Pantheon habitat made from regolith, with a focusing solar reflector.

We describe a polar Moon base habitat using direct solar energy for construction, food production and atmospheric revitalization. With a growing area as large as 2000 m2, it could provide for 40 or more people. The habitat is built like the ancient Roman Pantheon, a stone structure with a top circular oculus, bringing in focused sunlight that is spread out to crops below. The conical, corbelled structure is built from cast regolith blocks, held in compression despite the large internal atmospheric pressure by a regolith overlayer 20-30 m thick. It is sealed on the inside against leaks with thin plastic. A solar mirror concentrator used initially to cast the building blocks is later used to illuminate the habitat through a small pressure window at the oculus. Three years of robotic preparation of the building blocks does not seem excessive for a habitat which can be expected to last for millennia, as has the Treasury of Atreus made by similar dry-stone construction. One goal of returning to the Moon is to demonstrate the practicality of long-term human habitation off the Earth. The off-axis, paraboloidal reflecting mirror is rotated about the vertical polar axis in order to direct horizontal sunlight downward to a focus. In this way, the heavy materials needed from Earth to build and power the habitat are largely limited to the solar concentrator and regolith moving and moulding equipment. By illuminating with a reflector rather than with electricity, the solar collection area is 20 times smaller than would be needed for PV cells. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades'.

Eurasian Tunnel Project: the first saturation dives during compressed-air work in Turkey.

The Eurasian Tunnel is a 5.64-km crossroad tunnel that connects Europe and Asia. Located under the seabed for the first time, 3.34 km of the tunnel that crosses the Bosphorus was built by advanced tunneling techniques. An exclusively designed tunnel boring machine (TBM), which has an operating pressure of 11 bars and a diameter of 13.7 meters was used for boring the seabed tunnel. The deepest point was 106 meters below sea level. One bounce diving period and seven saturation diving periods were needed for the repair and maintenance of the TBM during the project. Total time spent under pressure was 5,763 hours. A saturation decompression chamber for four divers was used for the saturation interventions, and divers breathed trimix at storage and excursion depths. The longest saturation run was the second, with storage at 10 bars and excursions to 10.4 bars. Twenty-three professional divers who were all experienced in compressed-air work were assigned to work on the project. Four dive physicians provided medical support, which included screening of divers before and during the hyperbaric interventions as well as on-site supervision. There were no diving-related accidents. A minor hand trauma, an external otitis and occasional insomnia were non-diving-related health issues that occurred during saturation and bounce diving. To our knowledge, the Eurasian Tunnel was the first project to perform TBM repair operations at such depths under the seabed and the first saturation diving in Turkey. In this report, we aimed to share our experiences of hyperbaric medical consulting in support of this type of tunneling project.

Response of green roof performance to multiple hydrologic and design variables: a laboratory investigation.

Multiple factors affect green roof performance and their effects might vary at different stages of operation. This paper aimed to link green roof performance to hydrologic variables (antecedent moisture condition (AMC) and rainfall intensity) and design variables (growing medium (GM) type and depth) under multiple dimensions at the early stage of operation using laboratory experiment data. The results showed that the AMC is the most influential factor of hydrologic performance, whereas the GM type appeared to primarily affect the nutrient levels of the outflow. The significant main effects of other variables and interaction effects between two variables point to challenges in green roof design.

The influence of a green roof drainage layer on retention capacity and leakage quality.

The aim of the research was to determine the influence of the substrate and different drainage materials on retention capacity and runoff water quality from three green roof containers. Phosphates were chosen as the water quality indicator based on their potential adverse impact on water quality in urban rainwater collectors. The field experiment was conducted at the Warsaw University of Life Sciences Water Center meteorological station in years 2013-2015. In terms of precipitation, the monitoring period covered a wet (+147.1 mm), average (+42.7 mm) and dry (- 66.3 mm) year. Leakage from the containers was recorded when the substrate moisture exceeded 20% and precipitation exceeded 3.5 mm/d for washed gravel, or 5.0 mm/d for a polypropylene mat and expanded clay. Phosphates were observed in leachates from all containers, with higher values observed in the second year of monitoring. As the result of this study, it can be concluded that the polypropylene mat and aggregates create different conditions for the formation of the leachate, in both volumes and its chemistry. The drainage layer made from a polypropylene mat is the most effective in terms of rainwater retention capacity and the resulting leachate quality.

Investigation of the sound generation mechanisms for in-duct orifice plates.

Sound generation due to an orifice plate in a hard-walled flow duct which is commonly used in air distribution systems (ADS) and flow meters is investigated. The aim is to provide an understanding of this noise generation mechanism based on measurements of the source pressure distribution over the orifice plate. A simple model based on Curle's acoustic analogy is described that relates the broadband in-duct sound field to the surface pressure cross spectrum on both sides of the orifice plate. This work describes careful measurements of the surface pressure cross spectrum over the orifice plate from which the surface pressure distribution and correlation length is deduced. This information is then used to predict the radiated in-duct sound field. Agreement within 3 dB between the predicted and directly measured sound fields is obtained, providing direct confirmation that the surface pressure fluctuations acting over the orifice plates are the main noise sources. Based on the developed model, the contributions to the sound field from different radial locations of the orifice plate are calculated. The surface pressure is shown to follow a U3.9 velocity scaling law and the area over which the surface sources are correlated follows a U1.8 velocity scaling law.

Occupational therapists' views on using a virtual reality interior design application within the pre-discharge home visit process.

BACKGROUND: A key role of Occupational Therapists (OTs) is to carry out pre-discharge home visits (PHV) and propose appropriate adaptations to the home environment in order to enable patients to function independently after hospital discharge. However, research shows that more than 50% of specialist equipment installed as part of home adaptations is not used by patients. A key reason for this is that decisions about home adaptations are often made without adequate collaboration and consultation with the patient. Consequently, there is an urgent need to seek out new and innovative uses of technology to facilitate patient/practitioner collaboration, engagement, and shared decision making in the PHV process. Virtual reality interior design applications (VRIDAs) primarily allow users to simulate the home environment and visualize changes prior to implementing them. Customized VRIDAs, which also model specialist occupational therapy equipment, could become a valuable tool to facilitate improved patient/practitioner collaboration, if developed effectively and integrated into the PHV process. OBJECTIVE: The intent of the study was to explore the perceptions of OTs with regard to using VRIDAs as an assistive tool within the PHV process. METHODS: Task-oriented interactive usability sessions, utilizing the think-aloud protocol and subsequent semi-structured interviews were carried out with seven OTs who possessed significant experience across a range of clinical settings. Template analysis was carried out on the think-aloud and interview data. Analysis was both inductive and driven by theory, centering around the parameters that impact upon the acceptance, adoption, and use of this technology in practice as indicated by the Technology Acceptance Model (TAM). RESULTS: OTs' perceptions were identified relating to three core themes: (1) perceived usefulness (PU), (2) perceived ease of use (PEoU), and (3) actual use (AU). Regarding PU, OTs believed VRIDAs had promising potential to increase understanding, enrich communication and patient involvement, and improve patient/practitioner shared understanding. However, it was unlikely that VRIDAs would be suitable for use with cognitively impaired patients. For PEoU, all OTs were able to use the software and complete the tasks successfully; however, participants noted numerous specialist equipment items that could be added to the furniture library. AU perceptions were positive regarding use of the application across a range of clinical settings including children/young adults, long-term conditions, neurology, older adults, and social services. However, some "fine tuning" may be necessary if the application is to be optimally used in practice. CONCLUSIONS: Participants perceived the use of VRIDAs in practice would enhance levels of patient/practitioner collaboration and provide a much needed mechanism via which patients are empowered to become more equal partners in decisions made about their care. Further research is needed to explore patient perceptions of VRIDAs, to make necessary customizations accordingly, and to explore deployment of the application in a collaborative patient/practitioner-based context.

Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures.

Dodecahedron sound sources are widely used for acoustical measurement purposes as they produce a good approximation of omnidirectional radiation. Evidence shows that such an assumption is acceptable only in the low-frequency range (namely below 1 kHz), while at higher frequencies sound radiation is far from being uniform. In order to improve the accuracy of acoustical measurements obtained from dodecahedron sources, international standard ISO 3382 suggests an averaging of results after a source rotation. This paper investigates the effects of such rotations, both in terms of variations in acoustical parameters and spatial distribution of sound reflections. Taking advantage of a spherical microphone array, the different reflection patterns were mapped as a function of source rotation, showing that some reflections may be considerably attenuated for different aiming directions. This paper investigates the concept of averaging results while changing rotation angles and the minimum number of rotations required to improve the accuracy of the average value. Results show that averages of three measurements carried out at 30° angular steps are closer to actual values and show much less fluctuation. In addition, an averaging of the directional intensity components of the selected responses stabilizes the spatial distribution of the reflections.

On the in situ impedance measurement with pu-probes--simulation of the measurement setup.

High-quality numerical simulations in room acoustics require a detailed knowledge of the acoustic reflection characteristics of the materials in the room, in order to realistically model the interferences between multiple sound reflections at the room boundaries. While different standardized measurement methods exist for the determination of the absorption coefficient and reflection factor these methods can generally not be applied in situ. Thus time-consuming laboratory measurements and the supply of material samples are required. Driven by the obvious demand for a reliable in situ measurement technique, a pu-probe based method has emerged during the last years, which derives the reflection factor based on the simultaneous measurement of sound pressure and velocity. However, previous investigations of the setup and publications by other authors have shown that the measurement results are affected by various uncertainty factors. The present study aims at the identification, separation, and quantitative assessment of the uncertainty factors related to reflection and diffraction effects at the loudspeaker, sensor, and the absorber geometry. Therefore, a purely simulative approach will be used that replicates the actual measurement situation in every detail, including the geometries of sensor, loudspeaker, and absorber. The simulation setup is validated by measurements and is used to systematically separate the different uncertainty factors.

Uncertainties in predicting structure-borne sound power input into buildings.

There has been a steady development of methods of measurement and prediction of structure-borne noise in buildings, particularly over the last two decades. In proposing and evaluating these methods, a major consideration has been the likely trade-off between accuracy and simplicity. Structure-borne sound transmission is a more complicated process than airborne sound transmission, but practitioners seek methods of prediction for the former, which are as straightforward as for the latter. In this paper a description is given of a study of multi-contact sources in buildings. The study concentrates on measurement and calculation procedures for sources and calculation procedures for receiver structures, particularly lightweight building elements. Although the study is not exhaustive, the findings point to the limitations of simplified methods, specifically the uncertainties likely as a result of reducing the data sets and computational effort, and the discrepancies resulting from simplifying assumptions.

Room acoustics analysis using circular arrays: an experimental study based on sound field plane-wave decomposition.

Plane-wave decomposition (PWD) methods using microphone arrays have been shown to be a very useful tool within the applied acoustics community for their multiple applications in room acoustics analysis and synthesis. While many theoretical aspects of PWD have been previously addressed in the literature, the practical advantages of the PWD method to assess the acoustic behavior of real rooms have been barely explored so far. In this paper, the PWD method is employed to analyze the sound field inside a selected set of real rooms having a well-defined purpose. To this end, a circular microphone array is used to capture and process a number of impulse responses at different spatial positions, providing angle-dependent data for both direct and reflected wavefronts. The detection of reflected plane waves is performed by means of image processing techniques applied over the raw array response data and over the PWD data, showing the usefulness of image-processing-based methods for room acoustics analysis.

Modal density and modal distribution of bending wave vibration fields in ribbed plates.

Plates reinforced by ribs or joists are common elements in lightweight building structures, as well as in other engineering structures such as vehicles, ships, and aircraft. These structures, however, are often not well suited for simple structural acoustic prediction models such as statistical energy analysis. One reason is that the modal density is not uniformly distributed due to the spatial periodicity introduced by the ribs. This phenomenon is investigated in the present paper, using a modal model of a ribbed plate. The modal model uses the Fourier sine modes, and the coupling between the plate and ribs is incorporated using Hamilton's principle. This model is then used to investigate the modal density of the considered spatially periodic structure, and a grouping of the modes in different dominating directions is proposed. Suggestions are also given regarding how to proceed towards a simplified prediction model for ribbed plates.

Echo thresholds for reflections from acoustically diffusive architectural surfaces.

When sound reflects from an irregular architectural surface, it spreads spatially and temporally. Extensive research has been devoted to prediction and measurement of diffusion, but less has focused on its perceptual effects. This paper examines the effect of temporal diffusion on echo threshold. There are several notable differences between the waveform of a reflection identical to the direct sound and one from an architectural surface. The onset and offset are damped and the energy is spread in time; hence, the reflection response has a lower peak amplitude, and is decorrelated from the direct sound. The perceptual consequences of these differences are previously undocumented. Echo threshold tests are conducted with speech and music signals, using direct sound and a simulated reflection that is either identical to the direct sound or has various degrees of diffusion. Results indicate that for a speech signal, diffuse reflections are less easily detectable as a separate auditory event than specular reflections of the same total energy. For a music signal, no differences are observed between the echo thresholds for reflections with and without temporal diffusion. Additionally, echo thresholds are found to be shorter for speech than for music, and shorter for spatialized than for diotic presentation of signals.

Plenum window insertion loss in the presence of a line source--a scale model study.

The acoustical insertion losses of plenum windows installed on a building facade in the presence of a non-parallel line source are studied by using a 1:4 scaled down model in a semi-anechoic chamber in the present investigation. Two types of insertion losses, weighted by the normalized traffic noise spectrum (from the 100 Hz to 5000 Hz one-third octave bands), are defined with different references. The first one is for the case where the orientation of the building facade relative to the line source is fixed. The reference case is the opened window having the same orientation angle as the plenum window. The maximum and minimum insertion losses under this condition across the orientations tested are found to be around 14 dB and 5 dB, respectively. The other is the opposite situation where such orientation is allowed to change because of practical purposes and the reference for this condition is the opened window with its width span parallel to the line source. The corresponding maximum and minimum insertion losses are found to be around 18 dB and 8 dB, respectively. There are evidences showing that the lower order plenum acoustic modes are responsible for the relatively high low frequency insertion loss.

Design, construction, and evaluation of a 1:8 scale model binaural manikin.

Many experiments in architectural acoustics require presenting listeners with simulations of different rooms to compare. Acoustic scale modeling is a feasible means to create accurate simulations of many rooms at reasonable cost. A critical component in a scale model room simulation is a receiver that properly emulates a human receiver. For this purpose, a scale model artificial head has been constructed and tested. This paper presents the design and construction methods used, proper equalization procedures, and measurements of its response. A headphone listening experiment examining sound externalization with various reflection conditions is presented that demonstrates its use for psycho-acoustic testing.

High frequency acoustic transmission loss of perforated plates at normal incidence.

A study has been conducted on the transmission loss of perforated plates at normal incidence. The investigation includes a theoretical analysis of the problem with validation through experimentation. The experiments comprised microphone measurements of transmission loss for 11 perforated plates with variable thickness, hole size, and porosity. The theoretical model is based on planar wave propagation through a single contraction/expansion chamber with modifications to account for hole interaction effects. The resulting formula for transmission loss yields superior predictions over past theories for the range of properties investigated. Deviations between experimental measurements and theoretical predictions of transmission loss are less than about 1.5 dB for dimensionless hole diameter d/λ < 0.5. The accuracy of the model does not show a strong dependence on plate thickness-to-diameter ratio or porosity.

Speech interference and transmission on residential balconies with road traffic noise.

Balcony acoustic treatments can mitigate the effects of community road traffic noise. To further investigate, a theoretical study into the effects of balcony acoustic treatment combinations on speech interference and transmission is conducted for various street geometries. Nine different balcony types are investigated using a combined specular and diffuse reflection computer model. Diffusion in the model is calculated using the radiosity technique. The balcony types include a standard balcony with or without a ceiling and with various combinations of parapet, ceiling absorption and ceiling shield. A total of 70 balcony and street geometrical configurations are analyzed with each balcony type, resulting in 630 scenarios. In each scenario the reverberation time, speech interference level (SIL) and speech transmission index (STI) are calculated. These indicators are compared to determine trends based on the effects of propagation path, inclusion of opposite buildings and difference with a reference position outside the balcony. The results demonstrate trends in SIL and STI with different balcony types. It is found that an acoustically treated balcony reduces speech interference. A parapet provides the largest improvement, followed by absorption on the ceiling. The largest reductions in speech interference arise when a combination of balcony acoustic treatments are applied.

Impedance measurement of non-locally reactive samples and the influence of the assumption of local reaction.

In this paper, the measurement of the absorption coefficient of non-locally reactive sample layers of thickness d1 backed by a rigid wall is investigated. The investigation is carried out with the aid of real and theoretical experiments, which assume a monopole sound source radiating sound above an infinite non-locally reactive layer. A literature search revealed that the number of papers devoted to this matter is rather limited in comparison to those which address the measurement of locally reactive samples. Furthermore, the majority of papers published describe the use of two or more microphones whereas this paper focuses on the measurement with the pressure-particle velocity sensor (PU technique). For these reasons, the assumption that the sample is locally reactive is initially explored, so that the associated measurement errors can be quantified. Measurements in the impedance tube and in a semi-anechoic room are presented to validate the theoretical experiment. For samples with a high non-local reaction behavior, for which the measurement errors tend to be high, two different algorithms are proposed in order to minimize the associated errors.

Development of a hybrid wave based-transfer matrix model for sound transmission analysis.

In this paper, a hybrid wave based-transfer matrix model is presented that allows for the investigation of the sound transmission through finite multilayered structures placed between two reverberant rooms. The multilayered structure may consist of an arbitrary configuration of fluid, elastic, or poro-elastic layers. The field variables (structural displacements and sound pressures) are expanded in terms of structural and acoustic wave functions. The boundary and continuity conditions in the rooms determine the participation factors in the pressure expansions. The displacement of the multilayered structure is determined by the mechanical impedance matrix, which gives a relation between the pressures and transverse displacements at both sides of the structure. The elements of this matrix are calculated with the transfer matrix method. First, the hybrid model is numerically validated. Next a comparison is made with sound transmission loss measurements of a hollow brick wall and a sandwich panel. Finally, numerical simulations show the influence of structural damping, room dimensions and plate dimensions on the sound transmission loss of multilayered structures.

An optoacoustic point source for acoustic scale model measurements.

A massless acoustic source is proposed for scale model work. This source is generated by focusing a pulsed laser beam to rapidly heat the air at the focal point. This produces an expanding small plasma ball which generates a sonic impulse that may be used as an acoustic point source. Repeatability, frequency response, and directivity of the source were measured to show that it can serve as a massless point source. The impulse response of a rectangular space was determined using this type of source. A good match was found between the predicted and the measured impulse responses of the space.