Glass and Singer(1972)showed that situations in which there is intense noise have less effect on performance than circumstances in which unexpected noise occurs.

have 为宾语从句谓语，主语为：situations， having为非谓语动词，所以不能把谓语动词have改为非谓语动词having。

主句语法结构分析如下

主语：Glass and Singer(1972)

谓语：showed

宾语从句:that situations in which there is intense noise have less effect on performance than circumstances in which unexpected noise occurs.

宾语从句语法结构分析如下

引导宾语从句连词：that

主语：situations

修饰主语后置定语从句：in which there is intense noise

谓语:have

宾语:less effect

状语:performance than circumstances in which unexpected noise occurs.