Is my joke about my first talk at Nankai correct, understandable, and funny? I'm practicing my upcoming talk in Chinese, and I like to start talks with a light joke to appear friendly.  So I came up with this:

我第一次在南开学校作演讲，我用汉语讲第一句话，听众大声鼓掌以示回应。然后我说英语，但是听众听不懂，所以我讲完了时候，鼓掌比较小声。只是第一句话他们能听懂。希望我现在说的比较清楚。
The first time I gave a talk on the Nankai campus, I used Chinese for the first sentence, and the audience applauded loudly. Afterwards, I spoke English, but the audience didn't understand, so when I finished my talk, the applause was comparatively quiet.  They only understood the first sentence.  I hope my speaking now is clearer.

After this, I plan to go into the content of the talk.
Question: Is my joke about my first talk at Nankai correct, understandable, and funny?
Basically, I'm after some constructive criticism on this.  I'm not hugely fussed about it being the most optimal way to say this, but as long as it's not a semantic nor grammar disaster.  (There'll surely be plenty of other grammar mishaps when I get off-script.)
One thing I'm concerned about is if it's clear that the audience applauded directly after the first sentence (which I said in Chinese) before the remainder of the talk, which is an essential part of the joke.
I'm also not sure about 鼓掌比较小声 vs. 鼓掌声比较小.
I can see what you are trying to joke about. 

我第一次在南开学校作演讲 is a bit ambiguous. Some might take this is your first time to deliver a speech. So, out of that confusion, you can say ahead like: 这是我第二次在南开大学做演讲。 记得我第一次在这里演讲时，... 

So, here is a version I make for your reference:


  这是我第二次在南开大学做演讲。记得我第一次在这里演讲时，我用汉语讲第一句话来和大家打招呼，大家热烈鼓掌以示回应。接下来的演讲我一直用的是英语。可能是大家没怎么听懂，所以我讲完后，大家都没反应，似乎好像都不知道我已经讲完了！所以， 这一次我准备全程用中文来讲。 希望大家都可以听得明白。