There may be two situations where you will be speaking through an interpreter. The most obvious is when you are speaking a foreign language. There is another kind of English that most are not aware of. It is called ASL or American Sign Language. It is used by the deaf.
There are some preparations in common and some differences in speaking through an interpreter in these two situations. It should also be noted that the deaf do not view themselves as handicapped. There are some cultural differences you will benefit from being aware of when speaking to other languages as well as ASL.
If you are not already speaking in short sentences, it will be good to start. Unless there is technical details that can be read in the language of the native speakers, the speaking time will have to be cut in half for a language foreign to you. This is all part of the preparation.
Speaking to the deaf will be the same time or slightly shorter depending on the skill of the person signing. Signing happens almost simultaneously with the words you speak. Pausing will help make the job easier.
Your preparation for delivering your public speech includes helping the interpreter to be prepared. Regardless of the experience level of the interpreter, this is an essential process. Initially it would be good if the entire speech was reviewed.
Avoid idioms. If you should use them, make sure the interpreter understands and can properly convey the thoughts you want to the language group your speaking to.
When speaking of medical or technical terms, it will be good if the interpreter is able to understand what you are talking about.
Prior to delivering...
Review your objectives.
Review any illustrations you will be using in your speech.
Review illustrations to explain difficult to understand terms.
Review your introduction and conclusion and any important parts that are essential key points for your objectives.
Speak in complete sentences and complete thoughts.
Allow the interpreter to finish before you start your next thought.
When Speaking to the Deaf:
Some may have some degree of hearing. Many can also read lips. Make sure to enunciate words and speak clearly. As stated above, speak in sort complete sentences.
Make sure to use pauses effectively.
The signer will be very demonstrative in both face and body movement. Do not let that distract you from your delivery.
Public speaking through an interpreter is only one more way to attain mastery of the public speaking business. Preparation is key to your success.
Whether signing to the deaf or speaking to another language, you can be successful if you prepare.