Acoustic Transformation Research Articles

Role of non-linear data processing on speech recognition task in the framework of reservoir computing

The reservoir computing neural network architecture is widely used to test hardware systems for neuromorphic computing. One of the preferred tasks for bench-marking such devices is automatic speech recognition. This task requires acoustic transformations from sound waveforms with varying amplitudes to frequency domain maps that can be seen as feature extraction techniques. Depending on the conversion method, these transformations sometimes obscure the contribution of the neuromorphic hardware to the overall speech recognition performance. Here, we quantify and separate the contributions of the acoustic transformations and the neuromorphic hardware to the speech recognition success rate. We show that the non-linearity in the acoustic transformation plays a critical role in feature extraction. We compute the gain in word success rate provided by a reservoir computing device compared to the acoustic transformation only, and show that it is an appropriate bench-mark for comparing different hardware. Finally, we experimentally and numerically quantify the impact of the different acoustic transformations for neuromorphic hardware based on magnetic nano-oscillators.

Problems and impacts associated with the acoustic environment of open-plan offices from the perspective of healthy environment

<p indent=0mm>The environmental healthfulness of office spaces can ensure the physical and mental health of office workers. The acoustic environment, in particular, influences the emotional health and work performance of them significantly. In the past decades, continuous and in-depth research conducted by the academic community has achieved abundant helpful results based on the extensive application of open-plan offices and the unique acoustic problems associated with the openness of space. This study used the Web of Science^TM core collection as the data source and employed the visual profiling tools of CiteSpace to analyse domestic and international literatures on environmental and architectural acoustics, psychoacoustics, environmental psychology, ergonomics, human factors and other related fields and then summarise research hotspots and outcomes as well as critical health-related problems and their impacts. Previous studies have reported that the influence of indoor noises is greater than that of outdoor noises. The primary source of noise in an open-plan office is “irrelevant speech”, which is a background conversation sound between other colleagues; further, “speech privacy” is the most critical problem associated with the acoustic environment of the open-plan office. The language transmission index (STI) can appropriately characterise the speech privacy of a space. Additionally, based on the research results of “Speech Prediction Method” and “STI-Ergonomic Model”, the International Organization for Standardization has formulated ISO3382-3, an acoustic environment measurement standard for open-plan offices. By utilising an appropriate translation method, China has developed and formulated the national standard GB/T36075.3. The adverse effects of the acoustic environment problems can be summarised into “psychological interference” and “cognitive interference”. The former results in “sound annoyance” and strengthens negative emotions, including fatigue, stress, and irritability, whereas the latter reduces cognitive performance and increases the cognitive load of the workers. Thus, the office workers’ acoustic environment experience and its health impact are related to the space type, work type, language type, and individual differences; however, the conclusions are insufficient. Acoustic masking is an effective methodology to improve the speech privacy in a space, but it can cause acoustic comfort problems. Exploration of the types and sound pressure levels of masking sounds, their spatial presentation, workers’ comfort experience, masking performance and efficiency, and the relationship between these factors has become a research hotspot in recent years. To ensure the healthfulness and comfort of the acoustic environment of open-plan office, further promotion at the level of theoretical research as well as technical inquiry and management should be conducted. This includes establishing an evaluation criterion that fits the characteristics of China’s office space and the Chinese language environment as soon as possible because it forms the basis for occupational health management, office building design, and acoustic environment transformation. Meanwhile, the academic investigation and application exploration of the technical methods, such as acoustic masking, is being promoted to enhance the acoustic performance of the open-plan office to obtain a technical solution that can be promoted and applied. In addition, the exploration of the sound-related environmental health issues associated with the open-plan office using advanced technologies, such as the physiological measurement technology, eye-tracking technology, and virtual reality presentations, is expected to obtain considerably significant academic benefits.

Measurement of Residual Stresses of Locomotive Wheel Treads During the Manufacturing Technological Cycle

Abstract The production of two-wheeled rolling stock represents, at first glance, a simple assembly process that significantly affects the overall functionality and safety of the vehicle. This is due to residual stresses that arise after assembly by pressing the wheel on the axle. The state of stress after assembly remains in the design has a decisive influence on the load-bearing capacity of the two-wheel drive, its lifespan but also the transfer of the pulling force in the case of locomotives. Therefore, it is very important to find suitable methods for determining residual stresses. Numerical and experimental approaches are already in place to gain information on the state of stress after compression, or during a real operation. The developed techniques and tools for estimation of residual stresses in locomotive wheel treads based on the acoustoelasticity effect using electromagnetic acoustic transformation are described in the paper. The original results of residual stress measurement in the treads during a technological cycle of locomotive wheel pair manufacturing are presented.

Comparative analysis of the shape and size of the middle ear cavity of turtles reveals no correlation with habitat ecology

The middle ear of turtles differs from other reptiles in being separated into two distinct compartments. Several ideas have been proposed as to why the middle ear is compartmentalized in turtles, most suggesting a relationship with underwater hearing. Extant turtle species span fully marine to strictly terrestrial habitats, and ecomorphological hypotheses of turtle hearing predict that this should correlate with variation in the structure of the middle ear due to differences in the fluid properties of water and air. We investigate the shape and size of the air-filled middle ear cavity of 56 extant turtles using 3D data and phylogenetic comparative analysis to test for correlations between habitat preferences and the shape and size of the middle ear cavity. Only weak correlations are found between middle ear cavity size and ecology, with aquatic taxa having proportionally smaller cavity volumes. The middle ear cavity of turtles exhibits high shape diversity among species, but we found no relationship between this shape variation and ecology. Surprisingly, the estimated acoustic transformer ratio, a key functional parameter of impedance-matching ears in vertebrates, also shows no relation to habitat preferences (aquatic/terrestrial) in turtles. We suggest that middle ear cavity shape may be controlled by factors unrelated to hearing, such as the spatial demands of surrounding cranial structures. A review of the fossil record suggests that the modern turtle ear evolved during the Early to Middle Jurassic in stem turtles broadly adapted to freshwater and terrestrial settings. This, combined with our finding that evolutionary transitions between habitats caused only weak evolutionary changes in middle ear structure, suggests that tympanic hearing in turtles evolved as a compromise between subaerial and underwater hearing.

Happy you, happy me: expressive changes on a stranger's voice recruit faster implicit processes than self-produced expressions.

In social interactions, people have to pay attention both to the ‘what’ and ‘who’. In particular, expressive changes heard on speech signals have to be integrated with speaker identity, differentiating e.g. self- and other-produced signals. While previous research has shown that self-related visual information processing is facilitated compared to non-self stimuli, evidence in the auditory modality remains mixed. Here, we compared electroencephalography (EEG) responses to expressive changes in sequence of self- or other-produced speech sounds using a mismatch negativity (MMN) passive oddball paradigm. Critically, to control for speaker differences, we used programmable acoustic transformations to create voice deviants that differed from standards in exactly the same manner, making EEG responses to such deviations comparable between sequences. Our results indicate that expressive changes on a stranger’s voice are highly prioritized in auditory processing compared to identical changes on the self-voice. Other-voice deviants generate earlier MMN onset responses and involve stronger cortical activations in a left motor and somatosensory network suggestive of an increased recruitment of resources for less internally predictable, and therefore perhaps more socially relevant, signals.

Environmental acoustic transformation and feature extraction for machine hearing

This paper explores the transformation of environmental sound waveform and feature set into a parametric type representation to be used in analysis, recognition, and identification for auditory analysis of machine hearing systems. Generally, the focus of the research and study in sound recognition is concentrated on the music and speech domains, on the other hand, there are limited in non-speech environmental recognition. We analyzed and evaluated the different current feature algorithms and methods explored for the acoustic recognition of environmental sounds, the Mel Filterbank Energies (FBEs) and Gammatone spectral coefficients (GSTC) and for classifying the sound signal the Convolutional Neural Network (CNN) was used. The result shows that GSTC performs well as a feature compared to FBEs, but FBEs tend to perform better when combined with other feature. This shows that a combination of features set is promising in obtaining a higher accuracy compared to a single feature in environmental sound classification, that is helpful in the development of the machine hearing systems.

Resonant Beam Steering and Carpet Cloaking Using an Acoustic Transformational Metascreen

The authors utilize line shaping of localized oscillations in a coupled resonant system for applications in acoustic energy transformation. Perfect control over a scattering wave front is provided by an acoustic metamaterial consisting of an array of two types of cavities. The dispersion properties of binary cells are utilized to build a flat metascreen with nearly lossless spatial-filtering characteristics. The exceptional dispersive effects are also extended to build a tunable metascreen capable of constructing virtual-scattering and carpet-cloaking objects.

Ultrasonic vibration-assisted metal forming: Constitutive modelling of acoustoplasticity and applications

This paper presents a new physics-based constitutive model to accurately describe the deformation behaviour of metals during ultrasonic vibration assisted (UVA) forming. Dislocation dynamics and acoustic energy transformation mechanisms in materials under ultrasonic vibration were considered in the modelling. A user defined subroutine was also developed for modelling the UVA forming processes using the finite element method. To assess the proposed model, upsetting forming, press forming, and incremental forming were simulated separately, and the predicted results were compared with their corresponding experiments. It was found that the application of the ultrasonic vibration can significantly decrease the material flow stress, making the material softer in forming. A large vibration amplitude results in a large reduction in flow stress. Relevant experimental measurements showed that the model has captured the material behaviour and the major mechanics in UVA forming. Different forming processes, due to their difference in tool-workpiece contact condition, would have different acoustic energy and stress transformation efficiency.

TRANSFORMATION AND SCATTERING OF SURFACE WAVES ON THE ACOUSTIC LOAD TO ULTRASONIC EVALUATION AND MEASUREMENTS. Part 2. The object to study – solid with ledge

The lack of information about the features of processes of the surface wave's transformation into volume waves and its scattering in metal objects with ledge, slots, grooves and the others is one of the obstacles to improve of the acoustical testing reliability and widening of technical application. The aim of this work was to study of mechanism of acoustical mode's transformation and determination the laws of the fields forming of scatted volume edge wave's in solids with ledge of different geometry and to suggest direction of the study application in area of acoustical testing and measurements.The features of transformation of surface waves into edge transverse and longitudinal wave modes scatted and their fields forming in the volume of the object with ledge vs. its angle of the slope front surface side (0–135°) and a dimensionless transition radius (0–10,2) varied were studied. Theoretical analysis and experimental data shown that in general case the field of the edge transverse waves in the volume of ledge can be imagined as a superposition of the field of edge waves (scatted on ledge) and accompany waves too, radiated simultaneously with the surface waves to radiate. If dimensionless size of the ledge's transition radius lesser than 1 the resulting field of the edge transverse waves is the summary field of two sources. One of them (with small aperture) is localized in the vicinity of the place of intersection of contact surface with ledge's front side surface. As it was found, the second source of the edge transverse waves – the edge head longitudinal waves to appear in the results of transformation of surface waves on the ledge′s radius transition. The structure of the edge acoustic fields including their extremes vs. ledge's angle and its radius transition, position of the surface wave's probe were experimentally studied and theoretically analyzed.Some directions of the results of researches using are the next: а) ultrasonic testing of hard-to-make technological objects in which defects have low sound reflection; b) ultrasonic structure diagnostics of solid (specimens) set far from the ultrasonic by using edge volume transverse and longitudinal modes; c) creation of new ultrasonic arrangements to sound and to receive transverse waves of different polarization.

Design of far-infrared acousto-optic tunable filter based on backward collinear interaction

The paper proposes a design of acousto-optic cell applying backward collinear interaction and acoustic mode transformation in a KRS-5 crystal. This cell may serve as an acousto-optic tunable filter for far-infrared spectral range and is able to operate both with collimated optical beams and with divergent beams forming images. The problem of acoustic mode transformation by wave reflection from the crystal facet away from symmetry planes has been solved. Polarization properties of the backward collinear interaction in optically isotropic media are discussed.

Performance Evaluation of CMUT-Based Ultrasonic Transformers for Galvanic Isolation.

This paper presents the development of a novel acoustic transformer with high galvanic isolation dedicated to power switch triggering. The transformer is based on two capacitive micromachined ultrasonic transducers layered on each side of a silicon substrate; one is the primary circuit, and the other is the secondary circuit. The thickness mode resonance of the substrate is leveraged to transmit the triggering signal. The fabrication and characterization of an initial prototype is presented in this paper. All experimental results are discussed, from the electrical impedance measurements to the power efficiency measurements, for different electrical load conditions. A comparison with a specifically developed finite-element method model is done. Simulations are finally used to identify the optimization rules of this initial prototype. It is shown that the power efficiency can be increased from 35% to 60%, and the transmitted power can be increased from 1.6 to 45 mW/Volt.

FEATURES OF ELECTROMECHANICAL ACOUSTIC ENERGY CONVERSION BY CYLINDRICAL PIEZOCERAMIC TRANSDUCERS WITH INTERNAL SCREENS IN COMPOSITION OF FLAT SYSTEMS

The problem of sound emission is considered by a system formed from cylindrical piezoceramic radiators with internal acoustically soft screens. Longitudinal axis of emitters lie in one plane. This system is characterized by the interaction of electric, mechanical and acoustic fields in the process of conversion electrical energy to acoustical energy and acoustic fields in the process of forming them in the environments. The purpose of the work is to determine the peculiarities of the electromechanical acoustic transformation of energy by cylindrical piezoceramic radiators with internal screens in the composition of flat systems, taking into account all types of interaction.The research was carried out by the method of bound fields in multiply connected domains with the use of addition theorems for the cylindrical wave functions. The physical fields arising from the emission of sound by such a system are determined by the joint solution of the system of differential equations: the wave equation; equations of motion of thin piezoceramic shells with circular polarization in displacements; the equations of forced electrostatics for piezoceramics at given boundary conditions, the conditions of conjugation of fields at the boundaries of the division of domains and electric conditions.The solution of the problem is reduced to the solution of an infinite system of linear algebraic equations with respect to unknown coefficients of field expansions.An analysis of the results of numerical calculations, performed on the basis of the obtained analytical relations, called to establish a number of features in the electromechanical acoustic transformation of energy by emitters in the composition of flat systems. They include: the role of acoustic interaction in the process of energy conversion; determination of the mechanism of quantitative assessment of the influence of interaction on these processes; the dependence of the degree of violation of the radial symmetry of the acoustic loading of the emitters on the amount of acoustic interaction; the appearance of multimodality of the mechanical field of emitters in the structure of the plane system and the dependence of the redistribution of energy between all modes on the degree of disturbance of the radial symmetry of the acoustic loading of the emitters.

Acoustic surface transformation realized by acoustic-null materials using bilayer natural materials

We propose a general method, known as acoustic surface transformation (AST), to design novel acoustic devices and study the realization of such devices by using naturally available materials in broadband acoustic frequencies. All devices designed by AST only need one anisotropic homogeneous acoustic-null material (ANM). We design the ANM by exploiting natural material-based metal-fluid structures and verify that by numerical simulation. Unlike traditional methods, no complicated mathematical calculations are needed. We only need to design the geometrical shapes of the input and output surfaces of the devices. The proposed method will pave a new road for future acoustic design.

Nonlinear response of human middle ear to high level sound

The human middle ear functions as an acoustic transformer that converts environmental sound energy into mechanical drive to stimulate the cochlea for hearing. This transformation has been demonstrated to be linear at sound levels at least as high as 125 dB. While this behavior can be expected to breakdown at some higher level, that level has not been demonstrated. In this study, we use cadaveric human ears to study middle ear nonlinear responses to high levels of sound. Tones between 200 and 10000 Hz with levels as high as 160 dB SPL are generated by a customized horn speaker and delivered to the ear canal opening. Sound pressure levels near the tympanic membrane surface are monitored by a calibrated pressure sensor. Simultaneously, Laser Doppler Vibrometry is used to record sound induced vibrations of the Umbo, in the center of the tympanic membrane, and the stapes, at the interface of the middle and inner ear. These data allow us to calculate the middle ear transfer function: the ratio of the stapes to umbo vibration. We use these measurements to investigate what is the threshold sound pressure above which the human middle ear response is no longer linear.

Structural health monitoring using torsional guided wave electromagnetic acoustic transducers

Torsional guided wave inspection is widely used for pipeline inspection. Piezoelectric and magnetostrictive transducers are most commonly used to generate torsional guided waves. These types of transducers require bonding or mechanical contact to the pipe which can result in changes over time which are undesirable for structural health monitoring. This article presents a non-contact Lorentz force–based electromagnetic acoustic transducer for torsional guided wave monitoring of pipelines. First, the excitation mechanism of the transducer is simulated by analyzing the eddy current and the static magnetic field using the finite element method. An electromagnetic acoustic transducer transformer model is presented which describes the eddy current generation transfer function and the ultrasound excitation. Independently simulated eddy current and magnetic fields are used to calculate the Lorentz force that an electromagnetic acoustic transducer array induces on the surface of a 3-in schedule 40 pipe, and an explicit finite element solver is then used to simulate the elastic wave propagation in the pipe. Then, the reception mechanism and the expected received signal levels are discussed. The construction of an experimental transducer is described, and measurement results from the transducer setup are presented. The measured and modeled performance agree well. Finally, a monitoring example is presented where an artificial defect with 3% reflection coefficient is introduced and successfully detected with the designed sensor.

Long Term Memory for Noise: Evidence of Robust Encoding of Very Short Temporal Acoustic Patterns.

Recent research has demonstrated that humans are able to implicitly encode and retain repeating patterns in meaningless auditory noise. Our study aimed at testing the robustness of long-term implicit recognition memory for these learned patterns. Participants performed a cyclic/non-cyclic discrimination task, during which they were presented with either 1-s cyclic noises (CNs) (the two halves of the noise were identical) or 1-s plain random noises (Ns). Among CNs and Ns presented once, target CNs were implicitly presented multiple times within a block, and implicit recognition of these target CNs was tested 4 weeks later using a similar cyclic/non-cyclic discrimination task. Furthermore, robustness of implicit recognition memory was tested by presenting participants with looped (shifting the origin) and scrambled (chopping sounds into 10− and 20-ms bits before shuffling) versions of the target CNs. We found that participants had robust implicit recognition memory for learned noise patterns after 4 weeks, right from the first presentation. Additionally, this memory was remarkably resistant to acoustic transformations, such as looping and scrambling of the sounds. Finally, implicit recognition of sounds was dependent on participant's discrimination performance during learning. Our findings suggest that meaningless temporal features as short as 10 ms can be implicitly stored in long-term auditory memory. Moreover, successful encoding and storage of such fine features may vary between participants, possibly depending on individual attention and auditory discrimination abilities.Significance Statement Meaningless auditory patterns could be implicitly encoded and stored in long-term memory.Acoustic transformations of learned meaningless patterns could be implicitly recognized after 4 weeks.Implicit long-term memories can be formed for meaningless auditory features as short as 10 ms.Successful encoding and long-term implicit recognition of meaningless patterns may strongly depend on individual attention and auditory discrimination abilities.

Determining the effect of the duration of alternating acoustic excitation on electromagnetic response parameters of the composite

The paper presents the results of the experimental investigation dealing with the effect of the alternating excitation acoustic pulse duration on the parameters of the electromagnetic emission caused by interaction of acoustic vibrations with inhomogeneities in the sample structure, piezoelectric inclusions and media interfaces of different dielectric properties. The model sample was epoxy resin with quartz sand as filler. The electrical component of the response was recorded with a capacitive transducer. The acoustic pulse was generated by piezoelectric transducer at frequencies of 57 kHz, 65 kHz, 74 kHz, 87.5 kHz and 94.5 kHz with the pulse duration varying from 10 gs to 100 gs. It is shown that the reduced duration of the acoustic action leads to dominance of the intrinsic frequency in the spectrum. A contribution of tensile pulses to acoustic electromagnetic transformation response generation is revealed.

An acoustic space-time and the Lorentz transformation in aeroacoustics

In this paper we introduce concepts from relativity and geometric algebra to aeroacoustics. We do this using an acoustic space-time transformation within the framework of sound propagation in uniform flows. By using Geometric Algebra we are able to provide a simple geometric interpretation to the space-time transformation, and are able to give neat and lucid derivations of the free-field Green's function for the convected wave equation and the Doppler shift for a stationary observer and a source in uniform rectilinear motion in a uniform flow.

An Acoustic Space-Time and the Lorentz Transformation in Aeroacoustics

In this paper we introduce concepts from relativity and geometric algebra to aeroacoustics. We do this using an acoustic space-time transformation within the framework of sound propagation in uniform flows. By using Geometric Algebra we are able to provide a simple geometric interpretation of the space-time transformation, and are able to give neat and lucid derivations of the free-field Green's function for the convected wave equation and the Doppler shift for a stationary observer and a source in uniform rectilinear motion in a uniform flow.

Emergence of invariant representation of vocalizations in the auditory cortex.

An essential task of the auditory system is to discriminate between different communication signals, such as vocalizations. In everyday acoustic environments, the auditory system needs to be capable of performing the discrimination under different acoustic distortions of vocalizations. To achieve this, the auditory system is thought to build a representation of vocalizations that is invariant to their basic acoustic transformations. The mechanism by which neuronal populations create such an invariant representation within the auditory cortex is only beginning to be understood. We recorded the responses of populations of neurons in the primary and nonprimary auditory cortex of rats to original and acoustically distorted vocalizations. We found that populations of neurons in the nonprimary auditory cortex exhibited greater invariance in encoding vocalizations over acoustic transformations than neuronal populations in the primary auditory cortex. These findings are consistent with the hypothesis that invariant representations are created gradually through hierarchical transformation within the auditory pathway.