Theatre productions require careful sound design and mixing to ensure the actors voices are heard clearly over the orchestra. Wireless microphones are often used, with 41 microphones for one show, attached discreetly using medical tape. The sound designer determines optimal speaker placement to reach the audience. During a performance, the sound mixer controls volume levels, balances different audio sources, and turns channels on and off precisely according to the script. They must have an expert knowledge of the show. Assistant sound engineers prepare microphones and address any technical issues.