The present paper is aimed to study the effect of Gaussian laser light on first and second sound waves in superfluid helium theoretically using optoacoustic method. The mechanism applied in this study is electrostrict...The present paper is aimed to study the effect of Gaussian laser light on first and second sound waves in superfluid helium theoretically using optoacoustic method. The mechanism applied in this study is electrostriction mechanism. This study considers crystal parts of superfluid helium with a zero absorption coefficient applying electrostriction mechanism. Affecting Gaussian laser light on these crystal parts, a spectrum of cylindrical first and second sound waves and cylindrical slow and rapid waves is obtained. Meanwhile, frequency of waves amplitudes proportionate to time period of laser light is calculated.展开更多
Light travels at a speed which is about a million times faster than the speed of sound. In one second, light travels about 300,000 km, but sound travels only 314m, you can get some idea of this difference(区别) by wat...Light travels at a speed which is about a million times faster than the speed of sound. In one second, light travels about 300,000 km, but sound travels only 314m, you can get some idea of this difference(区别) by watching the start of a race.展开更多
Light frame walls(LFWs) serve as common partition walls in prefabricated buildings due to their lightweight nature, costeffectiveness, energy efficiency, and adaptability for rapid on-site assembly. However, their aco...Light frame walls(LFWs) serve as common partition walls in prefabricated buildings due to their lightweight nature, costeffectiveness, energy efficiency, and adaptability for rapid on-site assembly. However, their acoustic insulation capability is hindered by issues such as sound bridges, resonance, and coincidence dips, resulting in inadequate sound insulation. This study aims to propose LFW designs with superior acoustic insulation suitable for practical engineering while meeting prevailing national standards. Nine full-scale LFW configurations were subjected to laboratory testing to evaluate the impact of staggered stud arrangements, stud types, and incorporation of compounded materials. The tests were performed between 100 and 5000 Hz,and the sound pressure level and reverberation time at 1/3 octave band were measured and used to calculate the weighted sound insulation index(Rw). Results demonstrated that the outlined design modifications significantly enhanced the sound insulation of the LFW. These modifications effectively mitigate the influence of sound bridges while addressing resonance and coincidence dips inherent in the wall system. Particularly noteworthy was the superior sound insulation achieved by staggered-stud LFWs with compounded materials, surpassing that of autoclaved lightweight concrete walls commonly used in prefabricated constructions despite having lesser thickness and surface density. Rwvalues increased from 43 to 54 dB compared to conventional LFWs, translating to a notable elevation in airborne sound insulation level from 4 to 7 as an internal separation component,meeting the requisite standards for most applications.展开更多
文摘The present paper is aimed to study the effect of Gaussian laser light on first and second sound waves in superfluid helium theoretically using optoacoustic method. The mechanism applied in this study is electrostriction mechanism. This study considers crystal parts of superfluid helium with a zero absorption coefficient applying electrostriction mechanism. Affecting Gaussian laser light on these crystal parts, a spectrum of cylindrical first and second sound waves and cylindrical slow and rapid waves is obtained. Meanwhile, frequency of waves amplitudes proportionate to time period of laser light is calculated.
文摘Light travels at a speed which is about a million times faster than the speed of sound. In one second, light travels about 300,000 km, but sound travels only 314m, you can get some idea of this difference(区别) by watching the start of a race.
基金supported by Jiangsu Science and Technology Project (Grant No. BE2022790)the Special Fund for Green Building Development in Jiangsu Province (Grant No. (2021) 62-42)the Open Research Fund of Key Laboratory of Architectural Acoustic Environment of Anhui Higher Education Institutes (Grant No. AAE2021YB02)。
文摘Light frame walls(LFWs) serve as common partition walls in prefabricated buildings due to their lightweight nature, costeffectiveness, energy efficiency, and adaptability for rapid on-site assembly. However, their acoustic insulation capability is hindered by issues such as sound bridges, resonance, and coincidence dips, resulting in inadequate sound insulation. This study aims to propose LFW designs with superior acoustic insulation suitable for practical engineering while meeting prevailing national standards. Nine full-scale LFW configurations were subjected to laboratory testing to evaluate the impact of staggered stud arrangements, stud types, and incorporation of compounded materials. The tests were performed between 100 and 5000 Hz,and the sound pressure level and reverberation time at 1/3 octave band were measured and used to calculate the weighted sound insulation index(Rw). Results demonstrated that the outlined design modifications significantly enhanced the sound insulation of the LFW. These modifications effectively mitigate the influence of sound bridges while addressing resonance and coincidence dips inherent in the wall system. Particularly noteworthy was the superior sound insulation achieved by staggered-stud LFWs with compounded materials, surpassing that of autoclaved lightweight concrete walls commonly used in prefabricated constructions despite having lesser thickness and surface density. Rwvalues increased from 43 to 54 dB compared to conventional LFWs, translating to a notable elevation in airborne sound insulation level from 4 to 7 as an internal separation component,meeting the requisite standards for most applications.
