If you are performing an experiment (delivering a speech) and need to know a critical outcome along the way (audience reaction/awareness) you have to measure it (video or audio record your speech) to see the results.
Just as a scientist would do in his/her lab, you must do in your lab, and, in this case, your lab is your speaking environment, your lab is your speech delivery, or maybe your lab is the experimental process you follow so you will know where you are along the way in your speech and where you need to add, delete, or change (adjust your speech volume or intonation) to get to the desired results you want (audience reaction, understanding, or Call to Action).
If things don’t work the first time, go back and review the audio/video recording and see where you can tune your message by making it shorter or more succinct and to the point, by observing body movements or vocal inflections, and by critiquing your overall message segueway(s) paying close attention to your ‘transitional’ words from point to point.
Today, data storage is cheap. Make the investment in a good recording device of some sort and start recording your speaking experiments so you can measure your speaking success along the way!