A PROPOSAL ON THE ACOUSTIC CHARACTERISTIC INDICES OF SOUND REINFORCING SYSTEM IN THE HALL

In this article,a proposal is made on the acoustic characteristic indices,such as maximum pinknoise sound pressure lcvel,frequency transmission characteristics,sound transmission gain,non-uniformity of sound field and distortion,and so on.They are based upon some measurements togetherwith the evaluation of using effect,and the operational performance of the electroacoustic facilitieswhich are available in China.Some experimental results and levels that have been achieved abroadare also taken into consideration.For the time being,the different levels of the acoustic characteristicindex being used are preferable for the speech or performance sound reinforcing System.     

内墙的隔声改善量

内墙的隔声改善量ΔR是受内、外墙间空腔和内墙的传声损失、以及墙间基础的传递损失所决定.从厚的外墙到比它薄的内墙传声中,不仅是降低了固体声速度级的绝对值,且内墙上的速度级分布,也在一定程度上反映出外墙上的速度级分布.因此,测量内、外墙上速度(或加速度)级差,可得到ΔR的近似值. 分离的双层墙,在最低简正频率以下,相当于质量阻抗时,内墙的ΔR-f曲线才以40dB/decade递增.实用的大面积内墙,其简正频率很快达到足够的密度,其弯曲波阻抗与频率无关,ΔR-f曲线以20dB/decade而递增. 墙间空腔填吸声材料或墙内加阻尼材料都可提高隔声量.双层墙共用基础或分离基础但无隔振器,则内墙的ΔR分别不大于9或18dB.要使内墙有较高的ΔR,应选用适当f_0的隔振器.压缩量随时间而变的隔振材料不宜用做为隔振器.     

厅堂扩声系统声学特性指标的建议

本文对厅堂扩声系统的最大粉红噪声声压级、传输频率特性、传声增益、声场不均匀度、失真等声学特性指标提出建议。它是以一些测量和使用效果的评价以及我国电声设备达到的使用特性为基础,还考虑了某些实验结果和国外达到的水平。当前对语言或演出用的扩声系统采用不同等级的声学特性指标是可取的。     

扩声系统的传声增益

本文给出传声增益的计算方法,并用声反馈系数的测量来决定传输响应中最大峯级和平均级之间的差值.它可简化测量技术,并能用于扩声系统的声学设计.