{"title":"Experimental Study on Sound Insulation of Ventilation Partitions","authors":"Liangfen Du, S. Lau, S. Lee","doi":"10.20900/joa20190005","DOIUrl":"https://doi.org/10.20900/joa20190005","url":null,"abstract":"Plenum windows that ensure noise reduction and natural ventilation at the same time have been studied by many researchers. Without sacrificing the window transparency and ventilation, limited acoustical treatments could be implemented in the cavity between two glass panes to enhance noise reduction performance of plenum windows, and accordingly the sound insulation performance by plenum windows hits a bottleneck. Ventilation partition with a similar configuration to plenum windows and consisting of two opaque partition panels with staggered openings is proposed. The paper experimentally studies the sound transmission loss of six ventilation partitions with different acoustical treatments. The measurement results show that their sound transmission class (STC) ratings can be up to 21 STC points higher than that without any acoustical treatment, and the sound transmission losses are even higher than that of a closed single-layered partition at middle and high frequencies with respect to specific designs. The STC of the six ventilation partitions with acoustical treatments investigated in the present study is between STC 22 and STC 32, more than 11 STC points higher than that without any treatment.","PeriodicalId":42518,"journal":{"name":"Romanian Journal of Acoustics and Vibration","volume":"78 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2019-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90311903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Acoustical Perceptions of Building Occupants on Indoor Environmental Quality in Naturally-Ventilated Building Façades","authors":"Jeehwan Lee","doi":"10.20900/joa20190004","DOIUrl":"https://doi.org/10.20900/joa20190004","url":null,"abstract":"Accelerated growth of urban population and motor vehicles has resulted in constant exposure to urban traffic noise that is one of the significant environmental stressors in urban environments. The aim of this research as a preliminary study is to evaluate acoustical perceptions of building occupants on their dwelling satisfaction with outdoor traffic noise through naturally-ventilated glazed building facades in the Seoul metropolitan area. This area has the highest population density among the largest countries of Organization for Economic Co-operation and Development (OECD). First, quantitative data of the A-weighted equivalent continuous sound levels (LAeq) at six sites in the Seoul metropolitan area were analyzed, showing that LAeq exceeded the thresholds of noise level standards, 65 dB(A) for day-time (06:00 AM to 10:00 PM) and 55 dB(A) for night-time (10:00 PM to 06:00 AM) respectively. Second, a questionnaire survey was conducted to find the environmental impacts of urban noise transmission on building occupants’ comfort and their ventilation behaviors. It showed that approximately 87% of building occupants \u0000(n = 92) used mechanical ventilation systems rather than window ventilation methods. Eighty-two percent of participants have experienced sick building syndrome (SBS)-related symptoms such as skin irritations or coughs. Thirty-three percent of the respondents were deterred from opening windows for natural ventilation due to outdoor traffic noise transmission, and 49% of respondents complained mostly of poor task productivity. The survey outcomes propose the importance of acoustically-treated ventilation openings in naturally-ventilated glazed building facades for building occupants’ indoor environmental quality in high-noise urban areas.","PeriodicalId":42518,"journal":{"name":"Romanian Journal of Acoustics and Vibration","volume":"35 1 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2019-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79901285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Sparse Time–Frequency Representation for the Transient Signal Based on Low-Rank and Sparse Decomposition","authors":"Liang Yu, Wei Dai, Shichun Huang, Weikang Jiang","doi":"10.20900/JOA20190003","DOIUrl":"https://doi.org/10.20900/JOA20190003","url":null,"abstract":"Rolling element bearings are important parts of rotating machinery, and they are also one of the most fault-prone parts in rotating machinery. Therefore, many new algorithms have been proposed to solve the vibration-based diagnosis problem of rolling bearings. The measured vibration signal is typically composed of a periodic transient signal severely contaminated by loud background noise when the faults occur. In this paper, a transient signal extraction algorithm is proposed which depends on spectrum matrix decomposition. The sparse time–frequency representation of the periodic transient signals is exploited, and, further, a low-rank and sparse model is established to extract transient signals from strong noise. First, the low-dimensional representation matrix of the measured signal is generated by the synchrosqueezing transform based on short-time Fourier transform. It is found that the low-rank of the transient signal will be approximately preserved in the transformed domain. Then, semi-soft go decomposition is used to decompose the spectrum matrix into a low-rank matrix and a sparse matrix. Finally, the transient signal can be recovered through the inverse transformation of the decomposed low-rank matrix. The proposed method is a data-driven approach, and it does not require prior training. The performance of the algorithm is investigated on both synthetic and real vibration signals, and the results demonstrate that the algorithm is effective and robust.","PeriodicalId":42518,"journal":{"name":"Romanian Journal of Acoustics and Vibration","volume":"49 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2019-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86724487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Virtual Special Issue: Natural Ventilation-Enabling Noise Reduction Facilities for Building Applications","authors":"S. Tang","doi":"10.20900/JOA20190002","DOIUrl":"https://doi.org/10.20900/JOA20190002","url":null,"abstract":"","PeriodicalId":42518,"journal":{"name":"Romanian Journal of Acoustics and Vibration","volume":"39 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78761233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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