scholarly journals Thoracic scales of moths as a stealth coating against bat biosonar

2020 ◽  
Vol 17 (163) ◽  
pp. 20190692 ◽  
Author(s):  
Thomas R. Neil ◽  
Zhiyuan Shen ◽  
Daniel Robert ◽  
Bruce W. Drinkwater ◽  
Marc W. Holderied
Keyword(s):  
Thin Layer ◽  
Structural Parameters ◽  
Structural Similarity ◽  
Survival Advantage ◽  
Sound Insulation ◽  
Fibrous Materials ◽  
Sound Waves ◽  
Sound Energy ◽  
Sound Absorber ◽  
Ultrasonic Sound

Many moths are endowed with ultrasound-sensitive ears that serve the detection and evasion of echolocating bats. Moths lacking such ears could still gain protection from bat biosonar by using stealth acoustic camouflage, absorbing sound waves rather than reflecting them back as echoes. The thorax of a moth is bulky and hence acoustically highly reflective. This renders it an obvious target for any bat. Much of the thorax of moths is covered in hair-like scales, the layout of which is remarkably similar in structure and arrangement to natural fibrous materials commonly used in sound insulation. Despite this structural similarity, the effect of thorax scales on moth echoes has never been characterized. Here, we test whether and how moth thorax scales function as an acoustic absorber. From tomographic echo images, we find that the thin layer of thoracic scales of diurnal butterflies affects the strength of ultrasound echoes from the thorax very little, while the thorax scales of earless moths absorbs an average of 67 ± 9% of impinging ultrasonic sound energy. We show that the thorax scales of moths provide acoustic camouflage by acting as broadband (20–160 kHz) stealth coating. Modelling results suggest the scales are acting as a porous sound absorber; however, the thorax scales of moths achieve a considerably higher absorption than technical fibrous porous absorbers with the same structural parameters. Such scales, despite being thin and lightweight, constitute a broadband, multidirectional and efficient ultrasound absorber that reduces the moths' detectability to hunting bats and gives them a survival advantage.

scholarly journals Labyrinthine Structure with Subwavelength and Broadband Sound Insulation

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Heng Jiang ◽  
Yu Liu ◽  
Wenshuai Xu ◽  
Tao Yang ◽  
Dongliang Pei ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Low Frequency ◽  
Good Control ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Sound Waves ◽  
Effective Parameters ◽  
Retrieval Method ◽  
S Parameter ◽  
Broadband Sound

In this text, the combination of spiral structure and zigzag channels is introduced to design labyrinthine structures, in which sound waves can propagate alternately in the clockwise and counterclockwise directions. Finite element method and S-parameter retrieval method are used to calculate band structures, effective parameters, and transmission properties of the structures. The influences of different structural parameters on their acoustic properties are also studied. These results show labyrinthine structures have multiple bandgaps in the range of 0 Hz–1000 Hz, and the proportion of bandgaps exceeds 33%, which indicates labyrinthine structures have good broadband properties. The normalized frequency of the lowest bandgaps is far smaller than 1, which indicates the structures take good control of sound waves on subwavelength scale. Combining units with different structural parameters can achieve better sound insulation. This research provides a new kind of space-coiling structure for low-frequency and broadband sound waves control, which have excellent application prospects.

scholarly journals Non-Wovens as Sound Reducers

2018 ◽  
Vol 55 (2) ◽  
pp. 64-76
Author(s):  
D. Belakova ◽  
A. Seile ◽  
S. Kukle ◽  
T. Plamus
Keyword(s):  
Absorption Coefficient ◽  
Surface Density ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Sound Insulation ◽  
Material Structure ◽  
Sound Transmission Loss ◽  
Sound Waves ◽  
Frequency Range

Abstract Within the present study, the effect of hemp (40 wt%) and polyactide (60 wt%), non-woven surface density, thickness and number of fibre web layers on the sound absorption coefficient and the sound transmission loss in the frequency range from 50 to 5000 Hz is analysed. The sound insulation properties of the experimental samples have been determined, compared to the ones in practical use, and the possible use of material has been defined. Non-woven materials are ideally suited for use in acoustic insulation products because the arrangement of fibres produces a porous material structure, which leads to a greater interaction between sound waves and fibre structure. Of all the tested samples (A, B and D), the non-woven variant B exceeded the surface density of sample A by 1.22 times and 1.15 times that of sample D. By placing non-wovens one above the other in 2 layers, it is possible to increase the absorption coefficient of the material, which depending on the frequency corresponds to C, D, and E sound absorption classes. Sample A demonstrates the best sound absorption of all the three samples in the frequency range from 250 to 2000 Hz. In the test frequency range from 50 to 5000 Hz, the sound transmission loss varies from 0.76 (Sample D at 63 Hz) to 3.90 (Sample B at 5000 Hz).

Adjustable sound insulation frequency band through the combination of membrane-type acoustic metamaterial array

2021 ◽  
Vol 263 (1) ◽  
pp. 5869-5877
Author(s):  
Xiang Wu ◽  
TengLong Jiang ◽  
JianWang Shao ◽  
GuoMing Deng ◽  
Chang Jin
Keyword(s):  
Thin Films ◽  
Frequency Band ◽  
Transmission Loss ◽  
Structural Parameters ◽  
Sound Insulation ◽  
Acoustic Metamaterials ◽  
Additional Mass ◽  
Acoustic Metamaterial ◽  
Material Parameters ◽  
Membrane Type

Membrane-type acoustic metamaterials are thin films or plates composed of periodic units with small additional mass. A large number of studies have shown that these metamaterials exhibit tunable anti-resonance, and their transmission loss values are much higher than the corresponding quality laws. At present, most researches on membrane-type acoustic metamaterials focus on the unit cell, and the sound insulation frequency band can only be adjusted by adjusting the structural parameters and material parameters. In this paper, two kinds of acoustic metamaterials with different structures are designed, which are the center placement of the mass and the eccentric placement of the mass.The two structures have different sound insulation characteristics. By designing different array combinations of acoustic metamaterials, the sound insulation peaks of different frequency bands are obtained. This paper studies the corresponding combination law, and effectively realizes the adjustable sound insulation frequency band.

Acoustic manipulation of fractal metamaterials with negative properties and near-zero densities

2021 ◽  
Author(s):  
Guanghua Wu ◽  
Yibo Ke ◽  
Lin Zhang ◽  
Meng Tao
Keyword(s):  
High Potential ◽  
Experimental Results ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Acoustic Device

Abstract Acoustic metamaterials have high potential in diverse applications, including acoustic cloaking, sound tunneling, wavefront reshaping, and sound insulation. In the present study, new metamaterials consisting of spatial coiled units are designed and fabricated to manipulate sound waves in the range 0-1600 Hz. The effective acoustic properties and band diagrams are studied. The simulation and experimental results demonstrate that the metamaterials provide an effective and feasible approach to design acoustic device such as sound cloaking and insulators.

The Simulation of Heat and Vapour Transfer Trough Fibrous Materials

2010 ◽  
Vol 297-301 ◽  
pp. 1205-1209 ◽  
Author(s):  
Ivana Salopek Čubrić ◽  
Zenun Skenderi
Keyword(s):  
Structural Parameters ◽  
Basic Structure ◽  
Raw Material ◽  
Fibrous Materials ◽  
Vapour Permeability ◽  
Physiological Processes ◽  
Repeat Units ◽  
Materials Used

The heat and water vapour transmitting properties of fibrous materials are important factors that affect the clothing's comfort as well as the quality of special functional clothing that is worn in extreme environmental conditions. The paper introduces advanced system for the simulation of physiological processes that appear next to the human skin. Its use enables the measurement of heat and vapour transfer trough fibrous structures, as well as determination of vapour permeability and permeability index. The experiments reported here refer to the measurement of a number of fibrous materials used for the next-to-skin wear. For the measurement have been produced materials that differ either in their structure or raw material in order to observe the influences of different parameters to the transfer properties. The transfer trough fibrous materials is mainly affected by its structure that comprises of a repeat units with cellular geometry containing air pores, yarns that form basic structure and intersection points of two or more yarns. Therefore, the structure of materials is also investigated and described by means of fabric moduli. Dynamics of heat and vapour transfer is observed through the experimentally obtained data and the influence of a number of structural parameters is discussed. The statistical methods are used to qualify the effects of investigated variables on the heat and vapour resistance.

Characteristics of Range Sensor Using Spread Spectrum Ultrasonic Sound Waves

2002 ◽  
Vol 2002 (0) ◽  
pp. 54
Author(s):  
Akio Yamane ◽  
Seiichi Takenobu ◽  
Yongwoon Choi ◽  
Taketoshi Iyota ◽  
Kazuhiro Watanabe ◽  
...  
Keyword(s):  
Spread Spectrum ◽  
Sound Waves ◽  
Range Sensor ◽  
Ultrasonic Sound

scholarly journals Detecting Long Range Objects Under Radar System using Arduino

2020 ◽  
Vol 9 (4) ◽  
pp. 1504-1507
Keyword(s):  
Long Range ◽  
Radar System ◽  
Ultrasonic Sensor ◽  
Sound Waves ◽  
Servo Motor ◽  
New Approach ◽  
Ultrasonic Sound ◽  
Detection Of Objects

The increase in demand for security purpose and detection of objects using the radar system has very much popular in many occasions. A new approach of finding objects under radar using Arduino controller makes it more efficient for Detection and Ranging. The Ultrasonic sensor mounted on the servo Motor produce ultrasonic sound waves ,if an object bounce off in their path it interrupts the sound waves which produce a signal to the user by displaying on computer , laptops or on any screen . This project aims at making an efficient, cheaper and more reliable way that reflects all the possible techniques that a radar consists of

Quantitative analysis of low frequency acoustic characteristics for reverse horn by bottleneck effect analogy method

2019 ◽  
Vol 33 (16) ◽  
pp. 1950177
Author(s):  
Xiao Liang ◽  
Jiu Hui Wu ◽  
Zhuo Zhou ◽  
Zhe Chen
Keyword(s):  
Quantitative Analysis ◽  
Acoustic Waves ◽  
Low Frequency ◽  
Sound Insulation ◽  
Simple Method ◽  
Acoustic Characteristics ◽  
Bottleneck Effect ◽  
Sound Energy ◽  
Frequency Sound ◽  
Theoretical Results

Reverse horn as one of the Acoustic Black Hole (ABH) structures can be used to effectively reduce low frequency acoustic waves by focusing the sound energy. The sound waves in relatively low frequency range are focused on the tip of reverse horn, and most sound energy cannot flow out from the reverse horn’s tip. In this paper, we propose a quantitative analysis method by the bottleneck effect analogy to research the low frequency acoustic characteristics of reverse horn. Our theoretical results show that the low frequency sound wave can be focused on the tip of reverse horn, and the transmission coefficient of low frequency is proportional to the 3 power law of the reverse horn tip’s diameter. The experimental results verified our theoretical results. And the sound insulation property is studied by experiments. It is noteworthy that the insulation coefficient of two levels reverse horn whose second level tip’s diameter [Formula: see text] mm, is more than 0.92, and can increase further with the decrease of the second level horn tip’s diameter. It provides an effective and simple method for quantitatively analyzing the low frequency acoustic characteristics of the reverse horn. The proposed reverse horn has great potential applications for low frequency sound insulation control.

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