The audience receives an uninterrupted translation of the speaker’s words as they are spoken. This usually requires two interpreters plus the basic hardware: a booth with reception and transmission equipment, and headphones for those listening.

Simultaneous interpretation is a complex cognition and processing activity comprising a series of interdependent events. The interpreters receive and listen to part of a sentence in the original language (a "translation byte", i.e. a unit of meaning) and immediately begin to interpret it to render it in the listeners’ language. Whilst still vocalising the "byte" already translated, we hear the next one in the original language and begin to repeat the same process with it. Interpreters are skilled at retaining the second "byte" in our short-term memory, where it queues to be said in the target language, and at the same time checking that the grammar and vocabulary we are using for the previous "byte" is correct. As you can imagine, to get this flowing smoothly requires intelligent understanding, effort and training, but the people listening in the audience are only aware that they are receiving the original speech in real time and in a language they understand. (We like to compare it to a ballet, where the best dancers are the ones that allow you to forget about the technique and concentrate on the ballet itself.)

What makes consecutive interpreting consecutive is that the interpreter only renders the speech in the target language once the speaker has ceased speaking instead of interpreting "over" what is being said. The technique can vary according to the interpreter’s own preference and the nature of the conference. With proper training, it is sometimes possible to reproduce an entire speech from memory, but usually interpreters take notes which we can then read back. A professional interpreter can translate everything that has been said without time limits. (There is no need to stop every two or three words!) We are also trained to pick up on and translate non-verbal messages, such as visual contact with the audience, smiles, frowns, persuasive or emphatic gestures, etc.

This is the least common type of simultaneous interpretation. It can only be used when there are a limited number of people who do not understand the original language. It is usually employed alongside consecutive interpretation, so that the person or people listening to the "chuchotage" can express themselves to speakers of the majority language. It is especially useful in small meetings or negotiations, where it is important for the people involved to react in real time.

In some cases, another variant can be used, "chuchotage with earphones". The interpreter brings a small suitcase with a microphone/transmitter and earphones, in order for our whispering to be heard by a slightly larger group of listeners.