The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field...The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field is developed. First, the conventional method for gas pulsation measurement and prediction, which separates the incident and reflected wave of acoustic waves traveling in the frequency domain, is discussed. Then, regression based on our proposed simple model, which is able to predict gas pulsation compared to the conventional method, is introduced for the analysis of a reciprocating compressor(The conventional method requires the value of sound speed in the piping line for the reciprocating compressor). A numerical prediction is made for the regression method. Three power spectrum values along the discharge pipeline are used for analysis, and two values are used for verification. Our results are in a good agreement with the conventional method.展开更多
Detection and localization of acoustic events in an environment are important to protect the military and civilian installations. While there are finite paths of wave propagation in simple or low reverberant environme...Detection and localization of acoustic events in an environment are important to protect the military and civilian installations. While there are finite paths of wave propagation in simple or low reverberant environments, in complex environments (e.g. a complex urban environment) obstacles such as terrain or buildings introduce multipath propagations, reflections and diffractions which make source localization challenging. Therefore, numeric results of simulated models (simplified and Fort Benning urban models) of 3D complex environments can highly help in real applications. Some of the conventional beamformer algorithms have been used in order to localize point sound source. Analyzing results shows that MRCB beamformer has better performance than others in this issue and its accuracy superiority is more than 3 m in simplified urban model and 5 m in Fort Benning urban model with respect to the SOC. Moreover, due to possible uncertainties between the numerical model and the actual environment such as squall effect, temperature gradient etc., sensitivity of the beamformers to temperature gradient is investigated which shows higher robustness of SOC beamformer than the MRCB beamformer. According to the results, due to gradient temperature uncertainty the accuracy degradation of the SOC is about 1m while in MRCB it alters from 0.5 m to 20 m approximately at all SNRs. COMSOL Multiphysics has been used to numerically simulate the environment of wave propagation.展开更多
Reverberation time within studio’s decor is changed because of addition of its surface to the overall surfaces of the studio and also the additional absorption of its materials. It seems reverberation time changes du...Reverberation time within studio’s decor is changed because of addition of its surface to the overall surfaces of the studio and also the additional absorption of its materials. It seems reverberation time changes due to studio’s decor is little because surface of the decor is small in comparison with the overall surfaces of the studio and surface has an important role in room constant and therefore in reverberation time. But these changes do not only depend on added surfaces and their absorption. Reverberation time is also dependent on shape of the decor and sometimes. It can decrease the effects of added surfaces which are used to increase the reverberation time. In this paper, a standard television studio is designed and implemented by using ODEON and 12 different decor which their dimensions and materials are similar to the actual ones, are applied inside the studio. Then studio’s decor effects on reverberation time of the studio are computed, compared and analyzed.展开更多
基金Project supported by the 2010 Yeungnam University Research Grant,Korea
文摘The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field is developed. First, the conventional method for gas pulsation measurement and prediction, which separates the incident and reflected wave of acoustic waves traveling in the frequency domain, is discussed. Then, regression based on our proposed simple model, which is able to predict gas pulsation compared to the conventional method, is introduced for the analysis of a reciprocating compressor(The conventional method requires the value of sound speed in the piping line for the reciprocating compressor). A numerical prediction is made for the regression method. Three power spectrum values along the discharge pipeline are used for analysis, and two values are used for verification. Our results are in a good agreement with the conventional method.
文摘Detection and localization of acoustic events in an environment are important to protect the military and civilian installations. While there are finite paths of wave propagation in simple or low reverberant environments, in complex environments (e.g. a complex urban environment) obstacles such as terrain or buildings introduce multipath propagations, reflections and diffractions which make source localization challenging. Therefore, numeric results of simulated models (simplified and Fort Benning urban models) of 3D complex environments can highly help in real applications. Some of the conventional beamformer algorithms have been used in order to localize point sound source. Analyzing results shows that MRCB beamformer has better performance than others in this issue and its accuracy superiority is more than 3 m in simplified urban model and 5 m in Fort Benning urban model with respect to the SOC. Moreover, due to possible uncertainties between the numerical model and the actual environment such as squall effect, temperature gradient etc., sensitivity of the beamformers to temperature gradient is investigated which shows higher robustness of SOC beamformer than the MRCB beamformer. According to the results, due to gradient temperature uncertainty the accuracy degradation of the SOC is about 1m while in MRCB it alters from 0.5 m to 20 m approximately at all SNRs. COMSOL Multiphysics has been used to numerically simulate the environment of wave propagation.
文摘Reverberation time within studio’s decor is changed because of addition of its surface to the overall surfaces of the studio and also the additional absorption of its materials. It seems reverberation time changes due to studio’s decor is little because surface of the decor is small in comparison with the overall surfaces of the studio and surface has an important role in room constant and therefore in reverberation time. But these changes do not only depend on added surfaces and their absorption. Reverberation time is also dependent on shape of the decor and sometimes. It can decrease the effects of added surfaces which are used to increase the reverberation time. In this paper, a standard television studio is designed and implemented by using ODEON and 12 different decor which their dimensions and materials are similar to the actual ones, are applied inside the studio. Then studio’s decor effects on reverberation time of the studio are computed, compared and analyzed.
