Once actors have been chosen and rehearsals begin, it's time for intense study of the script and any professional actor will undertake background research to get a good grasp of the role. Throughout rehearsals, actors memorise lines, rehearse movements, mannerisms, and interactions with other characters. Actors use different methods to immerse themselves in a character. Characterisation is developed with either an externalised approach or a personalised approach. Externalising means, for example, adopting a character's distinctive walk and developing the character from that point. Personalisation is the technique where actors identify with a character from their own life experience to make a character more whole, more believable. Such methods may come naturally to some actors, but these skills are also developed during their training. Another essential quality, which may come naturally but is generally developed through training, is a clear, strong voice that can be altered to suit different characters. Voice projection is not just about having a loud voice. It is equally the ability to whisper on stage and still be heard in the back row of a theatre.