Absolutely Not! I recently read a quip from a man on a public speaking social media website who is working with a voice coach. He said that "her normal talking voice in a one on one situation is massively different to her 'performance' speaking voice."
When I coach my clients, I explain that their real voice is one powered by means of the chest cavity and has more depth and resonance than their habitual voice; however, I do not tell them that it is a 'performance' voice to be used only on stage. Whether I am teaching, talking to my family, giving a presentation, or being interviewed for radio or TV, I sound the same.
Performance is a very loose term and can certainly refer to the delivery of a speech or presentation; however, it is not common to hear. After listening to the dynamic delivery of a message, we would rather say how good the presentation or the presenter and not how good the performance. On the other hand, we would most certainly would use the word performance when discussing a play, a concert, or some other type of stage production. Further still, that word can be used when describing how well a car operates on the road or how efficiently a worker does his/her job.
Public speaking is the art of oral communication with an audience. The preposition of note in this definition is the word with. It does not say at, to, or for an audience and is one of the major differences between performing and speaking. If we look at the possibilities of the use of the term 'performing' in the sense of music, acting, or even a sporting event, with an audience is not part of the definition. Most certainly, it is for or to an audience, but not with them.
In acting, for example, you take on the 'voice' of another character. That is the performance. In public speaking, however, those who are most successful, like Zig Ziglar, Jack Canfield, or Brian Tracy, sound the same whether they are talking with you on stage or off. Good radio and television broadcasters sound the same whether they are in front of a microphone or off the air.
Do not believe that you should have a different voice when addressing an audience. Whether you speaking to 5 people or 500 or whether you are standing around the water cooler at work, only one voice is necessary. If you want to be a dynamic speaker, stop performing and start communicating with your audience in one voice.