Current Issue : October - December Volume : 2019 Issue Number : 4 Articles : 5 Articles
It has been hypothesized that objective assessment for building acoustic conditions\nonly may not always be representative of the usersâ?? perception in occupied\nindoor spaces. This study objectively and subjectively examined indoor\nacoustic condition in rooms within studentsâ?? hostels in Obafemi\nAwolowo University, Nigeria. The objective assessment considered the\nphysical measurement of sound pressure level in the rooms in relation to the\nroomsâ?? physical characteristics like window to external wall area and window\nto floor area ratios. The subjective assessment considered the occupantsâ?? perception\nof the acoustic condition in the rooms in relation to their personal\ncharacteristics like age, gender, body mass index, metabolic rate, and body\nskin area. The sound pressure level was measured in each of the randomly selected\n44 rooms at 15 minute intervals between 7 hours and 19 hours daily\nthrough a period of eight weeks. The measurement was done with High Accuracy\nDigital Sound Noise Level Data Loggers placed at work plane at the\ncentre of the rooms. The geometry of the rooms was documented through\nphysical measurements. All the occupants of the selected rooms as well as the\ntwo adjoining rooms, amounting to 696 respondents, were purposively selected\nto fill a questionnaire regarding activities carried out in the rooms, the\nfrequency of fenestration opening, the personal characteristics of the occupants\nand the roomsâ?? occupancy ratio. This study established a strong correlation\nbetween the objective and subjective assessments of the acoustic condition\nin the spaces. Moreover, out of all the occupantsâ?? personal characteristics\nconsidered, it was the age that has a relationship with the occupantsâ?? perception\nof the acoustic condition that is closest to significant level.The relationship\nbetween their perception and measured sound pressure level was slightly\nmore pronounced among the male gender than the female with correlation\ncoefficients of 0.115 and 0.096 respectively. This study concluded that none of\nthe considered occupantsâ?? personal characteristics can effectively predict their\nresponse to indoor acoustic condition in the spaces....
The acoustic analysis provides additional information on building tradition and related\nindoor practice that includes sound, thus deepening our understanding of architectural heritage.\nIn this paper, the sound field of the Orthodox medieval church Lazarica (Krusevac city, Serbia) is\nexamined. Lazarica is a representative of Morava architectural style, developed in the final period\nof the Serbian medieval state, when also the chanting art thrived, proving the importance of the\naural environment in Serbian churches. The church plan is a combination of a traditional inscribed\ncross and a triconch. After the in situ measurement of acoustic impulse response using EASERA\nsoftware, we built a computer model in the acoustic simulation software EASE and calibrated it\naccordingly. Following the parameters (reverberation time (T30), early decay time (EDT) and speech\ntransmission index (STI)), we examined the acoustic effect of the space occupancy, central dome\nand the iconostasis. In all the cases, no significant deviation between T30 and EDT parameter was\nobserved, which indicates uniform sound energy decay. Closing the dome with a flat ceiling did not\nshow any significant impact on T30, but it lowered speech intelligibility. The height of iconostasis\nshowed no significant influence on the acoustics of Lazarica church....
Photoacoustic (PA) tomography (PAT) has potential for use in brain imaging due to its rich\noptical contrast, high acoustic resolution in deep tissue, and good biosafety. However, the skull often\nposes challenges for transcranial brain imaging. The skull can cause severe distortion and attenuation\nof the phase and amplitude of PA waves, which leads to poor resolution, low contrast, and strong\nnoise in the images. In this study, we propose an image reconstruction method to recover the PA\nimage insider a skull-like scattering layer. This method reduces the scattering artifacts by combining\na correlation matrix filter and a time reversal operator. Both numerical simulations and PA imaging\nexperiments demonstrate that the proposed approach effectively improves the image quality with\nless speckle noise and better signal-to-noise ratio. The proposed method may improve the quality of\nPAT in a complex acoustic scattering environment, such as transcranial brain imaging....
Nowadays, more than half of the worldâ??s population lives in urban areas. Since this proportion is expected to keep rising, the\nsustainable development of cities is of paramount importance to guarantee the quality of life of their inhabitants. Environmental\nnoise is one of the main concerns that has to be addressed, due to its negative impact on the health of people. Different national\nand international noise directives and legislations have been defined during the past decades, which local authorities must comply\nwith involving noise mapping, action plans, policing, and public awareness, among others. To this aim, a recent change in the\nparadigm for environmental noise monitoring has been driven by the rise of Internet of Things technology within smart cities\nthrough the design and development of wireless acoustic sensor networks (WASNs). This work reviews the most relevant WASNbased\napproaches developed to date focused on environmental noise monitoring. The proposals have moved from networks\ncomposed of high-accuracy commercial devices to the those integrated by ad hoc low-cost acoustic sensors, sometimes designed\nas hybrid networks with low and high computational capacity nodes. After describing the main characteristics of recent WASNbased\nprojects, the paper also discusses several open challenges, such as the development of acoustic signal processing techniques\nto identify noise events, to allow the reliable and pervasive deployment of WASNs in urban areas together with some potential\nfuture applications....
The received signal strength (RSS) based target localization problem in underwater\nacoustic wireless sensor networks (UWSNs) is considered. Two cases with respect to target transmit\npower are considered. For the first case, under the assumption that the reference of the target\ntransmit power is known, we derive a novel weighted least squares (WLS) estimator by using\nan approximation to the RSS expressions, and then transform the originally non-convex problem\ninto a mixed semi-definite programming/second-order cone programming (SD/SOCP) problem for\nreaching an efficient solution. For the second case, there is no knowledge on the target transmit power,\nand we treat the reference power as an additional unknown parameter. In this case, we formulate a\nWLS estimator by using a further approximation, and present an iterative ML and mixed SD/SOCP\nalgorithm for solving the derived WLS problem. For both cases, we also derive the closed form\nexpressions of the Cramer-Rao Lower Bounds (CRLBs) on root mean square error (RMSE). Computer\nsimulation results show the superior performance of the proposed methods over the existing ones in\nthe underwater acoustic environment....
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