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The purpose of this paper is to demonstrate the theoretical relationship between the layout of four‐sensor dynamic acoustic array tracking system and systematic observation accuracy, and provide an algorithm to determine the optimal arrangement of four‐sensor acoustic array and an indicator to evaluate acoustic array system measurement accuracy.

In the present paper, the measurement principle of the four‐sensor dynamic acoustic array tracking system is analyzed, and the system observation model and the conversion relationship between models are established. Subsequently, the optimization algorithm for the four‐sensor dynamic acoustic array is deduced, the theoretical optimal arrangement of the four‐sensor dynamic acoustic array tracking measurement system is obtained based on the optimal position dilution of precision function (PDOPF) of 2D target, and the static experimental study on sound‐source bearing estimation is designed. The theoretical results are compared with the experimental results of the present study.

The measurement accuracy of the four‐sensor dynamic acoustic array tracking system is largely dependent on the layout of the acoustic sensor. Theoretical studies and experimental results demonstrated that an optimal PDPOF can be used to analyze the rationality of the layout. It can also serve as an indicator for the layout of the four‐sensor dynamic acoustic array tracking system.

The PDOPF value is presented as an indicator for the evaluation of the four‐sensor dynamic acoustic array systematic observation accuracy based on theoretical analysis. The feasibility of the indicator and the rationality of the sensor layout in practical engineering application are verified through experimental studies on sound‐source bearing estimation. The higher the PDOPF value is, the lower the accuracy of the system will be.

To 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.

The 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.

PVAT 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.

When 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.

1. A pilot case study outlines the development and test of a variable acoustic prototype in a tertiary classroom

2. A method is adopted to measure acoustic conditions, using three under-researched Android applications

3. The benefits of PVAT are realised in its ability to vary RT by adjusting the prototypes’ sound absorption

4. By using PVAT in a single space, the recommended RTs for two room types outlined in the acoustic standard AS/NZS 2107:2016 can be satisfied

5. The improvements in acoustic comfort due to PVAT are statistically significant

A pilot case study outlines the development and test of a variable acoustic prototype in a tertiary classroom

A method is adopted to measure acoustic conditions, using three under-researched Android applications

The benefits of PVAT are realised in its ability to vary RT by adjusting the prototypes’ sound absorption

By using PVAT in a single space, the recommended RTs for two room types outlined in the acoustic standard AS/NZS 2107:2016 can be satisfied

The improvements in acoustic comfort due to PVAT are statistically significant

The purpose of this paper is to present an acoustics-based method for measuring turbofan nozzle exhaust thrust, while assessing the potential of scaling the methods for in-flight measurements.

Although many methods proposed for achieving in-flight thrust measurements involve complicated, sensitive and expense instruments, an acoustics-based approach is discussed that greatly simplifies the technology development pathway to in-flight applications.

Results are provided for a minimum set of sensors applied in the exhaust of a research turbofan engine at Virginia Tech, showing the difference in acoustics-measured thrust and nozzle thrust found by integrating thermocouple and Kiel probe measurements to be less than 6 per cent at the maximum fan speed examined.

Measuring accurate thrust values in flight will prove immediately valuable for installed thrust validation and engine health monitoring. Acoustics-based methodologies are attractive because of the robustness and low cost of sensors and sources. The value of in-flight thrust measurements, along with the benefits of acoustic approaches, makes the current topic of great interest for further development.

This paper presents unique applications of a time-of-flight acoustic thrust sensor, while providing an original assessment of technological challenges involved with the progression of the technique for in-flight measurements.

It is currently difficult to measure temperature and pressure in harsh environments. Such measurements are limited by either the ability of the sensing element or the associated electrical wiring to withstand the operating environment. This is unfortunate as temperature and pressure are important measurands in various engineering structures as they provide critical information on the operating condition of the structure. Hence, there is a need to address this shortcoming. Such a sensor in place would enhance the operating efficiency thereby reducing the pollution burden and its impact on the environment. The purpose of this paper is to present theoretical and preliminary experimental results for a co‐integrated pressure and temperature sensor for harsh environments.

This work describes a co‐integrated pressure‐temperature wireless sensing scheme. The approach presented herein provides the possibility of measuring dynamic pressure and temperature within an enclosed volume using acoustic signals. Resonance tube physics is exploited for the temperature sensing. A microphone is used to obtain the acoustic signal whose frequency is a function of the temperature and the tube geometry.

The dynamic pressure is measured from the calibrated amplitude of the pressure wave signal measured by the microphone. The temperature can be measured through the shift of the standing wave frequency with a resolution of <1°C. The resonance tube can be fabricated using any material that resists harsh environments. The geometry of the tube can be tailored for any specific frequency range, as the application warrants. Also, this provides a means for accurate temperature compensation of pressure sensor data from high temperature environments. A Matlab/Simulink model is developed and presented for the acquisition of acoustic signals through the wall of an enclosed volume. For these applications the standing wave signal transmitted through the enclosure wall becomes a function of the wall material and wall thickness. Preliminary experimental results are presented in which a DC fan is used for generating the dynamic pressure in a varying temperature environment.

The major issue is the separation of the noise from the signal. As various applications yield specific signal noise, the problem needs detailed data to be addressed.

Temperature and dynamic pressure could be recorded/monitored in very harsh environment conditions such as chemical reactors.

This work demonstrates the possibility of employing a co‐integrated acoustic sensing scheme in which both pressure and temperature are measured simultaneously with a sole sensor. The major advantage with acoustic sensing is the wireless transmission of data. This allows for non‐invasive measurement from within enclosed systems. Direct real‐time temperature compensation is possible that does not require any compensation circuitry. Hence, pressure and temperature data may be obtained from caustic operating environments whose access is otherwise not feasible.

As oral communication in higher education is vital, good classroom acoustics is needed to pass the verbal message to university students. Non-auditory factors such as academic language, a non-native educational context and a diversity of acoustic settings in different types of classrooms affect speech understanding and performance of students. The purpose of this study is to find out whether the acoustic properties of the higher educational teaching contexts meet the recommended reference levels.

Background noise levels and the Speech Transmission Index (STI) were assessed in 45 unoccupied university classrooms (15 lecture halls, 16 regular classrooms and 14 skills laboratories).

The findings of this study indicate that 41 classrooms surpassed the maximum reference level for background noise of 35 dB(A) and 17 exceeded the reference level of 40 dB(A). At five-meter distance facing the speaker, six classrooms indicated excellent speech intelligibility, while at more representative listening positions, none of the classrooms indicated excellent speech intelligibility. As the acoustic characteristics in a majority of the classrooms exceeded the available reference levels, speech intelligibility was likely to be insufficient.

This study seeks to assess the acoustics in academic classrooms against the available acoustic reference levels. Non-acoustic factors, such as academic language complexity and (non-)nativeness of the students and teaching staff, put higher cognitive demands upon listeners in higher education and need to be taken into account when using them in daily practice for regular students and students with language/hearing disabilities in particular.

The Reflective Middleware for Acoustic Management (ReM-AM), based on the Middleware for Cloud Learning Environments (AmICL), aims to improve the interaction between users and agents in a Smart Environment (SE) using acoustic services, in order to consider the unpredictable situations due to the sounds and vibrations. The middleware allows observing, analyzing, modifying and interacting in every state of a SE from the acoustics. This work details an extension of the ReM-AM using the ontology-driven architecture (ODA) paradigm for acoustic management.

This work details an extension of the ReM-AM using the ontology-driven architecture (ODA) paradigm for acoustic management. In this paper are defined the different domains of knowledge required for the management of the sounds in SEs, which are modeled using ontologies.

This work proposes an acoustics and sound ontology, a service-oriented architecture (SOA) ontology, and a data analytics and autonomic computing ontology, which work together. Finally, the paper presents three case studies in the context of smart workplace (SWP), ambient-assisted living (AAL) and Smart Cities (SC).

Future works will be based on the development of algorithms for classification and analysis of sound events, to help with emotion recognition not only from speech but also from random and separate sound events. Also, other works will be about the definition of the implementation requirements, and the definition of the real context modeling requirements to develop a real prototype.

In the case studies is possible to observe the flexibility that the ReM-AM middleware based on the ODA paradigm has by being aware of different contexts and acquire information of each, using this information to adapt itself to the environment and improve it using the autonomic cycles. To achieve this, the middleware integrates the classes and relations in its ontologies naturally in the autonomic cycles.

The main contribution of this work is the description of the ontologies required for future works about acoustic management in SE, considering that what has been studied by other works is the utilization of ontologies for sound event recognition but not have been expanded like knowledge source in an SE middleware. Specifically, this paper presents the theoretical framework of this work composed of the AmICL middleware, ReM-AM middleware and the ODA paradigm.

Ultrasound is a well-established technology in medical science, though many of the conventional measurement systems (hydrophones and radiation force balances [RFBs]) often lack accuracy and tend to be expensive. This is a significant problem where sensors must be considered to be “disposable” because they inevitably come into contact with biological fluids and expense increases dramatically in cases where a large number of sensors in array form are required. This is inevitably the case where ultrasound is to be used for the in vitro growth stimulation of a large plurality of biological samples in tissue engineering. Traditionally only a single excitation frequency is used (typically 1.5 MHz), but future research demands a larger choice of wavelengths for which a single broadband measurement transducer is desirable. Furthermore, because of implementation conditions there can also be large discrepancies between measurements. The purpose of this paper deals with a very cost-effective alternative to expensive RFBs and hydrophones.

Utilization of cost-effective piezoelectric elements as broadband sensors.

Very effective results with equivalent (if not better) accuracy than expensive alternatives.

This paper concentrates on how very cost-effective piezoelectric ultrasound transducers can be implemented as sensors for ultrasound power measurements with accuracy as good, if not better than those achievable using radiation force balances or hydrophones.

This study aims to examine activity-related sound levels and pupils’ perceptions of the acoustic environment in two classrooms, one of which was a traditional classroom (Reference classroom, reverberation time (RT) 0.54 s) and the other a refurbished classroom (Demo classroom, RT 0.32 s).

Three types of data were gathered: room acoustic measurements, activity sound levels during different activities and pupils’ subjective experience concerning factors related to acoustics. Pupils, 10–11 years old (N = 34), estimated their subjective experience in general and after four test lessons. Teachers planned the test lessons to have four different lesson types: quiet work, one-person speaking, group work and activity-based work. The sound levels of activities were measured during the test lessons.

The activity sound levels were 2–13 dB L_Aeq lower in the Demo classroom than in the Reference classroom, depending on lesson type. Pupils were less annoyed by noise in the Demo than in the Reference classroom. Pupils’ speech was the most annoying sound source. More pupils were annoyed by it in the Reference classroom (65%) than in the Demo classroom (15%). Hearing the teacher while not seeing her face, concentrating on teaching and sitting in one’s place were estimated easier in the Demo classroom than in the Reference classroom.

This study offers a new approach using test lessons for studying activity sounds in schools. Activity sounds and their annoyance can be significantly diminished by classroom refurbishments.

There are structural elements on the aircraft that may be exposed to high-intensity sound levels. One of them is an air inlet duct of the jet engine. To prepare data for the air duct damage tolerance analysis, flat panels were tested under acoustic loading. The paper aims to discuss this issue.

The acoustic fatigue test equipment for grazing wave’s incidence was designed based on the FE analyses. Flat composite panels were designed and manufactured using the Hexply 8552/AGP193-PW prepreg with the simulation of production imperfections or operational damage. The dynamic behaviour of panels has been tested using three regimes of acoustic loading: white noise spectrum, engine noise spectrum and discrete harmonic frequencies. The panel deflection was monitored along its longitudinal axis, and the ultrasonic NDT instruments were used for the monitoring of relevant delamination increments. The FE model of the panel was created in Abaqus to study panel dynamic characteristics.

No delamination progress was observed by NDT testing even if dynamic characteristics, especially modal frequency, of the panel changed during the fatigue test. Rayleigh damping coefficients were evaluated for their use in FE models. Significant differences were found between the measured and computed panel deflection curves near the edge of the panel.

The research results underscored the signification of the FE model boundary conditions and the element type selections when the panel works like a membrane rather than a plate because of their low bending stiffness.

The purpose of this paper is to report an investigation into acoustic emission (AE) characteristics of the corrosion situation of the bottom of a large storage tank.

Guard sensors were applied in on‐line AE inspection of a tank bottom, and the AE signal characteristics of the corrosion areas of tank bottom were analyzed. The AE test results were compared with those from an internal tank internal test.

It was observed that guard sensors could shield effectively a large proportion of the extraneous noise signals inside the tank. The characteristics of AE signals from different types of corrosion were significantly different. A comparison of AE test results and tank internal inspection data showed a good agreement.

Characteristic AE signals from different types of corrosion were obtained for the first time, which assisted in the identification of the tank bottom corrosion situation.