Nonlinear filtering of impulse response obtained by M-sequence correlation method under strong background noise is presented. The research shows that the new method works very efficiently without the need ...Nonlinear filtering of impulse response obtained by M-sequence correlation method under strong background noise is presented. The research shows that the new method works very efficiently without the need to cut off impulse response data. Even if the ratio of signal to noise is below -15 dB, the same decay curve ranges can still be obtained as when S/N > 40 dB展开更多
China’s coastal waters are turbid and the properties of the seabed are complex. This negatively impacts the performance of underwater detection equipment. The properties of sound absorption in turbid water are not we...China’s coastal waters are turbid and the properties of the seabed are complex. This negatively impacts the performance of underwater detection equipment. The properties of sound absorption in turbid water are not well understood. In this paper, the coefficient of sound absorption in turbid water was measured by the reverberation technique. All work was done in a reverberation barrel made of seamless aluminum. First, pure water was poured into the reverberation barrel and its reverberation time measured. Next, various concentrations of turbid water were poured into the barrel and their reverberation time measured. After all data had been gathered, the coefficient of sound absorption in turbid water of different concentrations was calculated. From this we determined a law of sound absorption in turbid water as summarized in the paper.展开更多
Here we report first ever study on acoustical evaluation of Kanheri Caves located in Sanjay Gandhi National Park,Mumbai(Maharashtra,India).These caves are dated to a period between 2nd century BCE to 7th century CE.In...Here we report first ever study on acoustical evaluation of Kanheri Caves located in Sanjay Gandhi National Park,Mumbai(Maharashtra,India).These caves are dated to a period between 2nd century BCE to 7th century CE.In this study we used an ambisonic recorder to capture Impulse Response,which carries acoustic signature of the place.Out of total 109 caves 41 were surveyed in available time.Out of those reverberant environment was noted in 12 caves.Measurements were made only in 3 caves(Cave Nos.1,3,11)which are important.In the beginning we carried out an FFT analysis.We then studied room acoustic parameters like Reverberation Time,Early Decay Time,Clarity,Definition,etc.,based on the measurement of Impulse response.Cave No.3 have high value of reverberation time,compared to other.Therefore it also have lower clarity compared to others.It is properties needs to be compared with similar structures(chaityas)in Maharashtra(at Ajanta,Ellora,Nashik,Junnar,etc.)and elsewhere in India.It is worthwhile to carry out further research in Cave No.3 with more sophisticated instruments as well as 3D modeling.Since the experiment was performed with receiver at only one position,we also suggest to carry out experiment with receiver at multiple positions and then comparing them.展开更多
The new guidelines of the Catholic Church are in line with the guidelines adopted by Protestant churches since the Reformation, unifying appreciation for the liturgical practices of preaching and congregational singin...The new guidelines of the Catholic Church are in line with the guidelines adopted by Protestant churches since the Reformation, unifying appreciation for the liturgical practices of preaching and congregational singing. These guidelines require that the room, in this case the church, provides appropriate acoustic characteristics, which can be characterized by acoustic descriptors such as Reverberation Time (RT), Clarity (C80) and Definition (D50). In this article, we analyzed the acoustic quality of a protestant church whose design tried to follow these guidelines. Our findings revealed the poor quality of the acoustic environment in terms of both speech intelligibility and music. These findings emphasized the need to adopt not only Reverberation Time but also other acoustic descriptors such as Clarity and Definition in church design.展开更多
Based on the commonly used indicators for speech intelligibility, this work acoustically evaluates the two largest auditoria in the Faculty of Engineering, Helwan University, Cairo, Egypt, using experimental and digit...Based on the commonly used indicators for speech intelligibility, this work acoustically evaluates the two largest auditoria in the Faculty of Engineering, Helwan University, Cairo, Egypt, using experimental and digital simulation techniques. Design treatments were also suggested to improve the acoustic performance of the auditoria, where the impact of these treatments was checked using the simutation as well. The models that were analysed using the CATT-software were first validated utilizing the results of the fietd work in the unoccupied rooms. The results showed that the acoustic quality of the two auditoria are far from the optimal conditions due to their improper acoustic characteristics and the high noise revers as weft. The results of improvement proposals showed that altering the ceiling shape and adding efficient absorptive materials to the rear surfaces successfully reduced the excessive reverberation time to the optimal values, increased the earty reflections and eliminated the shadow zones. In addition, decreasing the noise Levels by 20 dB due to improving the window insulation noticeably improved the speech intelligibitity at all receivers.展开更多
Cork is a sustainable material and at the end of its useful life it can be disposed of into the environment without causing damage.This paper analyzes an acoustic correction system made of cork sheets mounted at an op...Cork is a sustainable material and at the end of its useful life it can be disposed of into the environment without causing damage.This paper analyzes an acoustic correction system made of cork sheets mounted at an opportune distance from the walls inside a room.The cork sheets have a thickness equal to 1.5 mm.The sound absorption coefficients of the cork sheets were initially evaluated by mounting samples inside an impedance tube,then creating a back cavity at a suitable distance from a rigid wall.The distances considered were:3,5,10 and 15 cm.A room used as an office with a volume of about 90 m^(3)and plastered walls was considered as a case-study.In this type of environment,suitable acoustic comfort conditions are required.The acoustic characteristics were analyzed through a virtual model with an architectural acoustics software in an empty room and then with the introduction of sound-absorbing cork sheets.Measurements of the acoustic characteristics of the empty room were taken and subsequently with the walls lined with cork panels mounted at a distance of 3.0 cm from the rigid rear wall.A configuration was analyzed,in line with what was carried out in the numerical model,covering a surface of 5m^(2)of the room.The results of the numerical simulations as well as the experimental measurements are discussed.展开更多
文摘Nonlinear filtering of impulse response obtained by M-sequence correlation method under strong background noise is presented. The research shows that the new method works very efficiently without the need to cut off impulse response data. Even if the ratio of signal to noise is below -15 dB, the same decay curve ranges can still be obtained as when S/N > 40 dB
文摘China’s coastal waters are turbid and the properties of the seabed are complex. This negatively impacts the performance of underwater detection equipment. The properties of sound absorption in turbid water are not well understood. In this paper, the coefficient of sound absorption in turbid water was measured by the reverberation technique. All work was done in a reverberation barrel made of seamless aluminum. First, pure water was poured into the reverberation barrel and its reverberation time measured. Next, various concentrations of turbid water were poured into the barrel and their reverberation time measured. After all data had been gathered, the coefficient of sound absorption in turbid water of different concentrations was calculated. From this we determined a law of sound absorption in turbid water as summarized in the paper.
文摘Here we report first ever study on acoustical evaluation of Kanheri Caves located in Sanjay Gandhi National Park,Mumbai(Maharashtra,India).These caves are dated to a period between 2nd century BCE to 7th century CE.In this study we used an ambisonic recorder to capture Impulse Response,which carries acoustic signature of the place.Out of total 109 caves 41 were surveyed in available time.Out of those reverberant environment was noted in 12 caves.Measurements were made only in 3 caves(Cave Nos.1,3,11)which are important.In the beginning we carried out an FFT analysis.We then studied room acoustic parameters like Reverberation Time,Early Decay Time,Clarity,Definition,etc.,based on the measurement of Impulse response.Cave No.3 have high value of reverberation time,compared to other.Therefore it also have lower clarity compared to others.It is properties needs to be compared with similar structures(chaityas)in Maharashtra(at Ajanta,Ellora,Nashik,Junnar,etc.)and elsewhere in India.It is worthwhile to carry out further research in Cave No.3 with more sophisticated instruments as well as 3D modeling.Since the experiment was performed with receiver at only one position,we also suggest to carry out experiment with receiver at multiple positions and then comparing them.
文摘The new guidelines of the Catholic Church are in line with the guidelines adopted by Protestant churches since the Reformation, unifying appreciation for the liturgical practices of preaching and congregational singing. These guidelines require that the room, in this case the church, provides appropriate acoustic characteristics, which can be characterized by acoustic descriptors such as Reverberation Time (RT), Clarity (C80) and Definition (D50). In this article, we analyzed the acoustic quality of a protestant church whose design tried to follow these guidelines. Our findings revealed the poor quality of the acoustic environment in terms of both speech intelligibility and music. These findings emphasized the need to adopt not only Reverberation Time but also other acoustic descriptors such as Clarity and Definition in church design.
文摘Based on the commonly used indicators for speech intelligibility, this work acoustically evaluates the two largest auditoria in the Faculty of Engineering, Helwan University, Cairo, Egypt, using experimental and digital simulation techniques. Design treatments were also suggested to improve the acoustic performance of the auditoria, where the impact of these treatments was checked using the simutation as well. The models that were analysed using the CATT-software were first validated utilizing the results of the fietd work in the unoccupied rooms. The results showed that the acoustic quality of the two auditoria are far from the optimal conditions due to their improper acoustic characteristics and the high noise revers as weft. The results of improvement proposals showed that altering the ceiling shape and adding efficient absorptive materials to the rear surfaces successfully reduced the excessive reverberation time to the optimal values, increased the earty reflections and eliminated the shadow zones. In addition, decreasing the noise Levels by 20 dB due to improving the window insulation noticeably improved the speech intelligibitity at all receivers.
文摘Cork is a sustainable material and at the end of its useful life it can be disposed of into the environment without causing damage.This paper analyzes an acoustic correction system made of cork sheets mounted at an opportune distance from the walls inside a room.The cork sheets have a thickness equal to 1.5 mm.The sound absorption coefficients of the cork sheets were initially evaluated by mounting samples inside an impedance tube,then creating a back cavity at a suitable distance from a rigid wall.The distances considered were:3,5,10 and 15 cm.A room used as an office with a volume of about 90 m^(3)and plastered walls was considered as a case-study.In this type of environment,suitable acoustic comfort conditions are required.The acoustic characteristics were analyzed through a virtual model with an architectural acoustics software in an empty room and then with the introduction of sound-absorbing cork sheets.Measurements of the acoustic characteristics of the empty room were taken and subsequently with the walls lined with cork panels mounted at a distance of 3.0 cm from the rigid rear wall.A configuration was analyzed,in line with what was carried out in the numerical model,covering a surface of 5m^(2)of the room.The results of the numerical simulations as well as the experimental measurements are discussed.
