Narrowband Calls Research Articles

Wing mechanics and acoustic communication of a new genus of sylvan katydid (Orthoptera: Tettigoniidae: Pseudophyllinae) from the Central Cordillera cloud forest of Colombia.

Stridulation is used by male katydids to produce sound via the rubbing together of their specialised forewings, either by sustained or interrupted sweeps of the file producing different tones and call structures. There are many species of Orthoptera that remain undescribed and their acoustic signals are unknown. This study aims to measure and quantify the mechanics of wing vibration, sound production and acoustic properties of the hearing system in a new genus of Pseudophyllinae with taxonomic descriptions of two new species. The calling behaviour and wing mechanics of males were measured using micro-scanning laser Doppler vibrometry, microscopy, and ultrasound sensitive equipment. The resonant properties of the acoustic pinnae of the ears were obtained via μ-CT scanning and 3D printed experimentation, and numerical modelling was used to validate the results. Analysis of sound recordings and wing vibrations revealed that the stridulatory areas of the right tegmen exhibit relatively narrow frequency responses and produce narrowband calls between 12 and 20 kHz. As in most Pseudophyllinae, only the right mirror is activated for sound production. The acoustic pinnae of all species were found to provide a broadband increased acoustic gain from ~40-120 kHz by up to 25 dB, peaking at almost 90 kHz which coincides with the echolocation frequency of sympatric bats. The new genus, named Satizabalus n. gen., is here derived as a new polytypic genus from the existing genus Gnathoclita, based on morphological and acoustic evidence from one described (S. sodalis n. comb.) and two new species (S. jorgevargasi n. sp. and S. hauca n. sp.). Unlike most Tettigoniidae, Satizabalus exhibits a particular form of sexual dimorphism whereby the heads and mandibles of the males are greatly enlarged compared to the females. We suggest that Satizabalus is related to the genus Trichotettix, also found in cloud forests in Colombia, and not to Gnathoclita.

The Effect of Accepted Handoff Signal Quality on the Queued Combined Guard Channel and Mobile Assisted Handoff Call Admission in 5G Networks

The effect of handoff call signal strength on the performance of the combined guard channels and mobile assisted handoff with handoff queueing is studied. If a handoff call arrives and it has an acceptable signal quality, and there are not enough channels for its service, it is queued in a finite buffer. If during its dwell time in the queue, enough channels become available, it is immediately serviced, otherwise if its dwell time is completed, and no channels are available for its service it is dropped. Two customer types, narrowband (voice calls) and wideband (data, video and media) are considered. Matrix algorithmic techniques are used to solve the balance equations to calculate the different performance measures of the system. The results indicate that when the handoff calls with good signal strength have higher probability of being accepted, the blocking probability of new calls of both types increase much more than for the handoff call dropping. Average channel utilization is also increased. Increasing the size of the queue, led to further reduction in the handoff call dropping and increase in the bandwidth utilization. When both the probability of accepting a handoff call with good quality and the queue size is increased, the blocking probability of new calls is not affected while the handoff call dropping in reduced. In all cases, it is noticed that the handoff call dropping of wideband calls is less than the handoff call dropping of narrowband calls.

Are frog calls relatively difficult to locate by mammalian predators?

Frogs call in acoustically dense choruses to attract conspecific females. Their calls can potentially reveal their location to predators, many of which are mammals. However, frogs and mammals have very different acoustic receivers and mechanisms for determining sound source direction. We argue that frog calls may have been selected so that they are harder to locate with the direction-finding mechanisms of mammals. We focus on interaural time delay (ITD) estimation using delay-line coincidence detection (place code), and a binaural excitatory/inhibitory (E/I) ITD mechanism found in mammals with small heads (population code). We identify four "strategies" which frogs may employ to exploit the weaknesses of either mechanism. The first two strategies used by the frog confound delay estimation to increase direction ambiguity using highly periodic calls or narrowband calls. The third strategy relies on using short pulses. The E/I mechanism is susceptible to noise with sounds being pulled to the medial plane when signal-to-noise ratio is low. Together, these three strategies compromise both ongoing and onset determination of location using either mechanism. Finally, frogs call in dense choruses using various means for controlling synchrony, maintaining chorus tenure, and abruptly switching off calling, all of which serve to confound location finding. Of these strategies, only chorusing adversely impacts the localization performance of frogs' acoustic receivers. We illustrate these strategies with an analysis of calls from three different frog species.

Complex wing motion during stridulation in the katydid Nastonotus foreli (Orthoptera: Tettigoniidae: Pseudophyllinae)

Male Katydids (Orthoptera: Tettigoniidae) rub together their specialised forewings to produce sound, a process known as stridulation. During wing closure, a lobe on the anal margin of the right forewing (a scraper), engages with a tooth-covered file on the left forewing. The movement of the scraper across the file produces vibrations which are amplified by a large wing cell adjacent to the scraper, the mirror. Katydids are known to stridulate with either sustained or interrupted sweeps of the file, generating resonant pure-tone (narrowband frequency) or non-resonant (broadband frequency) calls. However, some species can conserve some purity in their calls despite incorporating discrete pulses and silent intervals. This mechanism is exhibited by many Pseudophyllinae, such as Nastonotus spp., Cocconotus spp., Triencentrus spp. and Eubliastes spp. This study aims to measure and quantify the mechanics of wing stridulation in Nastonotus foreli, a Neotropical katydid that can produce, relatively narrowband calls at ≈20 kHz. It was predicted that this species will use a stridulatory mechanism involving elastic energy whereby the scraper bends and flicks along the file in periodic bursts. The calling behaviour and wing mechanics of seven males were studied using a combination of technologies (e.g. micro-scanning laser Doppler vibrometry, advanced microscopy, ultrasound-sensitive equipment and optical motion detectors) to quantify wing mechanics and structure. Analysis of recordings revealed no clear relationship between wing velocity and carrier frequency, and a pronounced distinction between wing velocity and scraper velocity during wing closure, suggesting that the scraper experiences considerable deformation. This is characteristic of the elastic scraper mechanism of stridulation. Curiously, N. foreli might have evolved to employ elastic energy to double the duration of the call, despite possessing muscles that can reach velocities high enough to produce the same frequency without the help of elastic energy.

Аналіз віртаульних схем розділення каналів в стільникових мережах зв'язку без черг і з широкосмуговими викликами даних

Two virtual schemas for partition of common pool of channels in integral cellular networks withwideband data calls are proposed. Narrowband calls are required only channel while for processingof data calls several channels are required. In one scheme two individual zones and common zone ofchannells are used by complete shared rule. In another scheme the common zone of channels are usedby handover calls only. Results of numerical experiments are given

Call admission control and resource allocation of wireless networks

In the next-generation wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) is a potential key technology. A CAC scheme is proposed for subcarrier allocation in OFDM-based wireless multi-service network. Call connection requests are divided into two classes: (i) narrowband calls and (ii) wideband calls. Traffic is characterised as batch arrival process for both classes of the calls, so that each call may request multiple subcarriers to satisfy its Quality of Service (QoS) requirement. There is a provision of buffer for narrowband calls, whereas the sub-rating scheme is used for wideband calls. The successive over-relaxation method is employed to solve the set of steady-state equations governing the traffic model. Various performance measures such as blocking probability of wide and narrowband calls, overall blocking probability of the calls and bandwidth utilisation are established. The sensitivity analysis has also been carried out to depict the effects of various system parameters on the performance measures.

Evolution of high duty cycle echolocation in bats

Duty cycle describes the relative 'on time' of a periodic signal. In bats, we argue that high duty cycle (HDC) echolocation was selected for and evolved from low duty cycle (LDC) echolocation because increasing call duty cycle enhanced the ability of echolocating bats to detect, lock onto and track fluttering insects. Most echolocators (most bats and all birds and odontocete cetaceans) use LDC echolocation, separating pulse and echo in time to avoid forward masking. They emit short duration, broadband, downward frequency modulated (FM) signals separated by relatively long periods of silence. In contrast, bats using HDC echolocation emit long duration, narrowband calls dominated by a single constant frequency (CF) separated by relatively short periods of silence. HDC bats separate pulse and echo in frequency by exploiting information contained in Doppler-shifted echoes arising from their movements relative to background objects and their prey. HDC echolocators are particularly sensitive to amplitude and frequency glints generated by the wings of fluttering insects. We hypothesize that narrowband/CF calls produced at high duty cycle, and combined with neurobiological specializations for processing Doppler-shifted echoes, were essential to the evolution of HDC echolocation because they allowed bats to detect, lock onto and track fluttering targets. This advantage was especially important in habitats with dense vegetation that produce overlapping, time-smeared echoes (i.e. background acoustic clutter). We make four specific, testable predictions arising from this hypothesis.

Dominant Glint Based Prey Localization in Horseshoe Bats: A Possible Strategy for Noise Rejection

Rhinolophidae or Horseshoe bats emit long and narrowband calls. Fluttering insect prey generates echoes in which amplitude and frequency shifts are present, i.e. glints. These glints are reliable cues about the presence of prey and also encode certain properties of the prey. In this paper, we propose that these glints, i.e. the dominant glints, are also reliable signals upon which to base prey localization. In contrast to the spectral cues used by many other bats, the localization cues in Rhinolophidae are most likely provided by self-induced amplitude modulations generated by pinnae movement. Amplitude variations in the echo not introduced by the moving pinnae can be considered as noise interfering with the localization process. The amplitude of the dominant glints is very stable. Therefore, these parts of the echoes contain very little noise. However, using only the dominant glints potentially comes at a cost. Depending on the flutter rate of the insect, a limited number of dominant glints will be present in each echo giving the bat a limited number of sample points on which to base localization. We evaluate the feasibility of a strategy under which Rhinolophidae use only dominant glints. We use a computational model of the echolocation task faced by Rhinolophidae. Our model includes the spatial filtering of the echoes by the morphology of the sonar apparatus of Rhinolophus rouxii as well as the amplitude modulations introduced by pinnae movements. Using this model, we evaluate whether the dominant glints provide Rhinolophidae with enough information to perform localization. Our simulations show that Rhinolophidae can use dominant glints in the echoes as carriers for self-induced amplitude modulations serving as localization cues. In particular, it is shown that the reduction in noise achieved by using only the dominant glints outweighs the information loss that occurs by sampling the echo.

Algorithmic approach to studying models of multirate systems with queues

Models of multirate systems that handle narrowband and broadband calls are investigated. Narrowband calls are serviced by a single channel, whereas m > 1 channels are required simultaneously for broadband calls. When the necessary number of idle channels is absent, broadband calls are queued but narrowband calls are not buffered and are accepted only if the number of idle channels is larger than a given threshold. An algorithmic approach is proposed to the calculation of service quality indices for such models, and results of numerical experiments are presented.

Quantifying bat call detection performance of humans and machines

Methods for detecting echolocation calls in field recordings of bats vary in performance and influence the effective range of a recording system. In experiments using synthetic calls from five species, human detection accuracy was 89.7+/-0.6%, compared to 76.3+/-0.8% for a model-based detector, 72.2+/-0.8% for an energy-based detector, and 98.4+/-0.2% for an optimal linear detector. The energy-based detector was 11 times faster than the model-based detector and 110 times faster than humans. Human accuracy was positively correlated with test duration (R(2)=0.43, P<0.05), meaning that higher accuracy was achieved at the expense of slower performance. Species was a significant factor determining accuracy for all detectors (P<0.001) because of call bandwidth: Narrowband calls concentrated energy in a narrower frequency band and were easier to detect. For a hypothetical recording system, range at 90% human detection accuracy varied from 10 to 35 m among species, while range dropped by approximately 20% using the automated detectors. The optimal detector outperformed humans by 5 dB and the automated methods by 9 dB. The results quantify the tradeoff between detector speed and accuracy and are useful for designing field studies of bats.

Call Admission Control Algorithms in OFDM-based Wireless Multiservice Networks

Orthogonal frequency division multiplexing (OFDM) is becoming a fundamental technology in future generation wireless communications. Call admission control is an effective mechanism to guarantee resilient, efficient, and quality-of-service (QoS) services in wireless mobile networks. In this paper, we present several call admission control algorithms for OFDM-based wireless multiservice networks. Call connection requests are differentiated into narrow-band calls and wide-band calls. For either class of calls, the traffic process is characterized as batch arrival since each call may request multiple subcarriers to satisfy its QoS requirement. The batch size is a random variable following a probability mass function (PMF) with realistically maximum value. In addition, the service times for wide-band and narrow-band calls are different. Following this, we perform a tele-traffic queueing analysis for OFDM-based wireless multiservice networks. The formulae for the significant performance metrics call blocking probability and bandwidth utilization are developed. Numerical investigations are presented to demonstrate the interaction between key parameters and performance metrics. The performance tradeoff among different call admission control algorithms is discussed. Moreover, the analytical model has been validated by simulation. The methodology as well as the result provides an efficient tool for planning next-generation OFDM-based broadband wireless access systems.

A queueing model for mixed loss-delay systems with general interarrival processes for wide-band calls

We investigate the single link mixed loss-delay FIFO system with the exponential holding time distribution, the Markovian interarrival process for the narrow-band calls, and the general independently and identically distributed interarrival process for the wide-band calls. This is achieved by combining the embedded Markov chain method and the matrix-analytic technique.

Vertical stratification in an acoustically communicating ensiferan assemblage of a tropical evergreen forest in southern India

This study provides the first quantitative description of vertical stratification in calling heights of ensiferan species constituting most of the dry-season nocturnal acoustic community of an evergreen forest in Kudremukh National Park in south-west India. Calling heights of an average of 26 individuals of each of the 20 ensiferan species were measured and subjected to an analysis of variance to test for differences in mean calling height between species and a cluster analysis to check for the presence of discontinuous calling height layers. There were significant differences in mean calling heights between species. Calling heights of different gryllid and tettigoniid species ranged from the ground to the canopy. More gryllid than tettigoniid species occupied the ground and herb layer. Our study revealed vertical stratification of calling heights, with discrete layers corresponding to the canopy, understorey and the ground layer. These clusters emerged from the raw data of calling heights of individuals without a priori distinction of layers. We found no significant correlation between the calling heights of species and call features, including mean dominant frequency of narrow band calls, mean syllable rate and mean duty cycle.

A novel admission control for fairly admitting wideband and narrowband calls

Current admission controls seeking to optimize network utilization create a bias against wideband calls. This paper proposes a BNP (buffer without preemption) model that will hold a call in a buffer rather than directly reject it when the residual bandwidth is insufficient. Such a mechanism increases the throughput since the buffer can temporarily hold a call; it also reduces the bias for wideband calls since all calls are rejected when the buffer is not empty, even when the residual bandwidth suffices for narrowband calls. The performance of the models is analyzed by solving a two-dimensional Markov chain. A modified model, BNP W, in which a waiting time threshold is added, is further offered to prevent an overlong wait for the queued call. Also, different thresholds for heterogeneous calls are set to provide equal admitting probability for them. Analytical and numerical results demonstrate that both models actually achieve fair, that is, equal or similar, admitting probability for wideband and narrowband calls.

ALTERNATION OF ECHOLOCATION CALLS IN 5 SPECIES OF AERIAL-FEEDING INSECTIVOROUS BATS FROM MALAYSIA

We describe design of echolocation signals in 5 species of aerial-hawking insectivorous bats from Malaysia. These bats forage in open spaces above the forest or in large clearings and belong to 2 families: Molossidae (Chaerephon johorensis, Mops mops, Cheiromeles torquatus) and Vespertilionidae (Hesperoptenus blanfordi, Pipistrellus stenopterus). As is typical for aerial-hawking bats, all 5 species produced narrowband calls of long duration (6‐21 ms) and low peak frequency (16‐44 kHz). However, sequences recorded from bats flying at high altitude ( .10 m) were characterized by an alternation between calls that differed in frequency of maximum energy (peak frequency), switching between high- and low-frequency calls. In some species, the types of calls also differed in duration and sound pressure level. We consider possible implications of the alternation of types of calls for the detection of prey in open spaces.

Adaptive quality of service handoff priority scheme for mobile multimedia networks

For various advantages including better utilization of radio spectrum (through frequency reuse), lower mobile transmit power requirements, and smaller and cheaper base station equipment, future wireless mobile multimedia networks are likely to adopt micro/picocellular architectures. A consequence of using small cell sizes is the increased rate of call handoffs as mobiles move between cells during the holding times of calls. In a network supporting multimedia services, the increased rate of call handoffs not only increases the signaling load on the network, but makes it very difficult for the network to guarantee the quality of service (QoS) promised to a call at setup or admission time. This paper describes an adaptive QoS handoff priority scheme which reduces the probability of call handoff failures in a mobile multimedia network with a micro/picocellular architecture. The scheme exploits the ability of most multimedia traffic types to adapt and trade off QoS with changes in the amount of bandwidth used. In this way, calls can trade QoS received for fewer handoff failures. The call level and packet level performance of the handoff scheme are studied analytically for a homogeneous network supporting a mix of wide-band and narrow-band calls. Comparisons are made to the performance of the nonpriority handoff scheme and the well-known guard-channel handoff scheme.

Call party handling using the connection view state approach: a foundation for intelligent control of multiparty calls

A number of emerging broadband services require the ability to manage multiple parties and/or media. For instance, broadband videoconferencing bridges together more than two parties. A telemedicine service could enable doctors to converse over bidirectional video and audio connections, and share X-rays and patient data over unidirectional data connections. To manage the complexity of multiple parties and media, a rigorous model of the connectivity of a call is essential. Furthermore, an application-level protocol is needed so that a broadband service may request changes to the connectivity. A promising object-oriented model and protocol is at the heart of the connection view state approach. This approach was created to enable call party handling, which may be defined as "intelligent network control of stable calls with two or more parties". The ITU-T has standardized this approach for narrowband calls. Extensions to the connection view state approach have been proposed to support broadband services.

Acoustic discrimination of passerine anti-predator signals by Australian raptors

Acoustic discrimination of anti-predator calls was examined in 11 species of Australian raptors, including 5 Falco species and 2 species of Elanus kites, by their responses to the playback of alarm and distress calls of Australian passerines. The present study investigated the ability of raptors to discriminate between alarm and distress calls that have different acoustic properties and are emitted in different behavioural contexts. The raptors were tested with broad-band calls (containing a wide range of frequencies) given as distress calls, mobbing calls and alarm calls to terrestrial predators, and with narrow-band calls (comprising a narrow range of frequencies) typically given as a response to flying predators. Raptor responses were categorised into three classes based on head orientation (or lack thereof) towards the sound source (i.e. one of 2 or 4 speakers positioned in the cage set-up); (1) ‘correct response’ – the raptor looked directly at the speaker; (2) ‘incorrect response’ – the raptor detected the sound, but oriented the head in a direction other than towards the sound source; (3) ‘no response’. All raptor species showed a higher percentage of correct responses (60–100%) for broad-frequency vocalisations and a lower percentage of correct responses (usually 0–40%) and more incorrect responses for narrow-band vocalisations. Further, all raptors showed a greater rate of overall responsiveness to broad-band alarm and distress calls than narrow-band calls, indicating a higher interest level in the former. The behavioural implications of acoustic discrimination by Australian raptors to different types of alarm call are discussed.

Echolocation call design and limits on prey size: a case study using the aerial-hawking bat Nyctalus leisleri

The echolocation calls used by Nyctalus leisleri during search phase in open air space are between 9 and 14 ms long, with the peak energy between 24 and 28 kHz. The pulses are shallowly frequency-modulated with or without an initial steep frequency-modulated component. The diet consists primarily of small flies (Diptera), including many chironomids (wingspan 9–12 mm) and yellow dung flies (Scatophaga; wingspan 24 mm), but also of some larger insects such as dung beetles (Coleoptera; Scarabaeoidea), caddis-flies (Trichoptera) and moths (Lepidoptera). The echo target strength of some prey items was measured. Contrary to models based on standard targets such as spheres or disks, the echo strength of real insects was found to be virtually independent of the emitted frequency within the 20–100 kHz frequency range. A model was used to calculate probable detection distances of the prey by the bat. Using narrow-band calls of 13.7 ± 2.7 ms duration, a bat would detect the two smallest size classes of insect at greatest range using calls of 20 kHz. The results may therefore explain why many species of large and medium sized aerial-hawking bats use low-frequency calls and still eat mostly relatively small insects. The data and model challenges the assumption that small prey are unavailable to bats using low-frequency calls.

An approximate performance model for a multislot integrated services system

An approximate model (with finite or infinite waiting room) is presented for an integrated service system with three types of traffic: a first-offered narrowband traffic, an overflow narrowband traffic, and a wideband traffic. A narrowband call requires a single server, while the number of servers required to serve a wideband call is N. The blocked narrowband calls are lost while the blocked wideband calls are delayed in a finite or infinite waiting room. Based on two assumptions with regard to the characteristics of the system, the system is resolved by decomposition. The corresponding improvements in numerical efficiency as well as in computational storage requirements are significant enough to enable use of the model within network optimization algorithms. The model provides a very good approximation for the system performance, i.e. the blocking probabilities of the two narrowband traffics, the loss probability (in the case of finite waiting room), the probability of nonwaiting, and the average waiting time of wideband traffic. >