A moth’s ear inspires directional passive acoustic structures

Lara Díaz-García – lara.diaz-garcia@strath.ac.uk
Twitter: @laradigar23
Instagram: @laradigar

Centre for Ultrasonic Engineering, University of Strathclyde, Glasgow, Lanarkshire, G1 1RD, United Kingdom

Popular version of 2aSA1-Directional passive acoustic structures inspired by the ear of Achroia grisella, presented at the 183rd ASA Meeting.

When most people think of microphones, they think of the ones singers use or you would find in a karaoke machine, but they might not realize that much smaller microphones are all around us. Current smartphones have about three or four microphones that are small. The miniaturization of microphones is therefore a desire in technological development. These microphones are strategically placed to achieve directionality. Directionality means that the microphone’s goal is to discard undesirable noise coming from directions other than the speaker’s as well as to detect and transmit the sound signal. For hearing implant users this functionality is also desirable. Ideally, you want to be able to tell what direction a sound is coming from, as people with unimpaired hearing do.

But dealing with small size and directionality presents problems. People with unimpaired hearing can tell where sound is coming from by comparing the input received by each of our ears, conveniently sitting on opposite sides of our heads and therefore receiving sounds at slightly different times and with different intensities. The brain can do the math and compute what direction sound must be coming from. The problem is that, to use this trick, you need two microphones that are separated so the time of arrival and difference in intensity are not negligible, and that goes against microphone miniaturization. What to do if you want a small but directional microphone, then?

When looking for inspiration for novel solutions, scientists often look to nature, where energy efficiency and simple designs are prioritized in evolution. Insects are one such example that faces the challenge of directional hearing at small scales. The researchers have chosen to look at the lesser wax moth (fig 1), observed to have directional hearing in the 1980s. The males produce a mating call that the females can track even when one of their ears is pierced. This implies that, instead of using both ears as humans do, these moths’ directional hearing is achieved with just one ear.

Lesser wax moth specimen with scale bar. Image courtesy of Birgit E. Rhode (CC BY 4.0).

The working hypothesis is that directionality must be achieved by the asymmetrical shape and characteristics of the moth’s ear itself. To test this hypothesis, the researchers designed a model that resembles the moth’s ear and checked how it behaved when exposed to sound. The model consists of a thin elliptical membrane with two halves of different thicknesses. For it, they used a readily available commercial 3D printer that allows customization of the design and fabrication of samples in just a few hours. The samples were then placed on a turning surface and the behavior of the membrane in response to sound coming from different directions was investigated (fig 2). It was found that the membrane moves more when sound comes from one direction rather than all the others (fig 3), meaning the structure is therefore passively directional. This means it could inspire a single small directional microphone in the future.

Laboratory setup to turn the sample (in orange, center of the picture) and expose it to sound from the speaker (left of the picture). Researcher’s own picture.
Image adapted from Lara Díaz-García’s original paper. Sounds coming from 0º direction elicit a stronger movement in the membrane than other directions.

1pEA7 – Oscillations of drag-reducing air pocket under fast boat hull

Konstantin Matveev – matveev@wsu.edu

Washington State University
Pullman, WA 99164

Popular version of 1pEA7 – Acoustic oscillations of drag-reducing air pocket under fast boat with stepped bottom
Presented Monday afternoon, May 23, 2022
182nd ASA Meeting
Click here to read the abstract

A lot of fuel is usually consumed by a fast boat to overcome water drag. Some of this resistance is caused by water friction which scales with the hull wetted area. By injecting air under the hull bottom with a special recess and maintaining a thin but large-area air pocket, total boat drag can be decreased by up to 30%.

 

 

 

 

Boat with bottom air cavity.

However, generating and keeping the bottom air pocket in waves is rather tricky, as periodic wave pressure may excite an acoustic resonance in a compliant air cavity, resulting in large oscillations of the air cavity accompanied by significant loss of air to the surrounding water flow. The deterioration of the air pocket will drastically increase resistance of the hull, and the boat may be unable to reach sufficiently high speeds to operate in a planing regime.

Side view of air-cavity hull in waves.

 

Bottom view of air-cavity hull in waves, showing increased air leakage.

A simplified oscillator model, similar to a mass on a spring, is employed in this study to describe and simulate oscillations of the air cavity under the boat hull. The main inertia in this process is the so-called added water mass, which is a mass of an effective water volume under the air pocket, while the spring action comes from the compressibility of air inside the bottom recess.

 

 

 

Oscillator model for air cavity under hull in waves.

An air-cavity boat accelerating through waves may hit the resonance condition, when a frequency of encounter with waves coincides with the natural or preferable oscillation frequency of the air pocket under the hull. Simulations using the developed model have demonstrated that acoustic oscillations may grow in magnitude and disintegrate the air cavity. However, if the boat accelerates sufficiently fast and the time spent near the resonance state is short, then oscillations will not have enough time to amplify, and the boat can successfully reach a high speed to glide on the water surface. Alternatively, if the damping is increased, for example by baffles, morphing surfaces or even sound from underwater loudspeakers, one can suppress the oscillation growth as well. The presented model can help boat designers develop higher performance boats.

Adding Sound to Electric Vehicles Improves Pedestrian Safety

Adding Sound to Electric Vehicles Improves Pedestrian Safety

Study participants noticed cars before the minimum safe detection distance in most cases

Media Contact:
Larry Frum
AIP Media
301-209-3090
media@aip.org

SEATTLE, November 30, 2021 — While they decrease sound pollution, electric vehicles are so quiet, they can create a safety concern, particularly to the visually impaired. To address this, many governments have mandated artificial sounds be added to electric vehicles.

In the United States, regulations require vehicle sounds to be detectable at certain distances for various vehicle speeds, with faster speeds corresponding to larger detection distances. Michael Roan, from Penn State University, and Luke Neurauter, from the Virginia Tech Transportation Institute, and their team tested how well people detect electric vehicle sounds in terms of these requirements.

Roan will discuss their methods and results in the talk, “Electric Vehicle Additive Sounds: Detection results from an outdoor test for sixteen participants,” on Tuesday, Nov. 30 at 1:25 p.m. Eastern U.S. at the Hyatt Regency Seattle. The presentation is part of the 181st Meeting of the Acoustical Society of America, taking place Nov. 29-Dec. 3.

Participants in the study were seated adjacent to a lane of the Virginia Tech Transportation Institute’s Smart Road facility and pressed a button upon hearing an approaching electric vehicle. This allowed the researchers to measure the probability of detection versus distance from the vehicle, a new criterion for evaluating safety compared to the mean detection distance.

“All of the cases had mean detection ranges that exceeded the National Highway Transportation Safety Administration minimum detection distances. However, there were cases where probability of detection, even at close ranges, never reached 100%,” said Roan. “While the additive sounds greatly improve detection distances over the no sound condition, there are cases where pedestrians still missed detections.”

Even after adding sound, electric vehicles are typically quieter than standard internal combustion engine vehicles. In urban environments, they would create less sound pollution.

Roan said further studies need to be done to investigate detection when all vehicles at an intersection are electric. Additive sounds could create a complex interference pattern that may result in some loud locations and other locations with very little sound.

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3aEA7 – Interactive Systems for Immersive Spaces

Samuel Chabot – chabos2@rpi.edu Jonathan Mathews – mathej4@rpi.edu Jonas Braasch – braasj@rpi.edu
Rensselaer Polytechnic Institute
110 8th St
Troy, NY, 12180

Popular version of 3aEA7 – Multi-user interactive systems for immersive virtual environments
Presented Wednesday morning, December 01, 2021
181st ASA Meeting
Click here to read the abstract

In the past few years, immersive spaces have become increasingly popular. These spaces, most prevalently used as exhibits and galleries, incorporate large displays that completely envelop groups of people, speaker arrays, and even reactive elements that can respond to the actions of the visitors within. One of the primary challenges in creating productive applications for these environments is the integration of intuitive interaction frameworks. For users to take full advantage of these spaces, whether it be for productivity, or education, or entertainment, the interfaces used to interact with data should be both easy to understand, and provide predictable feedback. In the Collaborative Research-Augmented Immersive Virtual Environment, or CRAIVE-Lab, at Rensselaer Polytechnic Institute, we have integrated a variety of technologies to foster natural interaction with the space. First, we developed a dynamic display environment for our immersive screen, written in JavaScript, to easily create display modules for everything from images to remote desktops. Second, we have incorporated spatial information into these display objects, so that audiovisual content presented on the screen generates spatialized audio over our 128-channel speaker array at the corresponding location. Finally, we have a multi-sensor platform installed, which integrates a top-down camera array, as well as a 16-channel spherical microphone to provide continuous tracking of multiple users, voice activity detection associated with each user, and isolated audio.

By combining these technologies together, we can create a user experience within the room that encourages dynamic interaction with data. For example, delivering a presentation in this space, a process that typically consists of several file transfers and a lackluster visual experience, can now be performed with minimal setup, using the presenter’s own device, and with spatial audio when needed.

Control of lights and speakers can be done via a unified control system. Feedback from the sensor system allows display elements to be positioned relative to the user. Identified users can take ownership of specific elements on the display, and interact with the system concurrently, which makes group interactions and shared presentations far less cumbersome than with typical methods. The elements which make up the CRAIVE-Lab are not particularly novel, as far as contemporary immersive rooms are concerned. However, these elements intertwine into a network which provides functionality for the occupants that is far greater than the sum of its parts.

3pEA6 – Selective monitoring of noise emitted by vehicles involved in road traffic – Andrzej Czyżewski

Selective monitoring of noise emitted by vehicles involved in road traffic

Andrzej Czyżewski
Gdansk University of Technology
Multimedia Systems Department
80-233 Gdansk, Poland
www.multimed.org
E-mail: ac@pg.edu.pl

Tomasz Śmiałkowski
SILED Co. Ltd.
83-011 Gdańsk Poland
http://siled.pl/en/
E-mail: biuro@siled.pl

Popular version of paper 3pEA6 Selective monitoring of noise emitted by vehicles involved in road traffic
Presented Thursday afternoon, June 10, 2021
180th ASA Meeting, Acoustics in Focus

The aim of the project carried out by a Gdansk University of Technology in cooperation with an electronics company is to conduct industrial research, development, and pre-implementation works on a new product, namely an intelligent lighting platform.  This kind of street lamp system called infoLIGHT using a new generation of LEDs will become a smart city access point to various city services (Fig. 1).

Figure 1 Intelligent lighting platform – infoLIGHT project website

The research focuses on the electronics built in the street lamp using multiple sensors (Fig. 2), including an acoustic intensity probe that measures the sound intensity in three orthogonal directions, making it possible to calculate the azimuth and elevation angles, describing the sound source position.

Figure 2 – Road lamp design

The acoustic sensor is made in the form of a cube with a side of 10 mm, on the inner surfaces of which the digital MEMS microphones are mounted (Fig. 3). The acoustic probes were mounted on the lamp posts that illuminate the roadways depending on the volume of traffic.

Figure 3 Acoustical vector sensor – construction

The algorithm works in two stages. The first stage is the analysis of sound intensity signals to detect acoustic events. The second stage analyses acquired signals based on the normalized source position; its task is to determine whether the acoustic event represents what kind of a vehicle passing the sensor and detecting its movement direction. A neural network was applied for selective analysis of traffic noise (Fig. 4). The neural network depicted in Figure 4 is the so-called 1D (one-dimensional) convolution neural network. It was trained to count vehicles passing by through the analysis of noise emitted by them.

Figure 4 Neural network applied for selective analysis of traffic noise

The paper presented at the ASA Meeting explains how accurately traffic can be monitored through directional noise analysis emitted by vehicles and shows the resulting application to smart cities (see Fig. 5).

Figure 5 Comparative results of traffic analysis employing various approaches

The Polish National Centre for Research and Development (NCBR) subsidizes project No. POIR.04.01.04/2019 is entitled: infoLIGHT – “Cloud-based lighting system for smart cities” from the budget of the European Regional Development Fund.

 

 

 

 

1pEAa5 – A study on the optimal speaker position for improving sound quality of flat panel display – Sungtae Lee

Sungtae Lee, owenlee@lgdisplay.com
Kwanho Park, khpark12@lgdisplay.com
Hyungwoo Park, pphw@ssu.ac.kr
Myungjin Bae, mjbae@ssu.ac.kr
37-8, LCD-ro 8beon-gil, Wollong-myeon Paju-si, Gyeonggi-do, Korea (the Republic of)

A study on the optimal speaker position for improving sound quality of flat panel display

This “OLED Panel Speaker” was developed by attaching exciters on the back of OLED panels, which do not have backlights. Synchronizing the video and sound on screen, OLED Panel Speaker delivers clear voice and immersive sound. This technology which only can be applied to OLED, is already adopted by some TV makers and receiving great reviews and evaluations.

With the continuous development of display industry and progress of IT technology, the display is gradually becoming more advanced. Throughout the development in display technology followed by CRT to LCD and OLED, TVs have evolved to offer much better picture quality. The remarkable development of picture quality has enabled to receive positive market reactionsIn the mean time, relatively bulky speaker was hidden behind the panel to make TVs thin. TV sound could not keep up with the progress of the picture quality, until LG Display developed Flat Panel Speaker using the merit of OLED panel thickness, less than 1mm.

To realize the technology, we developed an exciter that simplifies the normal speaker structureSpecially-designed exciters are positioned at the back of the panel,
invisibly vibrate the screen to create sound.

We developed and applied an enclosure structure in order to realize “stereo sound” on one sheet of OLED panel and found positive results through vibrational mode analysis.

Depending on the shape of enclosure tape, there are Peak/Dip at a certain frequency created by standing wave. Changing the shape of peak and dip frequencies to 1/3 λ, the peak is improved by 37% from 8dB to 5 dB.

When this technology applied, the sound image moves to the center of the screen, maximizing the immersive experience and enabling the realistic sound.

Sungtae_Lee_Lay Paper