Research On The Relationship Between STI And Lateral Energy Fraction Based On Simulation

This paper studies the relationship between the speech transmission index and the lateral energy fraction based on simulation.The speech transmission index STI is an objective evaluation of speech intelligibility,which can take into account the effects of reverberation time and signal-to-noise ratio at the same time.And the STI direct method can resist some distortion,so it is adopted by the IEC standard and have become an important indicator of sound comfort.The lateral energy fraction LF is a parameter that evaluates the proportion of early lateral reflection sound energy in the total sound energy.Early reflection sound also plays a very important role in halls,but LF gets less attention than other parameters.These two parameters are generally designed and controlled in the language and music halls,but it is still unclear how the relationship between the two parameters is.In the actual measurement,there are always large errors due to LF's measurement method,and it is difficult to obtain a wide range of acoustic conditions in the real environment.Therefore,acoustic simulation was used to study the relationship.Language halls such as ladder classrooms have a larger area and volume.They can hold a larger number of students.Music halls such as concert halls pay more attention to the uniformity and fullness of the sound.Although the emphasis of the two types of halls' acoustic evaluation is slightly different,the relationship between the energy distribution in the sound field and the influence of the transmission is all the same.In order to make the research more comprehensive,this article took 7 ladder classrooms in Dalian University of Technology and Goteborg Koncerthus Concert Hall in ODEON as research objects.After the actual acoustic measurement of the ladder classrooms,ODEON software was used to simulate them.The Genetic Material Optimizer in ODEON was used to match the acoustic materials.Also,rooms were carefully matched and optimized to get the most realistic simulated sound field.After obtaining the acoustic parameters under different acoustic conditions in 7 classrooms and concert halls,the correlation analysis of various factors related to LF and STI was carried out.Linear regression was used to analyze the relationship between LFs,T30,SNR,location of measuring point,classroom type and STI.The relationship between STI and sound energy value is analyzed to verify and explain the negative correlation between STI and LF.LF measures the ratio of early lateral sound to the total sound energy.It can't fully reflect the number of sound energy levels.However,direct sound is significantly positively correlated with STI;but negative correlation correlated with LF.Therefore,LF and STI are weakly negatively correlated.When STI is the dependent variable,the linear regression normalization coefficient Beta values of LF50,LFC50,LF80,and LFC80 are-0.190,-0.216,-0.186,and-0.212,and the significance is 0.000.Afterwards,the classroom was simulated to verify the establishment of this relationship.In order to further verify the relationship between LF and STI,the Aurulisation module of ODEON software was used for subjective listening experiments.The simulated listening signals of different classrooms and points were mixed with the three kinds of background noise to obtain the final listening signal.After taking into account the fatigue,familiarity,signal penetration,etc.of the test subject,the subjective listening experiment score was obtained.After linear regression on the subjective scores,the conclusion that the LF and the subjective listening test scores are negatively correlated is obtained.Also,the relationship between LF and STI is verified.And through the comparison between the LF values,the LF80 parameter is still recommended.This paper studies the relationship between the speech transmission index and the lateral energy fraction,which provides a reference for the role of the two in the acoustic design of different halls.