Acoustic discrimination of passerine anti-predator signals by Australian raptors

1998 ◽  
Vol 46 (4) ◽  
pp. 369 ◽  
Author(s):  
Mark A. Jurisevic ◽  
Ken J. Sanderson
Keyword(s):  
Sound Source ◽  
Narrow Band ◽  
Broad Band ◽  
Alarm Call ◽  
Acoustic Properties ◽  
Lower Percentage ◽  
Head Orientation ◽  
Acoustic Discrimination ◽  
Wide Range ◽  
Distress Calls

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.

Perception of terrestrial and aerial alarm calls by honeyeaters and falcons

2000 ◽  
Vol 48 (2) ◽  
pp. 127 ◽  
Author(s):  
Sharon R. Wood ◽  
Ken J. Sanderson ◽  
Christopher S. Evans
Keyword(s):  
Computer System ◽  
Prey Species ◽  
Narrow Band ◽  
Broad Band ◽  
Alarm Calls ◽  
Avian Predators ◽  
Noisy Miner ◽  
Distress Calls ◽  
Manorina Melanocephala ◽  
Reduce Risk

This study tested the responses to aerial and terrestrial alarm and distress calls in an avian predator, the brown falcon, Falco berigora, and two potential avian prey species, the New Holland honeyeater, Philidonyris novaehollandiae, and noisy miner, Manorina melanocephala. Calls were delivered from a computer system at intensities 5–20 dB above background, to birds held in large cages. All birds located the broad-band alarm and distress calls easily, but they had difficulty locating the narrow-band aerial alarm calls, although they were able to detect most of these. Aerial alarm calls thus reduce risk to the caller. The performance of raptors and songbirds was similar. This result suggests that there are no reliable differences in the auditory characteristics of avian predators and prey, as have been described in species from the Northern Hemisphere.

scholarly journals Factors Affecting Acoustic Properties of Natural-Fiber-Based Materials and Composites: A Review

Textiles ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 55-85
Author(s):  
Tufail Hassan ◽  
Hafsa Jamshaid ◽  
Rajesh Mishra ◽  
Muhammad Qamar Khan ◽  
Michal Petru ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Fiber Type ◽  
Alkali Treatment ◽  
Acoustic Properties ◽  
Synthetic Fiber ◽  
Sound Insulation ◽  
Factors Affecting ◽  
Wide Range

Recently, very rapid growth has been observed in the innovations and use of natural-fiber-based materials and composites for acoustic applications due to their environmentally friendly nature, low cost, and good acoustic absorption capability. However, there are still challenges for researchers to improve the mechanical and acoustic properties of natural fiber composites. In contrast, synthetic fiber-based composites have good mechanical properties and can be used in a wide range of structural and automotive applications. This review aims to provide a short overview of the different factors that affect the acoustic properties of natural-fiber-based materials and composites. The various factors that influence acoustic performance are fiber type, fineness, length, orientation, density, volume fraction in the composite, thickness, level of compression, and design. The details of various factors affecting the acoustic behavior of the fiber-based composites are described. Natural-fiber-based composites exhibit relatively good sound absorption capability due to their porous structure. Surface modification by alkali treatment can enhance the sound absorption performance. These materials can be used in buildings and interiors for efficient sound insulation.

Synthetic individual binaural audio delivery by pinna image processing

2014 ◽  
Vol 10 (3) ◽  
pp. 239-254 ◽  
Author(s):  
Simone Spagnol ◽  
Michele Geronazzo ◽  
Davide Rocchesso ◽  
Federico Avanzini
Keyword(s):  
Sound Source ◽  
Low Complexity ◽  
Head Orientation ◽  
Sound Sources ◽  
Content Type ◽  
Localization Test ◽  
Subjective Measurements ◽  
Head Related Transfer Function ◽  
Practical Implications ◽  
Better Than

Purpose – The purpose of this paper is to present a system for customized binaural audio delivery based on the extraction of relevant features from a 2-D representation of the listener’s pinna. Design/methodology/approach – The most significant pinna contours are extracted by means of multi-flash imaging, and they provide values for the parameters of a structural head-related transfer function (HRTF) model. The HRTF model spatializes a given sound file according to the listener’s head orientation, tracked by sensor-equipped headphones, with respect to the virtual sound source. Findings – A preliminary localization test shows that the model is able to statically render the elevation of a virtual sound source better than non-individual HRTFs. Research limitations/implications – Results encourage a deeper analysis of the psychoacoustic impact that the individualized HRTF model has on perceived elevation of virtual sound sources. Practical implications – The model has low complexity and is suitable for implementation on mobile devices. The resulting hardware/software package will hopefully allow an easy and low-tech fruition of custom spatial audio to any user. Originality/value – The authors show that custom binaural audio can be successfully deployed without the need of cumbersome subjective measurements.

Calculation of Nonlinear Systems Under Narrow Band Excitation Using Equivalent Linearization and Path Continuation

2021 ◽  
Author(s):  
Alwin Förster ◽  
Lars Panning-von Scheidt
Keyword(s):  
Nonlinear Systems ◽  
Narrow Band ◽  
Gaussian White Noise ◽  
Random Excitation ◽  
Mean Value ◽  
Equivalent Linearization ◽  
Efficient Procedure ◽  
Stochastic Excitations ◽  
Wide Range ◽  
The One

Abstract Turbomachines experience a wide range of different types of excitation during operation. On the structural mechanics side, periodic or even harmonic excitations are usually assumed. For this type of excitation there are a variety of methods, both for linear and nonlinear systems. Stochastic excitation, whether in the form of Gaussian white noise or narrow band excitation, is rarely considered. As in the deterministic case, the calculations of the vibrational behavior due to stochastic excitations are even more complicated by nonlinearities, which can either be unintentionally present in the system or can be used intentionally for vibration mitigation. Regardless the origin of the nonlinearity, there are some methods in the literature, which are suitable for the calculation of the vibration response of nonlinear systems under random excitation. In this paper, the method of equivalent linearization is used to determine a linear equivalent system, whose response can be calculated instead of the one of the nonlinear system. The method is applied to different multi-degree of freedom nonlinear systems that experience narrow band random excitation, including an academic turbine blade model. In order to identify multiple and possibly ambiguous solutions, an efficient procedure is shown to integrate the mentioned method into a path continuation scheme. With this approach, it is possible to track jump phenomena or the influence of parameter variations even in case of narrow band excitation. The results of the performed calculations are the stochastic moments, i.e. mean value and variance.

Fiber Metal Acoustic Material for Gas Turbine Exhaust Environments

1989 ◽  
Vol 111 (1) ◽  
pp. 181-185
Author(s):  
M. S. Beaton
Keyword(s):  
Gas Turbine ◽  
Power Unit ◽  
Broad Band ◽  
Acoustic Energy ◽  
Acoustic Properties ◽  
Roll Forming ◽  
Sound Waves ◽  
Auxiliary Power Unit ◽  
Auxiliary Power ◽  
Fiber Metal

FELTMETAL® fiber metal acoustic materials function as broad band acoustic absorbers. Their acoustic energy absorbance occurs through viscous flow losses as sound waves pass through the tortuous pore structure of the material. A new FELTMETAL® fiber metal acoustic material has been designed for use in gas turbine auxiliary power unit exhaust environments without supplemental cooling. The physical and acoustic properties of FM 827 are discussed. Exposure tests were conducted under conditions that simulated auxiliary power unit operation. Weight gain and tensile strength data as a function of time of exposure at 650°C (1202°F) are reported. Fabrication of components with fiber metal acoustic materials is easily accomplished using standard roll forming and gas tungsten arc welding practices.

scholarly journals An Event-Based, Digital Time Difference Encoder Model Implementation for Neuromorphic Systems

2020 ◽  
Author(s):  
Daniel Gutierrez-galan ◽  
Thorben Schoepe ◽  
Juan Pedro Dominguez-Morales ◽  
Angel Jimenez-Fernandez ◽  
Elisabetta Chicca ◽  
...  
Keyword(s):  
Power Consumption ◽  
Source Localization ◽  
Sound Source ◽  
Digital Circuit ◽  
Temporal Information ◽  
Time Difference ◽  
Digital Implementation ◽  
Wide Range ◽  
Neuromorphic Systems ◽  
Event Based

Neuromorphic systems are a viable alternative to conventional systems for real-time tasks with constrained resources. Their low power consumption, compact hardware realization, and low-latency response characteristics are the key ingredients of such systems. Furthermore, the event-based signal processing approach can be exploited for reducing the computational load and avoiding data loss, thanks to its inherently sparse representation of sensed data and adaptive sampling time. In event-based systems, the information is commonly coded by the number of spikes within a specific temporal window. However, event-based signals may contain temporal information which is complex to extract when using rate coding. In this work, we present a novel digital implementation of the model, called Time Difference Encoder, for temporal encoding on event-based signals, which translates the time difference between two consecutive input events into a burst of output events. The number of output events along with the time between them encodes the temporal information. The proposed model has been implemented as a digital circuit with a configurable time constant, allowing it to be used in a wide range of sensing tasks which require the encoding of the time difference between events, such as optical flow based obstacle avoidance, sound source localization and gas source localization. This proposed bio-inspired model offers an alternative to the Jeffress model for the Interaural Time Difference estimation, validated with a sound source lateralization proof-of-concept. The model has been simulated and implemented on an FPGA, requiring 122 slice registers of hardware resources and less than 1 mW of power consumption.

scholarly journals Automated detection and association of surface waves

1994 ◽  
Vol 37 (3) ◽  
Author(s):  
R. G. North ◽  
C. R. D. Woodgold
Keyword(s):  
Surface Waves ◽  
Group Velocity ◽  
Rayleigh Waves ◽  
Arrival Time ◽  
Narrow Band ◽  
Broad Band ◽  
Detection Algorithm ◽  
Automated Detection ◽  
Short Period ◽  
Group Velocities

An algorithm for the automatic detection and association of surface waves has been developed and tested over an 18 month interval on broad band data from the Yellowknife array (YKA). The detection algorithm uses a conventional STA/LTA scheme on data that have been narrow band filtered at 20 s periods and a test is then applied to identify dispersion. An average of 9 surface waves are detected daily using this technique. Beamforming is applied to determine the arrival azimuth; at a nonarray station this could be provided by poIarization analysis. The detected surface waves are associated daily with the events located by the short period array at Yellowknife, and later with the events listed in the USGS NEIC Monthly Summaries. Association requires matching both arrival time and azimuth of the Rayleigh waves. Regional calibration of group velocity and azimuth is required. . Large variations in both group velocity and azimuth corrections were found, as an example, signals from events in Fiji Tonga arrive with apparent group velocities of 2.9 3.5 krn/s and azimuths from 5 to + 40 degrees clockwise from true (great circle) azimuth, whereas signals from Kuriles Kamchatka have velocities of 2.4 2.9 km/s and azimuths off by 35 to 0 degrees. After applying the regional corrections, surface waves are considered associated if the arrival time matches to within 0.25 km/s in apparent group velocity and the azimuth is within 30 degrees of the median expected. Over the 18 month period studied, 32% of the automatically detected surface waves were associated with events located by the Yellowknife short period array, and 34% (1591) with NEIC events; there is about 70% overlap between the two sets of events. Had the automatic detections been reported to the USGS, YKA would have ranked second (after LZH) in terms of numbers of associated surface waves for the study period of April 1991 to September 1992.

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