Acoustic Prototype Research Articles

Super-resolution acoustic displacement metrology through topological pairs in orbital meta-atoms

The precise measurement of minute displacements using light is a common practice in modern science and technology. The utilization of sound for precision displacement metrology remains scarce due to the diffraction limit of half-wavelength, while it holds crucial applications in some specific scenarios, such as underwater environments, biological tissues, and complex machinery components. Here, we propose an approach to super-resolution acoustic displacement metrology by introducing the concept of topological pairs in orbital meta-atoms, drawing inspiration from the analogy of Cooper pairs observed in spinful electrons. The topological pairs are conjugately formed to create two distinct pathways in mode space that enable robust generation of interference. This allows the realization of acoustic analogue of Malus’s law and thereby enhances the resolution of displacement measurements. By incorporating a spiral twist configuration in orbital meta-atoms, we demonstrate the first acoustic prototype of a physical micrometer tailored for micron-scale displacement metrology. We observe experimentally a displacement resolving power of 1.2 μm at an audible frequency of 3.43 kHz, approximately 1/105 of the sound wavelength of 100 mm. Our work implies a new paradigm for precise displacement metrology within classical wave physics and lays the foundation for diverse acoustic applications.

Passive variable acoustic technology for classroom reverberation time: a case study

PurposeTo maximise acoustic comfort in a classroom, the acoustic conditions of the space should be variable. So, the optimal acoustic state also changes when the classroom changes from a study environment into a lecture environment. Passive Variable Acoustic Technology (PVAT) alters a room’s Reverberation Time (RT) by changing the total sound absorption in a room. The purpose of this paper is to evaluate the improvements to classroom acoustic comfort when using PVAT.Design/methodology/approachThe study is conducted in an existing tertiary classroom at Auckland University of Technology, New Zealand. The PVAT is prototyped, and the RTs are measured according to international standards before and after classroom installation. The acoustic measurement method used is a cost-effective application tool where pre- and post-conditions are of primary concern.FindingsPVAT is found to offer statistically significant improvements in RT, but the key benefits are realised in its’ ability to vary RT for different classroom situations. It is predicted that the RT recommendations for two room types outlined in the acoustic standard AS/NZS 2107:2016 are satisfied when using PVAT in a single classroom space. By optimising RT, the acoustic comfort during both study and lecture is significantly improved.Originality/valueWhen PVAT is combined with an intelligent system – Intelligent Passive Room Acoustic Technology (IPRAT) – it can detect sound waves in real time to identify the optimal RT. This paper details a pilot case study that works towards quantifying the benefits of IPRAT, by prototyping and testing the PVAT component of the system.Highlights A pilot case study outlines the development and test of a variable acoustic prototype in a tertiary classroomA method is adopted to measure acoustic conditions, using three under-researched Android applicationsThe benefits of PVAT are realised in its ability to vary RT by adjusting the prototypes’ sound absorptionBy using PVAT in a single space, the recommended RTs for two room types outlined in the acoustic standard AS/NZS 2107:2016 can be satisfiedThe improvements in acoustic comfort due to PVAT are statistically significant

Acoustic Module for Direction Finding of Small Aircraft

Introduction. The studied problem is relevant due to the growing use of unmanned small aircraft for mobile services of the mail and goods delivery, surveillance and security. At the same time, the danger of their use in events/campaigns, which pose a threat to both public and private interests, is increasing. Principally different devices are applied for surveillance; each type has its advantages and disadvantages. Passive acoustic surveillance tools provide stealth observation, but have a small detection range. It is possible to increase detection distance by improving the receiving microphones module design and developingeffective monitoring and localization algorithms. Theoretical Results. The paper presents the design of an acoustic module in the form of a tetrahedron with microphones located on its vertices. It is proposed to scan the space by angular coordinates using algorithms to generate a controlled power characteristic or controlled correlation characteristic. The theoretical justification of scanning algorithms, the results of the calculation of directivity characteristics and estimates of the error in determining the angular coordinates for each method are provided. Laboratory studies were conducted on direction finding of a noise source by the acoustic module prototype. Despite of reverberation in the room, it was possible to verify the theoretical results and confirm the advantage of the algorithm for the correlation formation of directivity. Conclusions. The results of the work can be used to create acoustic direction finders and systems for localizing noise objects. The proposed algorithm of controlled correlation characteristic can be used in monitoring tools to assess the acoustic characteristics of premises, for example, to experimentally determine the location and estimate sound absorption of enclosing constructions/the obstacles, to localize breaches in sound isolation.

Proper Orthogonal Decomposition Analysis and Dispersion Characteristics of Resonant Acoustic Flow

The investigation on the flow field and mixing characteristics of resonant sound mixing is of great significance for the dispersion mixing of superfine materials. In order to simulate the flow field and dispersion characteristics of resonant acoustic mixing, a gas-liquid-solid three-phase flow model based on the coupled level-set and volume-of-fluid (CLSVOF) and discrete particle model (DPM) was established. The CLSVOF model solves the gas-liquid interface, and the DPM model tracks the particle position. Then, the particle image velocimetry (PIV) experiment was performed using a self-made resonance acoustic hybrid prototype under different oscillation accelerations, and the radial velocity distribution between the experiment and simulation was compared. Finally, the proper orthogonal decomposition (POD) is used to decompose the flow field under different oscillation accelerations and fill levels, and the energy distribution law and the energy structure of different scales are extracted. The results show that the energy of the instantaneous flow field of the resonant sound is mainly concentrated in the low-order mode, and a close relationship was revealed between the energy distribution law and dispersion behavior of particles. The larger the small-scale coherent structures distribute, the more energy it has and the more favorable it is for fast and uniform dispersion.

Theoretical investigation and prototype design for non-parallel squeeze film movement platform driven by standing waves

Abstract In order to realize contactless levitation and movement of precision components, a new kind of acoustic prototype driven by standing waves utilizing reverse hydrodynamic effects of non-parallel squeeze film was proposed in this paper. Its mechanism of movement and levitation was revealed by the viscous fluid mechanics and dynamic lubrication theory. It is amazing that the reverse hydrodynamic effects made the levitated plate move along the opposite direction of gravitational tangential component, which was proved in the experiments. The bearing and pushing capacity is predicted by numerical calculation of Reynolds equation and a CFX model. A dimensionless parameter 'voltage difference ratio' was proposed to evaluate the deflection angle of a non-parallel squeeze film, which can guide the prototype design.

Prototipo acústico adaptable. Para espacios multifuncionales

This paper present the first stage of research “Adaptative Acoustic Prototype –for multifunctional spaces–”, developed at the School of Architecture of de University of Santiago de Chile. The main has been to design and build a device of articulated geometry has been developed that allows calibrate the acoustics of the space, depending on users reception needs. The theoretical basis of the proposal is revides from the concept of liquid architecture, which in its foundation seeks to incorporate dynamic dimension of time in material condition of spaces. We also examine the variable acoustic term, which deals technically with the verality of sound event in a display of active or passive techniques. Then the research through design metodology is presented, based on the model proposed by Lucien Blessing, which formulates a process from definition of the research criteria until the design and the formal concretion in model construction. Finally, we present the validation design parameters that aim at the continuation of development in a second stage. The objetive will be to model optimize and to improve the transformations of material, spatial and temporal acoustic enviroment, as it has been proposed.

Performance Evaluation of 3D-Position Estimation Systems

Applications that are based on indoor location awareness have different requirements with regard to the accuracy of the estimated positions, the measurement cycle time, and the (end-to-end) delay between the start of a measurement and the availability of the position result. Moreover, the energy consumption of the mobile tags is a key parameter for the selection of an appropriate system. In this paper, we present the results of a series of real-time 3D-position measurements carried out with three respective systems. The two commercial systems, DecaWave DW1000 and Time Domain P410, are based on radio-frequency measurements, while an acoustic prototype system employs time-of-flight measurements based on audible signals. The systems were tested in stationary as well as in dynamic scenarios. Our results provide the accuracies and precisions of the individual systems, the position update rates, and the end-to-end delays. In additional measurements, we determined the individual tag power consumptions and calculated a figure of merit giving the energy consumption per position measurement.

Diseño y desarrollo de nuevos materiales textiles para el aislamiento y acondicionamiento acústico

El presente artículo trata el problema de ¿Cómo disminuir la emisión de ruido en un determinado ambiente? Para responder a esta interrogante, se han considerado dos materiales absorbentes: la lana de vidrio y la napa textil, los cuales, mediante la construcción de un prototipo de panel acústico, se sometieron a un experimento siguiendo los lineamientos de la norma UNE-EN 20354, permitiendo aislamientos acústicos entre 20 dB a 30 dB para intensidades de sonidos entre 100 a 120 dB.

Sensory Navigation Device for Blind People

This paper presents a new Electronic Travel Aid (ETA) ‘Acoustic Prototype’ which is especially suited to facilitate the navigation of visually impaired users. The device consists of a set of 3-Dimensional Complementary Metal Oxide Semiconductor (3-D CMOS) image sensors based on the three-dimensional integration and Complementary Metal-Oxide Semiconductor (CMOS) processing techniques implemented into a pair of glasses, stereo headphones as well as a Field-Programmable Gate Array (FPGA) used as processing unit. The device is intended to be used as a complementary device to navigation through both open known and unknown environments. The FPGA and the 3D-CMOS image sensor electronics control object detection. Distance measurement is achieved by using chip-integrated technology based on the Multiple Short Time Integration method. The processed information of the object distance is presented to the user via acoustic sounds through stereophonic headphones. The user interprets the information as an acoustic image of the surrounding environment. The Acoustic Prototype transforms the surface of the objects of the real environment into acoustical sounds. The method used is similar to a bat's acoustic orientation. Having good hearing ability, with few weeks training the users are able to perceive not only the presence of an object but also the object form (that is, if the object is round, if it has corners, if it is a car or a box, if it is a cardboard object or if it is an iron or cement object, a tree, a person, a static or moving object). The information is continuously delivered to the user in a few nanoseconds until the device is shut down, helping the end user to perceive the information in real time.

Acoustic search for high-energy neutrinos in the Lake Baikal: Results and plans

We report the present status and perspectives of the feasibility study to detect cosmic neutrinos acoustically in the Lake Baikal. The results of background studies are presented. It was shown that most of the detected neutrino-like pulses come from the lake surface. This fact has been used in the project of an acoustic prototype detector that consists of compact Acoustic Sensor Modules with 4-channel antennas each, arranged above the Baikal Neutrino Telescope at shallow depths and “listening” the deep-water layers of the lake.

A new capnograph based on an electro acoustic sensor

End tidal carbon dioxide measurements with an electro acoustic capnograph prototype have been demonstrated. The aim of this study was to verify that it is possible to obtain an adequate capnogram using the prototype and to investigate the influence of ambient temperature and humidity variations. By simultaneous measurements with a reference capnograph, on subjects performing exercise, hypo- and hyperventilation, P(ET)CO(2) readings from the reference were compared with the output signal from the prototype. The capnogram from the prototype correlated well with the reference in terms of breath time. The first parts of the expiration and inspiration phases were steeper for the reference than the prototype. The output signal from the prototype correlated well with the reference P(ET)CO(2) readings with a correlation coefficient of 0.93 at varied temperature and relative humidity.

Characterisation of an airborne sound source for use in a virtual acoustic prototype

An approach is outlined suitable for constructing ‘virtual acoustic prototypes’ of machines. Here, the machine is ‘sub-structured’ into: active components (vibro-acoustic sources), and frame (the remaining passive parts of the machine). The approach is validated using the illustrative example of an electric motor installed in a machine frame. The motor is characterised by a line of four monopoles on its axis, the complex source strengths for which are obtained from the measured anechoic sound field around the motor using an inverse method. A singular value decomposition is carried out both to aid the solution and to shed light on the dominant mechanisms. A set of compatible transfer functions of a machine frame is then measured using a reciprocal technique. The sound power of the assembled machine is then predicted using a ‘virtual prototype’ approach of combining motor and frame data in the computer. Reasonable agreement is obtained with measurements made on a real prototype, although the agreement was limited at least in part by difficulties in repeating the same operating conditions for the motor. A simplified characterisation, using a single monopole, and with improved motor control produced excellent agreement.

Reduction of search space in speech recognition using phone boundaries and phone ranking

A method for estimating the probability of phone boundaries and the accuracy of the acoustic modelling in reducing a search-space in a speech recognition system. The accuracy of the acoustic modelling is quantified by the rank of the correct phone. The system includes a microphone for converting an utterance into an electrical signal, which is processed by an acoustic processor and label match which finds the best-matched acoustic label prototype. A probability distribution on phone boundaries is produced for every time frame using a first decision tree. These probabilities are compared to a threshold and some time frames are identified as boundaries between phones. An acoustic score is computed for all phones between every given pair of hypothesized boundaries, and the phones are ranked on the basis of this score. A second decision tree is traversed for every time frame to obtain the worst case rank of the correct phone at that time, and a short list of allowed phones is made for every time frame. A fast acoustic word match processor matches the label string from the acoustic processor to produce an utterance signal which includes at least one word. From recognition candidates produced by the fast acoustic match and the language model, the detailed acoustic match matches the label string from the acoustic processor against acoustic word models and outputs a word string corresponding to an utterance.

Speech coding apparatus having acoustic prototype vectors generated by tying to elementary models and clustering around reference vectors

A speech coding apparatus in which measured acoustic feature vectors are each represented by the best matched prototype vector. The prototype vectors are generated by storing a model of a training script comprising a series of elementary models. The value of at least one feature of a training utterance of the training script is measured over each of a series of successive time intervals to produce a series of training feature vectors. A first set of training feature vectors corresponding to a first elementary model in the training script is identified. The feature value of each training feature vector signal in the first set is compared to the parameter value of a first reference vector signal to obtain a first closeness score, and is compared to the parameter value of a second reference vector to obtain a second closeness score for each training feature vector. For each training feature vector in the first set, the first closeness score is compared with the second closeness score to obtain a reference match score. A first subset contains those training feature vectors in the first set having reference match scores better than a threshold Q, and a second subset contains those having reference match scores less than the threshold Q. One or more partition values are generated for a first prototype vector frown the first subset of training feature vectors, and one or more additional partition values are generated for the first prototype vector from the second subset of training feature vectors.

Speech recognition apparatus having a speech coder outputting acoustic prototype ranks

A speech coding and speech recognition apparatus. The value of at least one feature of an utterance is measured over each of a series of successive time intervals to produce a series of feature vector signals. The closeness of the feature value of each feature vector signal to the parameter value of each of a set of prototype vector signals is determined to obtain prototype match scores for each vector signal and each prototype vector signal. For each feature vector signal, first-rank and second-rank scores are associated with the prototype vector signals having the best and second best prototype match scores, respectively. For each feature vector signal, at least the identification value and the rank score of the first-ranked and second-ranked prototype vector signals are output as a coded utterance representation signal of the feature vector signal, to produce a series of coded utterance representation signals. For each of a plurality of speech units, a probabilistic model has a plurality of model outputs, and output probabilities for each model output. Each model output comprises the identification value of a prototype vector and a rank score. For each speech unit, a match score comprises an estimate of the probability that the probabilistic model of the speech unit would output a series of model outputs matching a reference series comprising the identification value and rank score of at least one prototype vector from each coded utterance representation signal in the series of coded utterance representation signals.

Adaptation of acoustic prototype vectors in a speech recognition system

In a speech recognition system, the prior parameters of acoustic prototype vectors are adapted to a new speaker to obtain posterior parameters by having the speaker utter a set of adaptation words. The prior parameters of an acoustic prototype vector are adapted by a weighted sum of displacement vectors obtained from the adaptation utterances. Each displacement vector is associated with one segment of an uttered adaptation word. Each displacement vector represents the distance between the associated segment of the adaptation utterance and the model corresponding to that segment. Each displacement vector is weighted by the strength of the relationship of the acoustic prototype vector to the word segment model corresponding to the displacement vector.