The effect of moisture content on sound absorption of expanded perlite plates

Cataloged from PDF version of article.Expanded perlite is a porous, lightweight, fire resistant and moisture retaining material with sound and thermal insulation properties. In this research, acoustical behaviour of plates made of expanded perlite was studied experimentally. Since these plates are used for sound absorption, the acoustical parameter selected for this study is "sound absorption coefficient". Preliminary experiments indicated that moisture reduced the sound absorption coefficient on plates and there is not much significant difference between the dry and 50% humid conditions. However, there is a significant difference in acoustical properties for the 50-95% humid conditions. Thus, this interval was studied in detail. A number of expanded perlite plates having different mixtures were prepared and tested. It was observed that, coating the expanded perlite particles with sodium silicate increased the moisture resistance. and the addition of mineral fibres into the mixtures increased the strength and sound absorption coefficient of the plates

Sound absorption coefficient changes of acoustical plates made of expanded perlite in moist environment

Expanded perlite is a porous, lightweight, fire resistant and moisture retaining material with sound and thermal insulation properties. In this research, acoustical behaviour of plates made of expanded perlite was studied experimentally. Since these plates are used for sound absorption the acoustical parameter selected for this study is "sound absorption coefficient". Preliminary experiments indicated that moisture reduced the sound absorption coefficient on plates and there is not much significant difference between the dry and 50% humid conditions. However, there is a significant difference in acoustical properties for the 50% 95% humid conditions. Thus, this interval was studied in detail. A number of expanded perlite plates having different mixtures were prepared and tested. It was observed that coating of expanded perlite particles with sodium silicate increased moisture resistance, and that the addition of mineral fibre into the mixtures increased the strength and sound absorption coefficient of the plates

An Overview and Assessment of Wireless Technologies and Co- existence of ZigBee, Bluetooth and Wi-Fi Devices

AbstractWi-Fi, ZigBee and Bluetooth wireless communication systems utilize the Industrial Scientific and Medical-(ISM) Band, which results in a high mutual interference between these technologies since they all these systems operate at the same or very close frequency bands. The interference problem increases with an in-device Co-existence (technologies existing on same device). This is primarily due to the characteristics of each technology such as access mechanism, frame structure, peak transmit power and frequency of operation. This work describes the interference between the Wi-Fi mostly as an aggressor on Bluetooth and ZigBee wireless networks. So the experimental analysis of the coexistence of these three technologies in an assumed home environment is studied especially when ZigBee is enabled for a Home Automation Network where there could be close proximity of Wi-Fi and Bluetooth devices such as PDAs and mobile phones. The obtained result shows that there is severe degradation on ZigBee and Bluetooth packet transmission of packets as well as re-transmission of ZigBee packets when Wi-Fi is operating

Relationships between measured levels and subjective ratings: A case study of the food-court area in CEPA shopping center, Ankara

Physical comfort requirements of users; such as, thermal, visual, and acoustic comfort, should be considered and studied in detail when planning and designing public spaces. However, there is not enough research on the relations between the acoustical parameters, and the acoustic comfort level of users in enclosed non-acoustic public spaces, which are directly connected with a central atrium. In such spaces, evaluation on auditory perception and noise annoyance should be performed in parallel with objective parametric measurements. The food-court area of CEPA Shopping Center, with a central atrium and a glass ceiling structure, in the capital city of Turkey, Ankara is chosen for the case. The aim of this study is to investigate the relationships between the users' subjective ratings of noise levels and the measured equivalent continuous sound pressure levels (Leq). In addition, the demographical differences and user profile variances, as well as the auditory perception classifications are investigated in this case space. The present acoustical indices are measured and then discussed by pointing out the architectural features of the case space, which are the central atrium, glass ceiling structure and the sound reflective material applications. The research methods include, noise measurements to obtain Leq and questionnaires to assess the subjective ratings and auditory perception of the users. This study mainly concentrates on the food-court space, which is within CEPA Shopping Center and displays the significant results regarding this space. These results show that Leq values vary by different day types (weekdays and weekends) and time of day, and the subjective ratings correlate well with these Leq variances. The most dominant sound perceived by the users was found to be the hum of voices. One other significant result implies that, subjective ratings of noise level becomes significant above 67 dBA and shows a sudden increase in the ratings. Furthermore, the time spent in the food-court area correlated significantly with noise annoyance ratings

The acoustical performance analysis of bilkent amphitheater: Proposal for acoustical renovation

The 4000 seat multi-purpose Bilkent Amphitheater is a semi-dosed amphitheater with a volume of 90,000 m3, designed to serve the University's and the city's educational and artistic activities. At the beginning, the amphitheater was designed only for open-air performances. Afterwards it was decided it would be roofed with a tensile membrane in order to protect the spectators from atmospheric effects. However, the covered amphitheater was turned into a resounding and a problematic place widi a reverberation time of more than 6 s. when the hall is unoccupied. Acoustical interventions were implemented, but these have not been sufficient in decreasing the number of problematic echoes and dead spots. This paper analyzes the hall by means of assessing the fundamental acoustical parameters for both speech and music. Parameters such as reverberation time, early decay time, clarify, definition, lateral fraction, strength and speech transmission index were calculated by the aid of ODEON Room Acoustics Program simulation software Version 6.01. It was observed that most of the parameters are out of the optimum range, and that the sound focused strongly in some locations. After further acoustical renovation of the hall, the distribution of sound became more homogenous as measures of most of the parameters fell into reasonable ranges. © 2006 University of Sydney. All rights reserved

The architectural colour design process: An evaluation of sequential media via semantic ratings

In recent studies, contextual situations of applied colours are compared to colours presented as samples or chips. Findings of such studies point out different results in terms of similarities or differences between the evaluations of isolated abstract colours and contextualized situations. Architectural and spatial contexts have their own characteristics regarding colouring criteria, so it is of great importance to examine the architectural spatial colouring process from this point of view. This study explores this process by investigating the consistency of semantic ratings of four sequential stages of the architectural colour design process, namely, colour chips samples, abstract compositions, perspective drawings and 3D models. The architectural context for the study was a simple interior space. Fifteen different colour schemes were applied on the four media representing the stages. Subjects rated the 15 sets against seven bipolar, five-step semantic differential scales. The scales consisted of harmonious-discord, pleasant-unpleasant, comfortableuncomfortable, spacious-confined, static-dynamic, exciting-calming and extroverted-introverted. Findings indicated that there are significant associations between the evaluations of the abstract compositions, the perspective drawings and the 3D models; however, the evaluations of colour chips are significantly different than the others. The medium effect observed mostly between abstract and contextualized media. Additionally, factor analysis showed that pleasantness, harmony, spaciousness and comfort are connected in the evaluations of contextual situations, while pleasantness and harmony differ from spaciousness and comfort in the evaluations of colour chips and abstract compositions. The factor of activity (arousal) (dynamism, excitement, and extroversion) stays the same for all four media. It is also found that different colour characteristics are determinative over different media. © 2010 Wiley Periodicals, Inc

The acoustical characteristics of the Kocatepe Mosque in Ankara, Turkey

This research investigates the acoustical characteristics of mosques of the classical Ottoman period and the contemporary period. Kocatepe Mosque, the major mosque in Ankara, Turkey, as a case from the contemporary era is a unique combination of 16th century Ottoman aesthetics and 20th century technology. Although previous and recent mosques have been inspired by this combination, the use of a reinforced concrete dome without cavity resonators could cause long reverberation times especially in low frequencies. The purpose of this study was to investigate this condition by studying Kocatepe Mosque. The acoustical characteristics of the mosque were analyzed by computer simulation. Objective room-acoustic indicators including reverberation time (RT), early decay time (EDT), clarity (C80), definition (D50), lateral fraction (LF), speech transmission index (STI) and strength (G) are presented. The results show that the acoustical quality of Kocatepe Mosque is not optimal when it is empty, and closest to optimal conditions when fully occupied. The new techniques to overcome excessive low frequency attenuation caused by huge concrete shells of today's mosques are discussed in conclusion. © 2008 University of Sydney. All rights reserved

Understanding the indoor soundscape in public transport spaces: A case study in Akköprü metro station, Ankara

Metro stations can be included in the indoor soundscape literature. This study examines the relationship between space recognition and soundmarks. Sound recordings were taken at various sites in and around a metro station and a listening test applied to investigate whether spaces could be recognized only by the sounds associated with them. For each sound recording, participants were asked to describe the recorded space from 17 adjective pairs and define the sound sources. The results are as follows: (1) only half of the participants were able to correctly determine the function of the spaces; (2) bird, wind, and water soundmarks were identified in the urban park near the metro station; pay gates and coin sounds were identified in the station entrance; and the metro train itself, as well as its brakes, doors, and announcement system, were identified on the underground platform; (3) for outdoor spaces, participants tended to choose adjectives such as pleasant, calming, or natural, while for indoor spaces they chose words such as unpleasant, stressing, and artificial; and (4) females on average are able to identify 30% more sounds correctly than males are, and younger age groups’ correct identification rate is greater than older groups’ by 10% on average. © The Author(s) 2017

A critical analysis of sunlight patches in patient rooms via simulation

Recent research on patient recovery has indicated significant improvement in the conditions of patients treated in sunny rooms compared to those treated in shaded rooms. In this study, the amount of sunlight received in patient rooms with different orientations and opening positions was observed. Desktop Radiance 1.02 software was used to simulate the conditions in a typical double patient room. The area and location of sunlight patches on room surfaces were considered as analog indicators for the investigation. Seven orientations and three positions of standard window openings were studied on an hourly basis in different combinations at solstices and equinoxes from sunrise to sunset. Data were statistically analyzed for advantageous combinations of orientation and opening positions. Results indicated that rooms with right- and left-shifted openings receive direct sunlight more than rooms with centered openings, and these have sunlight mostly on walls, while those with centered openings have it mostly on floors. The study revealed that opening positions rather than orientation is crucial to the design of patient rooms regarding the penetration of sunlight. Orientation is effective only when the room surfaces are studied individually. The study enabled sun patches to be visualized in relation to patient beds, which is a significant determinant that can affect the location of the bed, and so patient in the room. The paper concludes with four proposals of an informal choice from these combinations that both admits sunlight and protects the patient from glare and excessive heat gain. © 2008 University of Sydney. All rights reserved

The effects of achromatic and chromatic color schemes on participants' task performance in and appraisals of an office environment

This study explores the effects of chroma on participants' performance and environmental appraisal of an office. The research was conducted in a full-scale experimental room designed as a private office where achromatic and chromatic color schemes with coequal values were applied. Sixty participants were assigned tasks and given a questionnaire to appraise the spatial color schemes. The findings show that chroma significantly affects performance and space appraisal. In terms of accuracy and time spent performance scores measured significantly better in the room with the chromatic scheme than those in the room with the achromatic scheme. The office with the chromatic scheme was found to be more pleasant, attractive, satisfying and dynamic than the one with the achromatic scheme, whereas the achromatic scheme was thought to be more formal and harmonious. Categorization of pleasantness, harmony, dynamism and spaciousness by factor analysis also showed differences between the achromatic and chromatic schemes. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2012 Copyright © 2011 Wiley Periodicals, Inc