Call a local theater company to see what upcoming shows they have planned. Ask them if they host field trips, and explain that you are exploring light and sound with your students. Community theaters are a great starting place, because they have strong ties to the community, but even commercial theaters foster relations with the community by inviting students to visit them.
Depending on your students' ages, you can discuss fear of the dark, the effect of bright lights, and other light and sound experiences they have. Invite them to close their eyes and pay attention to every sound in the room. Ask them to open their eyes and name something they see that they have never noticed before. Tell them you want to take them to the theater to see how light and sound enhance a play.
Most theaters have a technical rehearsal before opening night. They usually conduct this rehearsal during the day, during school hours. Ask if you can bring your students to the technical rehearsal to observe how the light and sound technicians go over their cues and practice their special effects.
Back in the classroom, read the text of the show that is being produced at your local theater. Ask the students to describe any sights or sounds they imagine as you read the play. Divide them into lighting directors and sound directors, and let them do group work where they imagine special effects that would enhance the story.
Take the students to see the professional production of the play. Many theater groups will host a free matinee for school groups. Others charge a fee, but you can often get funding through online grant companies like Donors Choose (donorschoose.org). Don't teach during the performance, just allow the children to enjoy it.
Back in the classroom, ask students to describe any light effects of sounds that surprised them. Compare what they say to their light and sound plans they made before they saw the show. You can end with a writing prompt asking the students to put their impressions in writing, including a closing evaluation of the importance of light and sound.