song of high intensity (about 102 dB SPL measured at a distance of 10 cm). The frequency spectrum of the sound impulses had its peak between 60 and 80 kHz. During song production the animals were perching on plants and moving their wings up and down quickly. Simultaneously, by twisting the wings it seems likely that a male-specific “bubble” in the forewing functions as a tymbal, resulting in sound production.     

Sand as a medium for transmission of vibratory signals of prey in antlions Euroleon nostras (Neuroptera: Myrmeleontidae)

Abstract.  European pit-building antlions ( Euroleon nostras / Geoffroy in Fourcroy/) detect their prey by sensing the vibrations that prey generate during locomotory activity. The behavioural reactions and some of the physical properties of substrate vibrations in sand are measured to observe signal transmission through the substrate. The frequency range of the signals of four arthropod species ( Tenebrio molitor , Pyrrhocoris apterus , Formica sp. and Trachelipus rathkei ) is 0.1–4.5 kHz and acceleration values are in the range 400 μm s⁻² to 1.5 mm s⁻². Substrate particle size and the frequency of prey signals both influence the propagation properties of vibratory signals. The damping coefficient at a frequency 300 Hz varies from 0.26 to 2.61 dB cm⁻¹ and is inversely proportional to the size of the sand particle. The damping coefficient is positively correlated with the frequency of the pulses. Vibrations in finer sand are attenuated more strongly than in coarser sand and, consequently, an antlion detects its prey only at a short distance. The reaction distance is defined as the distance of the prey from the centre of the pit when the antlion begins tossing sand as a reaction to the presence of prey. The mean reaction distance is 3.3 cm in the finest sand (particle size ≤ 0.23 mm) and 12.3 cm in coarser sand (particle size 1–1.54 mm). The most convenient sands for prey detection are considered to be medium particle-sized sands.     

Call degradation in diploid and tetraploid green toads

According to the 'environmental selection' hypothesis, the physical characteristics of environments influence the evolution of long-range acoustic signals by favouring those properties that decrease sound attenuation and distortion with distance. Different environments could favour different acoustic properties and therefore contribute to the intra- and interspecific variation of calls. In the present paper, we investigate whether this hypothesis could explain the differences between the advertisement calls of three taxa of central-Asian green toads: lowland diploids, highland tetraploids and lowland tetraploids. The pattern of propagation of 12 natural calls (four for each taxon) was analysed in nine localities of Kyrgyzstan and Kazakstan. We broadcast the calls and recorded them along a trasect at distances of 2, 4, 8, 16, and 32 m from the speaker, to estimate sound attenuation and propagation. Attenuation was quantified from the oscillogram (by directly calculating the SPL of calls) and from the power spectrum (by measuring the relative amplitude of the fundamental frequency) , whereas degradation was estimated by cross-correlating spectrograms of the same call at different distances. Results show that: (1) the pattern of sound propagation significantly differs among localities in relation to the different vegetation and environmental noise; (2) in most localities, call attenuation and degradation differ significantly among the three taxa ; (3) such differences are not consistent to those expected under the hypothesis of environmental selection: independent of altitude, lowland tetraploid calls fare worse than both diploid and highland tetraploid calls, whereas diploid and highland tetraploid calls show different patterns of propagation in a few localities only.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 11–26.     

Sensory basis for sound intensity discrimination in the bushcricket Requena verticalis (Tettigoniidae, Orthoptera)

The ability of the female bushcricket, Requena verticalis, to discriminate between two conspecific sound signals that differed in sound pressure level (SPL) was tested in a two-choice paradigm. Significant discrimination was achieved with a 2-dB difference. The property of each pair of receptors to establish binaural discharge differences was investigated in electrophysiological experiments. The threshold to the conspecific signal varies for each fibre from about 40 to 90 dB SPL, allowing for a range fractionation of the hearing organ. Each pair of receptors establishes significant binaural discharge differences only within a restricted intensity range about 10 dB above threshold. Based on a model of the intensity response function of a receptor the total discharge of the 22 receptors in both ears was calculated with monaural and binaural stimulation. The profile of receptors exhibiting significant discharge differences changes with increasing SPL, from the most sensitive fibres with a characteristic frequency between 12 kHz and 35 kHz at low SPLs to the least sensitive fibres at very low and high characteristic frequencies at medium to high SPLs. The discharge difference with an intensity difference of 2 dB is rather small (4% of the total receptor activity) and limited only to a few pairs of receptors. Accepted: 8 November 1997     

Auditory response characteristics of the piebald odorous frog and their implications

The piebald odorous frog (Odorrana schmackeri), the large odorous frog (Odorrana livida) and the concave-eared torrent frog (Amolops tormotus) are sympatric species living near the same torrent streams in the vicinity of Mt. Huangshan, China. A recent study demonstrated that A. tormotus can use sound signals involving ultrasonic components for communication in a noisy environment, and another sympatric species, O. livida, can also perceive ultrasonic sound. Here we report data on the hearing range of O. schmackeri by studying auditory evoked potentials and single-unit data from the torus semicircularis. This frog exhibits its two most sensitive peaks at 2 kHz and 3.5–4.0 kHz with thresholds <42 dB SPL, with an upper frequency limit of hearing at 8.5 kHz with threshold of 87 dB SPL. The upper limit is much lower than those of O. livida and A. tormotus, at 22 and 34 kHz, respectively. It suggests that sympatric species may respond differently to similar environmental selection pressures sculpting auditory communication systems.     

Hearing Sensitivity to Shifts of Rippled-Spectrum Sound Signals in Masking Noise

The goal of the study was to enlarge knowledge of discrimination of complex sound signals by the auditory system in masking noise. For that, influence of masking noise on detection of shift of rippled spectrum was studied in normal listeners. The signal was a shift of ripple phase within a 0.5-oct wide rippled spectrum centered at 2 kHz. The ripples were frequency-proportional (throughout the band, ripple spacing was a constant proportion of the ripple center frequency). Simultaneous masker was a 0.5-oct noise below-, on-, or above the signal band. Both the low-frequency (center frequency 1 kHz) and on-frequency (the same center frequency as for the signal) maskers increased the thresholds for detecting ripple phase shift. However, the threshold dependence on the masker level was different for these two maskers. For the on-frequency masker, the masking effect primarily depended on the masker/signal ratio: the threshold steeply increased at a ratio of 5 dB, and no shift was detectable at a ratio of 10 dB. For the low-frequency masker, the masking effect primarily depended on the masker level: the threshold increased at a masker level of 80 dB SPL, and no shift was detectable at a masker level of 90 dB (for a signal level of 50 dB) or 100 dB (for a signal level of 80 dB). The high-frequency masker had little effect. The data were successfully simulated using an excitation-pattern model. In this model, the effect of the on-frequency masker appeared to be primarily due to a decrease of ripple depth. The effect of the low-frequency masker appeared due to widening of the auditory filters at high sound levels.     

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.     

Stridulation and hearing in the noctuid mothThecophora fovea (Tr.)

Summary MaleThecophora fovea (Tr.) (Noctuidae) sing continuously for several minutes by rubbing the 1. tarsal segment of the metathoracic leg against a stridulatory swelling on the hindwing. In Northern Yugoslavia (Slovenia) the males emerge in late October and start stridulating about a week later when the females emerge.The sounds are pulse trains consisting of 10–12 ms long sound pulses with main energy around 32 kHz and a PRR of 20 pulses/s. The mechanics of the sound producing apparatus was studied by activating the stridulatory swelling with short sound impulses. The impulse response of the swelling was recorded by laser vibrometry and amplitude spectra of the vibrations showed maximum velocities between 25 and 35 kHz. Hence, it seems likely that the stridulatory swelling is driven as a mechanical oscillator with a resonance frequency which determines the carrier frequency of the sounds.Audiograms of both males and females showed peak sensitivities at 25–30 kHz. The median threshold at the BF was 36 dB SPL. The peak intensity of the sound pulses was 83 dB SPL at 1 m, which should enable the moths to hear each other at distances of around 30 m. Therefore sound production inT. fovea might function in long distance calling. It is argued thatT. fovea can survive making such a noise in spite of being palatable to bats because it flies so late in the year that it is temporally isolated from bats.Abbreviations PRR pulse repetition rate - SPL sound pressure level - BF best frequency     

THE MAXIMUM RANGE OF VOCAL COMMUNICATION IN AIR BETWEEN A HARBOR SEAL (PHOCA VITULINA) PUP AND ITS MOTHER

Abstract: The transmission losses with distance of four pure tones (0.5, 1, 2, 4 kHz) were measured in the air 9 cm above the surface of the coastal waters in the Bay of Fundy. The study was conducted between May and July 1992, on warm days with low winds. The measured transmission losses were as much as 11 dB less than predicted by spherical spreading (6 dB/distance doubled), at 400 m (0.5 kHz). This enhanced sound transmission is probably due to the air temperature profile which increases with height above the water's surface. Such a profile causes sound waves to refract towards the water, thereby reducing spreading losses. High-frequency sound absorption negates enhanced transmission at 4 kHz, at distances over 500 m. On days with low winds and low ambient noise levels, a seal pup calling at 90 dB re 20, μPa at 0.5 kHz should be detectable by the mother up to 1 km away, and may be audibly recognizable up to 140 m away.     

Acoustic irradiation produced by flying moths (Lepidoptera,Noctuidae)

Characteristics of acoustic waves accompanying the flight of noctuid moths (Noctuidae) were measured. The low-frequency part of the spectrum is formed of a series of up to 17 harmonics of the wingbeat frequency (30–50 Hz) with a general tendency toward the decrease in the spectral density and the increase in the sound frequency. The root-mean-square level of the sound pressure from flapping wings was found to be 70–78 dB SPL. Besides low-frequency components, the flight of moths was accompanied by short ultrasonic pulses, which appeared with every wingbeat. Most of the spectral energy was concentrated within a range of 7–150 kHz with the main peaks at 60–110 kHz. The short-term pulses were divided into two or more subpulses with different spectra. The high-frequency pulses were produced at two phases of the wingbeat cycle: during the pronation of the wings at the highest point and at the beginning of their upward movement from the lowest point. In most of the specimens tested, the peak amplitude of sounds varied from 55 to 65 dB SPL at a distance of 6 cm from the insect body. However, in nine noctuid species, no high-frequency acoustic components were recorded. In these experiments, the acoustic flow from the flying moth within a frequency range of 2 to 20 kHz did not exceed the self-noise level of the microphone amplifier (RMS 18 dB SPL). Probable mechanisms of the high frequency acoustic emission during flight, the effect of these sounds on the auditory sensitivity of moths, and the possibility of their self-revealing to insectivorous bats are discussed. In addition, spectral characteristics of the moth echolocation clicks were more precisely determined within the higher frequency range (>100 kHz).     

Chronic exposure to low frequency noise at moderate levels causes impaired balance in mice

We are routinely exposed to low frequency noise (LFN; below 0.5 kHz) at moderate levels of 60-70 dB sound pressure level (SPL) generated from various sources in occupational and daily environments. LFN has been reported to affect balance in humans. However, there is limited information about the influence of chronic exposure to LFN at moderate levels for balance. In this study, we investigated whether chronic exposure to LFN at a moderate level of 70 dB SPL affects the vestibule, which is one of the organs responsible for balance in mice. Wild-type ICR mice were exposed for 1 month to LFN (0.1 kHz) and high frequency noise (HFN; 16 kHz) at 70 dB SPL at a distance of approximately 10-20 cm. Behavior analyses including rotarod, beam-crossing and footprint analyses showed impairments of balance in LFN-exposed mice but not in non-exposed mice or HFN-exposed mice. Immunohistochemical analysis showed a decreased number of vestibular hair cells and increased levels of oxidative stress in LFN-exposed mice compared to those in non-exposed mice. Our results suggest that chronic exposure to LFN at moderate levels causes impaired balance involving morphological impairments of the vestibule with enhanced levels of oxidative stress. Thus, the results of this study indicate the importance of considering the risk of chronic exposure to LFN at a moderate level for imbalance.     

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.     

Hearing in Cichlid Fishes under Noise Conditions

Background

Hearing thresholds of fishes are typically acquired under laboratory conditions. This does not reflect the situation in natural habitats, where ambient noise may mask their hearing sensitivities. In the current study we investigate hearing in terms of sound pressure (SPL) and particle acceleration levels (PAL) of two cichlid species within the naturally occurring range of noise levels. This enabled us to determine whether species with and without hearing specializations are differently affected by noise.

Methodology/Principal Findings

We investigated auditory sensitivities in the orange chromide Etroplus maculatus, which possesses anterior swim bladder extensions, and the slender lionhead cichlid Steatocranus tinanti, in which the swim bladder is much smaller and lacks extensions. E. maculatus was tested between 0.2 and 3kHz and S. tinanti between 0.1 and 0.5 kHz using the auditory evoked potential (AEP) recording technique. In both species, SPL and PAL audiograms were determined in the presence of quiet laboratory conditions (baseline) and continuous white noise of 110 and 130 dB RMS. Baseline thresholds showed greatest hearing sensitivity around 0.5 kHz (SPL) and 0.2 kHz (PAL) in E. maculatus and 0.2 kHz in S. tinanti. White noise of 110 dB elevated the thresholds by 0–11 dB (SPL) and 7–11 dB (PAL) in E. maculatus and by 1–2 dB (SPL) and by 1–4 dB (PAL) in S. tinanti. White noise of 130 dB elevated hearing thresholds by 13–29 dB (SPL) and 26–32 dB (PAL) in E. maculatus and 6–16 dB (SPL) and 6–19 dB (PAL) in S. tinanti.

Conclusions

Our data showed for the first time for SPL and PAL thresholds that the specialized species was masked by different noise regimes at almost all frequencies, whereas the non-specialized species was much less affected. This indicates that noise can limit sound detection and acoustic orientation differently within a single fish family.     

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.