Brain-inspired sensorimotor echolocation system for confident landmark recognition.

A landmark is a familiar target in terms of the echoes that it can produce and is important for echolocation-based navigation by bats, robots, and blind humans. A brain-inspired system (BIS) achieves confident recognition, defined as classification to an arbitrarily small error probability (PE), by employing a voting process with an echo sequence. The BIS contains sensory neurons implemented with binary single-layer perceptrons trained to classify echo spectrograms with PE and generate excitatory and inhibitory votes in face neurons until a landmark-specific face neuron achieves recognition by reaching a confidence vote level (CVL).

Artificial neural network classification of foliage targets from spectrograms of sequential echoes using a biomimetic audible sonar.

Classifying foliage targets using echolocation is important for recognizing landmarks by bats using ultrasonic emissions and blind human echolocators (BEs) using palatal clicks. Previous attempts to classify foliage used ultrasonic frequencies and single sensor (monaural) detection. Motivated by the echolocation capabilities of BEs, a biomimetic sonar emitting audible clicks acquired 5600 binaural echoes from five sequential emissions that probed two foliage targets at aspect angles separated by 18°.

Artificial neural network classification of surface reflectors and volume scatterers using sequential echoes acquired with a biomimetic audible sonar.

This paper investigates classifying two target groups, surface reflectors (SR) and volume scatterers (VS), using echo envelope features. SR targets have convex surface patches that exhibit echo persistence over aspect angle, while VS targets are composed of random range-distributed and oriented reflectors producing echoes that become uncorrelated with small changes in aspect angle. The SR target group contains single-post (P1) and multiple-post (PM) types and the VS group contains Ficus benjamina (F) and Schefflera arboricola (S) foliage types with leaf areas that differ by a factor of 4.

Generating cognitive maps using echo features from a biomimetic audible sonar.

A sonar cognitive map displays target components that are specified by signal features extracted from a single binaural echo pair. A biomimetic audible sonar probes targets configured using posts connected by tangential planes. Echo envelopes are processed to extract values of eight parameters that govern the mapping process.

Forming maps of targets having multiple reflectors with a biomimetic audible sonar.

A biomimetic audible sonar mimics human echolocation by emitting clicks and sensing echoes binaurally to investigate the limitations in acoustic mapping of 2.5 dimensional targets. A monaural sonar that provides only echo time-of-flight values produces biased maps that lie outside the target surfaces.

Comparing phase-sensitive and phase-insensitive echolocation target images using a monaural audible sonar.

This paper describes phase-sensitive and phase-insensitive processing of monaural echolocation waveforms to generate target maps. Composite waveforms containing both the emission and echoes are processed to estimate the target impulse response using an audible sonar. Phase-sensitive processing yields the composite signal envelope, while phase-insensitive processing that starts with the composite waveform power spectrum yields the envelope of the autocorrelation function.

Modeling human echolocation of near-range targets with an audible sonar.

Blind humans echolocate nearby targets by emitting palatal clicks and perceiving echoes that the auditory system is not able to resolve temporally. The mechanism for perceiving near-range echoes is not known. This paper models the direct mouth-to-ear signal (MES) and the echo to show that the echo enhances the high-frequency components in the composite MES/echo signal with features that allow echolocation.

Bat wing air pressures may deflect prey structures to provide echo cues for detecting prey in clutter.

Bats have remarkable echolocation capabilities to detect prey in darkness. While it is clear how bats do this for prey that is isolated, moving, or noisy, their ability to find still and quiet prey within clutter has remained a mystery. A video published by the ChiRoPing group shows the gleaning bat Micronycteris microtis capturing a still dragonfly specimen sitting on a leaf surface.

Echolocation with bat buzz emissions: model and biomimetic sonar for elevation estimation.

Just prior to capture the Buzz II emissions of some mouth-emitting bats, such as Eptesicus fuscus, are observed to exhibit spectra having multiple peaks. This paper proposes an echolocation strategy that uses such spectra with energy concentrated in specific frequency bands for determining target elevation. A biomimetic sonar was implemented to produce a tri-modal spectrum by driving a speaker with a signal rich in harmonics.

Bat noseleaf model: echolocation function, design considerations, and experimental verification.

This paper describes a possible bat noseleaf echolocation function that improves target elevation resolution. Bats with a protruding noseleaf can rotate the lancet to act as an acoustic mirror that reflects the nostril emission, modeled as a virtual nostril that produces a delayed emission. The cancellation of the nostril and virtual nostril components at a target produces a sharp spectral notch whose frequency location relates to target elevation.

Morphology suggests noseleaf and pinnae cooperate to enhance bat echolocation.

A protruding noseleaf and concave pinna structures suggest that some bats may use these to enhance their echolocation capabilities. This paper considers two possible mechanisms that each exploit the combination of direct and delayed acoustic paths to achieve more complex emission or sensitivity echolocation patterns. The first is an emission mechanism, in which the protruding noseleaf vibrates to emit sound in both the forward and backward directions, and pinna structures reflect the backward emission to enhance the forward beam.

High-resolution adaptive spiking sonar.

A new sonar system based on the conventional 6500 ranging module is presented that generates a sequence of spikes whose temporal density is related to the strength of the received echo. This system notably improves the resolution of a previous system by shortening the discharge cycle of the integrator included in the module. The operation is controlled by a PIC18F452 device, which can adapt the duration of the discharge to changing features of the echo, providing the system with a novel adaptive behavior.

Model predicts bat pinna ridges focus high frequencies to form narrow sensitivity beams.

The pinnae of bats contain ridges whose function was previously thought to be structural. This paper suggests that ridges form a reflecting Fresnel lens that focuses high-frequency acoustic signals into the ear canal to form a narrow elevation sensitivity beam. E.

Dispersion relation for air via Kramers-Kronig analysis.

A general expression for the dispersion of acoustic waves in air is obtained by combining the attenuation coefficient given by the ISO:9613-1 standard and the twice-subtracted Kramers-Kronig relation. Good agreement is found with published data of sound velocity at different frequencies and relative humidities. The resulting expression is used to investigate changes in local dispersion with temperature and humidity.

Biosonar-inspired technology: goals, challenges and insights.

Bioinspired engineering based on biosonar systems in nature is reviewed and discussed in terms of the merits of different approaches and their results: biosonar systems are attractive technological paragons because of their capabilities, built-in task-specific knowledge, intelligent system integration and diversity. Insights from the diverse set of sensing tasks solved by bats are relevant to a wide range of application areas such as sonar, biomedical ultrasound, non-destructive testing, sensors for autonomous systems and wireless communication. Challenges in the design of bioinspired sonar systems are posed by transducer performance, actuation for sensor mobility, design, actuation and integration of beamforming baffle shapes, echo encoding for signal processing, estimation algorithms and their implementations, as well as system integration and feedback control.

Neuro-computational processing of moving sonar echoes classifies and localizes foliage.

Echoes from in situ tree trunks, similar to those observed by flying bats, are processed. A moving sonar converts echoes into spike sequences and applies neural-computational methods to classify objects and estimate passing range. Two classes of tree trunks act as retro-reflectors that generate strong echoes (SEs), identified by a locally dense spike pattern.

Binaural sonar electronic travel aid provides vibrotactile cues for landmark, reflector motion and surface texture classification.

Electronic travel aids (ETAs) for the blind commonly employ conventional time-of-flight sonars to provide range measurements, but their wide beams prevent accurate determination of object bearing. We describe a binaural sonar that detects objects over a wider bearing interval compared with a single transducer and also determines if the object lies to the left or right of the sonar axis in a robust manner. The sonar employs a pair of Polaroid 6500 ranging modules connected to Polaroid 7000 transducers operating simultaneously in a binaural array configuration.