Lower Minimum Frequencies Research Articles

Analyses of overlapping gravitational wave signals using hierarchical subtraction and joint parameter estimation

ABSTRACT In the coming years, third-generation detectors such as Einstein Telescope and Cosmic Explorer will enter the network of ground-based gravitational-wave detectors. Their current design predicts a significantly improved sensitivity band with a lower minimum frequency than existing detectors. This, combined with the increased arm length, leads to two major effects: the detection of more signals and the detection of longer signals. Both will result in a large number of overlapping signals. It has been shown that such overlapping signals can lead to biases in the recovered parameters, which would adversely affect the science extracted from the observed binary merger signals. In this work, we analyse overlapping binary black hole coalescences with two methods to analyse multisignal observations: hierarchical subtraction and joint parameter estimation. We find that these methods enable a reliable parameter extraction in most cases and that joint parameter estimation is usually more precise but comes with higher computational costs.

Terminal flourishes but not trills differ between urban and rural Chaffinch song

Animals can evade interference from anthropogenic noise using strategies such as shifting frequencies upwards or increasing the duration of their signals. In this study, we compared the time and frequency‐related characteristics of songs and rain calls of Common Chaffinches Fringilla coelebs inhabiting rural forests and an urban park in Turkey. Most of the song phrases and rain calls did not differ in any of the characteristics measured between urban and rural Chaffinches but, contrary to our predictions, terminal flourish phrases of the songs had lower minimum frequencies and broader bandwidth in urban territories. These results suggest either that noise has limited effect on the Chaffinch vocalizations or that Chaffinch vocalizations in urban habitats are less well adapted for efficient transmission.

Low-Frequency Ground Vibrations Generated by Debris Flows Detected by a Lab-Fabricated Seismometer.

A lab-fabricated ocean bottom seismometer was modified and deployed terrestrially to detect low-frequency (<10 Hz) ground vibrations produced by debris flows. A frequency−response test of the new seismometer revealed that it can detect seismic signals at frequencies of 0.3−120 Hz. Its seismic ground motion detection ability was investigated by comparing its measurements of seismic signals produced by rockfalls with those of a geophone. Two new seismometers were deployed at the Aiyuzi Stream, Nantou County, Taiwan, in September 2012. Seismic signals produced by two local earthquakes, two teleseisms, and three debris flows detected by the seismometer in 2013 and 2014 were discussed. The seismic signal frequencies of the local earthquakes and teleseisms (both approximately 1800 km apart) were 0.3−30 and <1 Hz, respectively. Moreover, seismometer measurements revealed that seismic signals generated by debris flows can have minimum frequencies as low as 2 Hz. Time-matched CCD camera images revealed that debris flow surge fronts with larger rocks have lower minimum frequencies. Finally, because the seismometer can detect low-frequency seismic waves with low spatial decay rates, it was able to detect one debris flow approximately 3 min and 40 s before it arrived.

Evolution of song and color in island birds

Island birds are often less colorful and sing different songs than their mainland counterparts. Given that trade-offs can occur in the expression of costly sexually selected traits, it is not clear whether island species with less colorful plumage than their mainland counterparts have compensated with increased complexity of song structure. To examine potential trade-offs in sexually selected traits in island birds, we examined concurrent patterns of coloration and song structure in island and mainland (sub)species across 3 widespread and speciose songbird families: Fringillidae, Meliphagidae, and Monarchidae. Phylogenetically controlled analyses revealed a shift away from white plumage and toward melanin-based plumage in island (sub)species but only in the Meliphagidae. Contrary to our predictions, we found no evidence that song structure in island birds differed from their mainland counterparts. Although a number of inverse correlations were identified between song structure and plumage coloration when all birds were considered, this pattern became weaker when only island populations were examined. Instead, we found island size affected song structure leading to a lower number of syllables and lower minimum frequency on smaller islands. Birds on smaller islands also had reduced carotenoid plumage but this pattern was only significant in the Fringillidae. These results indicate that island environments can influence the evolution of both song and color in some taxa, but that selection is tempered by island size, rather than through correlated evolution across signaling modalities.

Anthropogenic noise, song, and territorial aggression in southern house wrens

Anthropogenic noise constrains the transmission of birdsong and alters the behavior of receivers. Many birds adjust their acoustic signals to minimize the interference of anthropogenic noise on signal transmission. Birds may also change their acoustic signals to exchange information during aggressive interactions. However, it is unclear how birds deal with a potential trade‐off between adjusting their acoustic signals to better transmit in noisy environments versus mediating aggressive interactions. Additionally, we do not know how urbanization and anthropogenic noise alters the territorial behavior of receivers. We investigated the interplay among song, territorial aggression, urbanization, and anthropogenic noise, in males of the southern house wren Troglodytes aedon musculus, using recordings of spontaneous songs (non‐aggressive context) and a playback experiment simulating a male territorial intrusion (aggressive context). We found that urban wrens behaved more aggressively in response to the intruder by singing more and spent more time closer to the intruder than rural wrens regardless of noise. Males produced songs with lower minimum frequency and trills with wider frequency bandwidth and higher vocal performance under acute (playback) than relaxed (post‐playback) aggressive encounters. These results suggest that males use songs to communicate aggressive intent or fighting ability. Urban wrens produced higher‐pitched songs and trills than rural wrens irrespective of aggressive context. Urban wrens in the noisiest territories also produced the highest‐pitched trills but only in the non‐aggressive context. Rural wrens in the noisiest territories tended to produce the longest songs (non‐aggressive context) or produced the shortest songs (aggressive context). Results suggest that urbanization affects territorial and vocal behaviors in southern house wrens. Males in this species seem to primarily adjust acoustic signals in response to the territorial intruder rather than noise.

Diversification in trophic morphology and a mating signal are coupled in the early stages of sympatric divergence in crossbills

AbstractUnderstanding the mechanisms generating diversity in mating signals is critical to understanding the process of speciation. One mechanism of mating signal diversification occurs when phenotypes that experience divergent ecological selection also affect the production of mating signals, resulting in a coupling between ecological diversification and mating signal diversification. Here, we present evidence that rapid diversification in bill size has resulted in the diversification of some components of song structure in a young adaptive radiation of seed-eating finches (red crossbill, Loxia curvirostra complex). Specifically, we find that larger-billed ecotypes sing songs with lower minimum frequencies, lower syllable repetition rates and greater vocal deviation (i.e. lower performance) than smaller-billed ecotypes for pure tonal syllables. In contrast, bill size was not correlated with maximum frequency or frequency bandwidth, and we found no relationship between bill size and any song parameters in buzzy syllables. Furthermore, we found no evidence for a relationship between the degree of bill size divergence and the potential for song discrimination between sympatric ecotypes. Because bill size is correlated with some features of pure tonal syllables (which appear to be most important for courtship in crossbills) in crossbill song, our results suggest that there was an early-evolving link between ecological and mating signal diversification that may have influenced the rapid evolution of reproductive isolation between sympatric ecotypes.

Frequency and synchronisation features of a highly overlapped duet changes according to the context

ABSTRACT Territorial defence and maintaining contact are two hypotheses of duet functions. Nevertheless, the acoustic characteristics of duets in these contexts have been poorly quantified. This work aimed to compare the spectrotemporal characteristics and synchronisation in White-eared Ground-sparrow duets produced in aggressive context (i.e. territorial defence) and non-aggressive context (i.e. pair-contact). We expected to observe differences when compare duets of the same pair in each context. For this, we recorded 35 pairs in each context: territorial defence and pair-contact. We measured duration, minimum, highest, and maximum amplitude frequency. Synchronisation was measured comparing time and frequency bandwidth variation in three sections of duets produced in both contexts. In territory defence contexts, duets showed lower minimum frequencies and were produced with lower frequency synchronisation between first and middle section bandwidth; but with higher frequency synchronisation between middle and final section bandwidth. This suggests that this ground-sparrow encode context-depend information changing the frequency characteristics of duets. For example, to decrease the minimum frequency on the duets produced in territorial defence context could be understood as a most aggressive signal to the intruder, because in several species low-frequency sounds are associated with higher probability to attack the intruders or with larger and dominant individuals.

Effects of mining truck traffic on cricket calling activity.

Anthropogenic noise is a global pollutant and several studies have identified its impact on wildlife. This research shows how the noise produced by mining affects crickets' acoustic communication. Two passive acoustic monitoring devices (SMII) were installed in a forest fragment located at 500 m from the Brucutu Mine in Brazil. Another two SMII were installed distant 2500 from the mine. The equipment was configured to record from 17:00 to 05:00 h during seven days in April 2013. The authors analyzed the spectral characteristics of acoustic activity of three species of crickets (Anaxipha sp., Gryllus sp., and a Podoscirtinae species) before, during, and after the passing of mine trucks. For comparison the authors analyzed the acoustic characteristics for Anaxipha sp. and Gryllus sp. found in the distant site. Results showed a calling interruption for all the species during truck transit. Gryllus sp. emitted calls with higher maximum frequencies, average power, and larger bandwidth in the site close to the mine. Podoscirtinae species emitted calls with lower minimum frequencies, higher average power, and large bandwidth in the close site. The authors show that insect acoustic behavior varies between areas with different levels of noise. The disruption of this behavior may have negative consequences for their reproductive success.

Effect of traffic noise on Scinax nasicus advertisement call (Amphibia, Anura)

ABSTRACT Increased anthropogenic-made sounds such as traffic noises contribute to acoustic pollution, which produces deleterious effect on song-vertebrates. We compared the advertisement call of Scinax nasicus (Cope, 1862) males in natural (as a reference or control, Site A) and Sites affected by traffic noises (Site B). Call structure was recorded and it was amplified in sonograms (software Raven Pro 1.5). Seven variables were measured on its advertisement call: duration (s), number of notes, number of pulses per note, maximum and minimum frequency (kHz), dominant frequency (kHz) and amplitude (dB). In addition, at each Site the background noise (the fundamental frequency, F0 and amplitude, dB) was measured. The amplitude of background noise reached higher values (68.02 dB) in Site B, while in Site A was lower (34.81 dB). Thus, the F0 in Site A was 6.28 kHz and in Site B it was 4.15 kHz. Frog call in noisy environment (Site B) were characterized by lesser duration (s) and number of pulses per note, higher maximum and dominant frequencies (kHz), lower minimum frequencies, and amplitude (dB) when compared with control environment (Site A). Our study highlights, that S. nasicus males shift their vocal structure in traffic noisy ponds, mainly by vocal “adjust” of their frequencies and amplitude to counteract masking effect. Finally, acoustic monitoring of anurans on noise environments should be considering the spatial, temporal and spectral overlap between noise and species-specific acoustic behaviour.

The low-frequency acoustic structure of mobbing calls differs across habitat types in three passerine families

The acoustic adaptation hypothesis predicts that animals should adaptively respond to the transmission properties of the habitat in which they communicate. Although there have been many tests of the acoustic adaptation hypothesis with birdsong, there have been very few tests with different types of bird vocalizations. Here I tested the predictions of the acoustic adaptation hypothesis with avian mobbing calls produced in closed, open and urban habitats in three families of passerine birds. I also controlled for body size and phylogeny since these are known to influence acoustic characteristics of vocalizations. I found that body size was important in duration and frequency measurements of mobbing call acoustic structure. Phylogeny explained acoustic variation in only some acoustic variables measured. I also found only the two low-frequency measurements to differ across habitats. First, 5% frequency (a measurement of low-frequency energy distribution) differed between species classified as occurring in predominately open or closed habitats, with species classified as closed having lower 5% frequency than species classified as open. This finding supports the prediction that species in closed habitats will have lower low frequencies than species in open habitats. Additionally, I found that species classified as urban had a lower minimum frequency. This is in direct opposition to the prediction of the acoustic adaptation hypothesis and previous findings for birdsong, where species appear to shift lower minimum frequencies upward, likely to avoid masking by anthropogenic noise. To confirm this finding, I also measured low frequency using power spectra with an amplitude threshold (i.e. threshold method) and confirmed the same result: species classified as urban had lower minimum frequencies than species classified as open or closed.

Evaluation of patient satisfaction with different hearing aids: A study of 107 patients.

We retrospectively investigated patient satisfaction with different types of hearing aids in 107 patients-60 males and 47 females, aged 8 to 84 years (mean: 53.8)-with unilateral or bilateral hearing loss, each of whom used two different hearing devices for at least 3 years per device. The International Outcome Inventory for Hearing Aids, Turkish edition (IOI-HA-TR) was used to evaluate satisfaction levels; we also calculated our own total individual subjective satisfaction (TISS) scores. We divided 16 different hearing devices into two types: device 1 and device 2; on average, device 2 had more channels, a lower minimum frequency, and a higher maximum frequency. We found that the IOI-HA-TR scores and TISS scores were higher and usage time was greater during device 2 use, and that there was a positive correlation between IOI-HA-TR and TISS scores. A total of 69 patients (64.5%) used device 2 for more than 8 hours per day, while 38 patients (35.5%) used it for 4 to 8 hours per day during the final 2 weeks of the trial. In contrast, 40 patients (37.4%) used device 1 for more than 8 hours, 50 (46.7%) used it for 4 to 8 hours, and the remaining 17 (15.9%) used it for less than 4 hours; the difference in the duration of use of the two devices was statistically significant (p < 0.001). Younger patients and patients with more education were more satisfied with their devices than were older patients and those who were not as well educated. We conclude that devices with good technologic features such as more channels, a lower minimum frequency, and a higher maximum frequency result in better hearing. Also, based on the age difference that we observed, we recommend that psychological support be provided to older patients with aided hearing to enhance their mental health and quality of life.

The relative response of songbirds to shifts in song amplitude and song minimum frequency

Lay Summary Male birds adjust their strength of response to songs modified with increased amplitude and minimum frequency in the presence of loud human noise. In addition, territorial rival males respond more strongly to louder songs than songs with relatively lower minimum frequencies. Thus, increasing song amplitude can compensate for any loss in signal salience due to shifting songs up in minimum frequency. Increasing only song minimum frequency in the context of high noise levels could be maladaptive.

Divergence in calls but not songs in the orchard oriole complex: Icterus spurius and I. fuertesi

Birdsong has important functions in attracting and competing for mates, and song characteristics are thought to diverge rapidly during the process of speciation. In contrast, other avian vocalizations that may have non‐reproductive functions, such as calls, are thought to be more evolutionarily conserved and may diverge more slowly among taxa. This study examines differences in both male song and an acoustically simpler vocalization, the ‘jeet’ call, between two closely related taxa, Icterus spurius and I. fuertesi. A previous study comparing song syllable type sharing within and between I. spurius and I. fuertesi indicated that their songs do not differ discernibly. Here we measured 18 acoustic characteristics of their songs and found strong evidence supporting this prior finding. In contrast, we measured 17 acoustic characteristics of jeet calls and found evidence of significant divergence between the two taxa in many of these characteristics. Calls in I. fuertesi have a longer duration, a larger frequency bandwidth, a lower minimum frequency, a lower beginning frequency, and greater levels of both frequency and amplitude modulation in comparison to the calls of I. spurius. In addition, I. fuertesi calls contain two distinct parts, while the calls of I. spurius have only one part. Thus, we find evidence of divergence in the calls of the two taxa but not their songs challenging the widespread assumption that complex bird song evolves more rapidly than other types of vocalizations. Understanding divergence in multiple vocalization types as well as other behavioral, morphological, and molecular traits is important to understanding the earliest stages of speciation.

Echolocation in the bat, Rhinolophus capensis: the influence of clutter, conspecifics and prey on call design and intensity

Echolocating bats are exposed not only to the echoes of their own calls, but often the signals of conspecifics and other bats. For species emitting short, frequency modulated signals e.g. vespertilionoids, adjustments in both the frequency and time domain have been observed in such situations. However, bats using long duration, constant frequency calls may confront special challenges, since these bats should be less able to avoid temporal and frequency overlap. Here we investigated echolocation call design in the highduty cycle bat, Rhinolophus capensis, as bats flew with either a conspecific or heterospecific in a large outdoor flight-room. We compared these recordings to those made of bats flying alone in the same flight-room, and in a smaller flight room, alone, and hunting tethered moths. We found no differences in duty cycle or peak frequency of the calls of R. capensis across conditions. However, in the presence of a conspecific or the vespertilionoid, Miniopterus natalensis, R. capensis produced longer frequency-modulated downward sweeps at the terminus of their calls with lower minimum frequencies than when flying alone. In the presence of the larger high-duty cycle bat, R. clivosus, R. capensis produced shorter calls than when flying alone or with a conspecific. These changes are similar to those of vespertilionoids when flying from open to more cluttered environments. They are not similar to those differences observed in vespertilionoids when flying with other bats. Also unlike vespertilinoids, R. capensis used calls 15 dB less intense in conspecific pairs than when alone.

Is the Soft Song of the Brownish‐Flanked Bush Warbler an Aggressive Signal?

AbstractSoft songs have been detected in many songbirds, but in most species, research on soft songs has lagged behind studies of broadcast songs. In this study, we describe the acoustic features of a soft song in the brownish‐flanked bush warbler Cettia fortipes. Compared with the broadcast song, the warbler's soft song was characterized by a lower minimum frequency and longer duration, and it had a higher proportion of rapid frequency modulation notes. Using playback experiments, some in combination with mounted specimens, we found different responses to soft and broadcast songs, and we found that soft song can predict aggressive escalation (attack). We conclude that the soft song is an aggressive signal in this species.

Different vocal signals, but not prior experience, influence heterospecific from conspecific discrimination

Efficient communication between animals requires specificity to ensure that animals distinguish relevant signals from background noise. Research on discrimination between the acoustic signals of heterospecific versus conspecific animals, especially in birds, has focused on the songs produced by breeding males, in spite of the fact that animals produce other types of acoustic signals such as calls and duets. We used acoustic playback experiments to evaluate whether tropical white-eared ground-sparrows, Melozone leucotis , use calls, male solo songs and duets to discriminate conspecific from heterospecific competitors. We also evaluated whether prior experience influences competitors' discrimination by comparing responses among populations of white-eared ground-sparrows that are allopatric and sympatric with a congeneric competitor species (Prevost's ground-sparrows, Melozone biarcuatum ). White-eared ground-sparrows displayed more intense responses to conspecific vocalizations than they did to congeneric vocalizations. The duets produced in response to conspecific playback exhibited higher bandwidth and maximum frequency, lower minimum frequency and longer duration than duets produced in response to heterospecific playback. These results suggest that white-eared ground-sparrows use information encoded in vocalizations to discriminate competitors from noncompetitor species. The observed responses were not influenced by previous experience; white-eared ground-sparrows displayed similar responses whether they lived in sympatry or allopatry with the congener simulated through playback. Our results expand our understanding of how animals use different types of vocalizations to discriminate conspecific from heterospecific signals.

Which birds adjust the frequency of vocalizations in urban noise?

Urban environments present an opportunity to study the evolution of animal communication in acoustically novel habitats. Several species of birds raise the minimum frequency of vocalizations in urban noise, which is louder at lower frequencies. We recorded 12 species of birds in urban and nonurban environments, and tested whether the extent to which different species raise their minimum frequency is related to the frequency range they use. We found that raising the minimum frequency is common in urban birds and is not restricted to passerine song, but also occurs in other vocalizations of passerines and parrots. There was a strong curvilinear relation between the extent to which urban birds raise the minimum frequency and the typical minimum frequency of the species: species with intermediate minimum frequencies (around 1–1.5 kHz) raised the frequency more than species with either higher or lower minimum frequency. This suggests that high-frequency species, which are less affected by urban noise, do not need to adjust the frequency of vocalizations as much. It also suggests that for species with very low frequencies, in a frequency range where urban noise augments exponentially, increasing frequency may not overcome masking by noise efficiently, and these species may use different adaptations. This indicates that frequency differences between species influence the way in which they respond to the same communication problem (masking by low-frequency noise), and possibly also the subsequent evolution of acoustic signals.

VOCALIZATION OF TWO PALAEARCTIC SPECIES OF HAMSTER: EVERSMANN HAMSTER ALLOCRICETULUS EVERSMANNI AND GREY HAMSTER CRICETULUS MIGRATORIOS

ABSTRACT This study compared the vocalization of two sympatrically occurring species of hamster: the Eversmann hamster Allocricetulus eversmann and the Grey hamster Cricetulus migratorius. The animals were tested in conspecific pairs for 5 min. Because of the high level of aggressiveness of both species, the hamsters were separated by a mesh partition, but they had olfactory, visual and acoustic contact. Female and male Eversmann hamsters vocalized more than those of Grey hamsters. This was expressed by emission of low-frequency calls as well as by ultrasounds. The difference in vocalization between the two species was also reflected in the basic structure of ultrasonic vocalizations. Grey hamster high-frequency (ultrasonic) pulses were longer and had larger bandwidths and lower minimum frequencies than Eversmann hamster calls. Within-species comparison of vocalization indicated that males of both species emitted fewer ultrasounds than females did. These differences could have an important role in communication within and between species living in the same area and preferring the same habitats.

Temporal stability and change in a microgeographical pattern of song variation in the rufous-collared sparrow

We studied the pattern of song variation in the rufous-collared sparrow, Zonotrichia capensis, in the 1987 and 2000 breeding seasons in a 7-km 2 area covering open and closed habitats. We measured 14 quantitative song variables over a total of 390 individuals and found consistent differences between habitats in both years. In particular, songs of individuals from closed habitat sites had trills with longer trill intervals and lower frequencies than those of individuals from open habitats. This pattern of variation is interpreted as a song cline that correlates with the environmental gradient. Although this cline was stable in location and shape, it also showed several differences between years. The songs recorded during 2000 had trills with longer trill intervals and lower minimum frequencies than those recorded during 1987. Thus, this study is the first to directly document temporal changes in song variables in a Z. capensis population. This change would be expected if all the habitats studied were more closed in 2000 than in 1987, but we did not find obvious differences in habitat features between seasons. However, this modification of song structure is compatible with alternative explanations, such as subtle differences in habitat characteristics, changes in climatic variables, a delayed effect of a past modification of the environment and neutrality of the change.

Geographic Variation in the Song of the Rufous-Collared Sparrow in Eastern Argentina

Variation in trill features of Rufous-collared Sparrow (Zonotrichia capensis) song is described in three sites located on the northeast coast of Buenos Aires Province, Argentina. There is a distinctive dialect in sites supporting natural woodlands. This dialect is characterized by slower trills with lower minimum frequencies than the one present in the open grassy fields (steppe dialect). Talar dialect is absent in a site where natural woodlands have been replaced by grassy fields and open man-made parks, suggesting that the vocal tradition changed after habitat modification. Detailed analysis reveals that talar and steppe dialects intergrade in a song cline, following the vegetational ecotone. This song cline has been stable in location and features during the last decade, even though there were no geographic barriers impairing population or cultural exchange between habitats.