Porpoise click classifier (PorCC): A high-accuracy classifier to study harbour porpoises (Phocoena phocoena) in the wild.

Harbour porpoises are well-suited for passive acoustic monitoring (PAM) as they produce highly stereotyped narrow-band high-frequency (NBHF) echolocation clicks. PAM systems must be coupled with a classification algorithm to identify the signals of interest. Here, the authors present a harbour porpoise click classifier (PorCC) developed in matlab, which uses the coefficients of two logistic regression models in a decision-making pathway to assign candidate signals to one of three categories: high-quality clicks (HQ), low-quality clicks (LQ), or high-frequency noise.

The anti-bat strategy of ultrasound absorption: the wings of nocturnal moths (Bombycoidea: Saturniidae) absorb more ultrasound than the wings of diurnal moths (Chalcosiinae: Zygaenoidea: Zygaenidae).

The selection pressure from echolocating bats has driven the development of a diverse range of anti-bat strategies in insects. For instance, several studies have proposed that the wings of some moths absorb a large portion of the sound energy contained in a bat's ultrasonic cry; as a result, the bat receives a dampened echo, and the moth becomes invisible to the bat. To test the hypothesis that greater exposure to bat predation drives the development of higher ultrasound absorbance, we used a small reverberation chamber to measure the ultrasound absorbance of the wings of nocturnal (Bombycoidea: Saturniidae) and diurnal moths (Chalcosiinae: Zygaenoidea: Zygaenidae).

Features in geometric receiver shapes modelling bat-like directivity patterns.

The directional properties of bat ears as receivers is a current area of interest in ultrasound research. This paper presents a new approach to analyse the relationship between morphological features and acoustical properties of the external ear of bat species. The beam pattern of Rousettus leschenaultii's right ear is measured and compared to that of receiver structures whose design is inspired by the bat ear itself and made of appropriate geometric shapes.

A beam based method for target localization: inspiration from bats' directivity and binaural reception for ultrasonic sonar.

The process of echolocation is accomplished by bats partly using the beam profiles associated with their ear shapes that allow for discrimination between different echo directions. Indeed, knowledge of the emitted signal characteristic and measurement of the echo travel time from a target make it possible to compensate for attenuation due to distance, and to focus on filtering through the receivers' beam profiles by comparing received echoes to the original signal at all frequencies in the spectrum of interest. From this basis, a beam profile method to localize a target in three-dimensional space for an ultrasonic sensor system equipped with an emitter and two receivers is presented.

An investigation of acoustic beam patterns for the sonar localization problem using a beam based method.

Target localization can be accomplished through an ultrasonic sonar system equipped with an emitter and two receivers. Time of flight of the sonar echoes allows the calculation of the distance of the target. The orientation can be estimated from knowledge of the beam pattern of the receivers and the ratio, in the frequency domain, between the emitted and the received signals after compensation for distance effects and air absorption.

Reconstruction of the signal produced by a directional sound source from remote multi-microphone recordings.

A mathematical method for reconstructing the signal produced by a directional sound source from knowledge of the same signal in the far field, i.e., microphone recordings, is developed.

A method for estimating the orientation of a directional sound source from source directivity and multi-microphone recordings: principles and application.

Taking into account directivity of real sound sources makes it possible to try solving an interesting and biologically relevant problem: estimating the orientation in three-dimensional space of a directional sound source. The source, of known directivity, produces a broadband signal (in the ultrasonic range, in this application) that is recorded by microphones whose position with respect to source is known. An analytical method to process the recorded signals and estimate source orientation is developed in this paper.