Hearing ability decreases in ageing locusts

Insects display signs of ageing, despite their short lifespan. However, the limited studies on senescence emphasize longevity or reproduction. We focused on the hearing ability of ageing adult locusts, Schistocerca gregaria. Our results indicate that the youngest adults (2 weeks post-maturity) have a greater overall neurophysiological response to sound, especially for low frequencies (<10 kHz), as well as a shorter latency to this neural response. Interestingly, when measuring displacement of the tympanal membrane that the receptor neurons directly attach to, we found movement is not directly correlated with neural response. Therefore, we suggest the enhanced response in younger animals is due to the condition of their tissues (e.g. elasticity). Secondly, we found the sexes do not have the same responses, particularly at 4 weeks post-adult moult. We propose female reproductive condition reduces their ability to receive sounds. Overall our results indicate older animals, especially females, are less sensitive to sounds

Optimization of a bio-inspired sound localization sensor for high directional sensitivity

Miniaturization of sound localization sensors arrays is heavily constrained by the limited directional cues in intensity difference and phase difference available at the microscale. Micro-Electro Mechanical System (MEMS) sound localization sensors inspired by the auditory system of Ormia ochracea offer a potential solution to this problem by the apparent amplification of the available intensity and phase difference between the measurement points. An inherent limitation of these existing systems is that significant amplification of these cues is only available at or close to one of the resonant frequencies of the device, severely limiting it application as a directional microphone. Here we present the process of optimization of a sound localization sensor for the maximum amplification of directional cues across a narrow bandwidth, increasing the signal to noise ratio and the reading accuracy for sound localization measurements

Simple ears inspire frequency agility in an engineered acoustic sensor system

Standard microphones and ultrasonic devices are generally designed with a static and flat frequency response in order to address multiple acoustic applications. However, they may not be flexible or adaptable enough to deal with some requirements. For instance, when operated in noisy environments such devices may be vulnerable to wideband background noise which will require further signal processing techniques to remove it, generally relying on digital processor units. In this work, we consider if microphones and ultrasonic devices could be designed to be sensitive only at selected frequencies of interest, whilst also providing flexibility in order to adapt to different signals of interest and to deal with environmental demands. This research exploits the concept where the “transducer becomes part of the signal processing chain” by exploring feedback processes between mechanical and electrical mechanisms that together can enhance peripheral sound processing. This capability is present within a biological acoustic system, namely in the ears of certain moths. That was used as the model of inspiration for a smart acoustic sensor system which provides dynamic adaptation of its frequency response with amplitude and time dependency according to the input signal of interest

Measured beam patterns of biomimetic receivers improve localisation performance of an ultrasonic sonar

The Beam Based Method (BBM) is a novel sonar system inspired by bat echolocation for a sonar system with one emitter and two receivers. Knowledge of the beam pattern of the receivers makes it possible to estimate the orientation of a reflecting target. In this paper, the beam pattern of four biomimetic receivers is included in the sonar system model to test which one makes the BBM localization method most accurate. Simulations are designed in MatLab and, along with the sonar system, they also model ultrasonic emission, reflection by a target and filtering through the receivers' beam pattern. All receivers are associated with similar error values in estimating target orientation. This sonar system will be built and mounted on robots for non-destructive evaluations

An analysis of end of life terminology in the carbon fiber reinforced plastic industry

While many studies and reviews into the practices conducted by industry and academia to recycle and remanufacture carbon fiber reinforced plastic (CFRP) exist, to date no investigation exists which regards the correctness of the use of terms recycling and remanufacturing. As such, this paper seeks to analyse the CFRP reuse industry’s attempt to recycle and remanufacture manufacturing waste CFRP and end of life (EOL) CFRP with an emphasis on the terminology used to describe these practices. Firstly, this paper presents a justification of the importance of using EOL terminology correctly; outlining the benefits and problems associated with using the correct and incorrect terminology. This paper finds that in the case of CFRP remanufacturing, terminology is being applied incorrectly and in the case of CFRP recycling, particular care should be taken when applying the term recycled to CFRP or stating that CFRP has been recycled. Further, this paper proposes new terminology (in keeping with EU directives) which could be adopted by industry and academia working in this area. This paper also finds that in the case of remanufacture, CFRP is incapable of being remanufactured

Hearing on the Fly: The Effects of Wing Position on Noctuid Moth Hearing

The ear of the noctuid moth has only two auditory neurons, A1 and A2, which function in detecting predatory bats. However, the noctuid\u27s ears are located on the thorax behind the wings. Therefore, as these moths need to hear during flight, it was hypothesized that wing position may affect their hearing. The wing was fixed in three different positions: up, flat and down. An additional subset of animals was measured with freely moving wings. In order to negate any possible acoustic shadowing or diffractive effects, all wings were snipped, leaving the proximal-most portion and the wing hinge intact. Results revealed that wing position plays a factor in threshold sensitivity of the less sensitive auditory neuron A2, but not in the more sensitive neuron A1. Furthermore, when the wing was set in the down position, fewer A1 action potentials were generated prior to the initiation of A2 activity. Analyzing the motion of the tympanal membrane did not reveal differences in movement due to wing position. Therefore, these neural differences arising from wing position are proposed to be due to other factors within the animal such as different muscle tensions

Multi-band asymmetric piezoelectric MEMS microphone inspired by the Ormia Ochracea

A multi-band piezoelectric directional MEMS microphone is demonstrated based on a bio-mimetic design inspired by the parasitoid fly Ormia ochracea, using the PiezoMUMPs multi-user foundry process. The device achieves a directional sound field response within four frequency bands, all lying below 15 kHz. It acts as a pressure gradient microphone with hyper-cardioid polar patterns in all frequency bands, with the measured mechanical sensitivity being in good agreement with acoustic-structural simulations conducted in COMSOL Multiphysics. The maximum experimentally measured acoustic sensitivity of the device is 19.7 mV/Pa, located at a frequency of 7972 Hz and sound incidence normal to the microphone membrane

Directional receiver for biomimetic sonar system

An ultrasonic localization method for a sonar system equipped with an emitter and two directional receivers and inspired by bat echolocation uses knowledge of the beam pattern of the receivers to estimate target orientation. Rousettus leschenaultii’s left ear constitutes the model for the design of the optimal receiver for this sonar system and 3D printing was used to fabricate receiver structures comprising of two truncated cones with an elliptical external perimeter and a parabolic flare rate in the upper part. Measurements show one receiver has a predominant lobe in the same region and with similar attenuation values as the bat ear model. The final sonar system is to be mounted on vehicular and aerial robots which require remote control for motion and sensors for estimation of each robot’s location

Radiation properties of truncated cones to enhance the beam patterns of air-coupled transducers

Radiation properties of cones are used to steer energy from the side lobes toward the center of the beam pattern of an air-coupled source. Two structures of superposed truncated cones are designed and implemented in a finite element package to modify the beam pattern of a piston model simulating an air-coupled transducer. Results show how the energy from the sides of the beam is conveyed toward the center of it thus widening the main lobe angular domain and smoothing the beam curve. This work is intended to support methods for range estimation performed with air-coupled transducers and localization strategies with broadband ultrasonic signals, as well as to investigate mathematical relationships at the base of radiation properties of conical structures

Mechanical specializations of insect ears

In this chapter some of the mechanical specializations that insects have evolved to carry out acoustic sensory tasks are reviewed. Although it is easy to perceive insect hearing organs as simplistic compared to other animals, the mechanisms involved can be complex. This chapter therefore acts as an introduction to the complexities of some insect hearing systems, as viewed from a mechanical perspective. The chapter provides some of the background knowledge readers require to investigate the subject in greater depth, while acknowledging that this subject is an active, developing, and broad area of research. Following a brief background section on the physics of sound as applied to the insect ear, the mechanical function of several insect hearing organs is discussed in relation to the different acoustic parameters that different insect species need to evaluate, such as frequency, origin, and amplitude. A further section then follows to discuss the mechanical basis of active hearing, whereby energy is added to the hearing system to condition its acoustic response, again using available examples. Finally, the chapter concludes with a discussion on the current state-of-the-art in this active research area, and makes some suggestions as to where the future may lead insect hearing mechanism researchers