Research On Methods For Estimating Reverberation Time In Structural Acoustics

As to different modern buildings, people need these various functional halls can provide good auditory effects, which mainly depends on the indoor acoustical parameter, including total sound level, uniformity of sound field, articulation and clarity, reverberation time(RT) etc., among which RT is an important parameter to describe room acoustical characteristics. During a century of development, RT has become an important and reliable criterion.The importance of RT not only exists in the objective evaluation for room sound quality, but also lies in the absorption measurement of sound-absorbing material. Moreover, RT has always been generally accepted as the fundamental, objective and well subjective feeling-related parameter. Thus, the research on RT lays the groundwork for the development of Engineering Acoustics.There are two methods now to measure RT. One of them is called Steady-state Noise Interrupting Method (SNIM) and the other is Impulse Integrated Method (ⅡM). The former method is widely-used because its operation is simple. It means that only by conducting ensemble mean on the sound level attenuation data, can we get the final sound level attenuation curve. The shortcomings, however, cannot be ignored, e.g., due to the decay curve would be easily affected by the random fluctuation from outsides. Repeated measurements would be carried out to ensure an accurate result. In comparison, using ⅡM can enable a smooth curve by only one-time measurement, and the result of RT is more accurate.In this paper, firstly, based on EASE software, an acoustical solid model for normal laboratory and academic lecture hall is made according to the plans, elevations and decorate material. Through defining the material on the wall, the simulated RT can be obtained. A testing measurement is then performed to collect signal in different sound-source positions and microphone positions. During the whole process, the sound attenuation curve of unsteady-state noise and the impulse signal excitation are both collected. After that, the actual testing RT can be obtained by the programming of algorithm based on NI LabVIEW software, during which the sliding window-truncation algorithm is proposed to evaluate RT. At last, make comparison to different sound source with the simulated RT, and a more accurate method is obtained, which provides a reference to the practical problems.