There are a number of excellent articles over on the website of the American Association of Community Theatre.
This is the fourth in a series of extracts from those articles and a link so that if you want to read more you can get to the entire article.
The fourth one is about the role of Sound Designer.
The sound designer plans and provides the sound effects in the play. The composer writes any original music the show may require.
All the music and/or effects in a play considered as a whole make up the "soundscape."
In addition to the sounds of the words spoken by the actors, a play may also call for sound effects to recreate lifelike noises or use music or abstract and unidentifiable sounds to support the drama.
The designer's work
Sound designers and composers begin their work by studying the script, gathering as much information as they can about any sound or music it calls for. As in all other aspects of design, an early meeting with the director and the design team is essential to get a clear understanding of the production concept.
Some directors will already have very clear ideas about what the sound effects and/or music should sound like, while others may request that the sound designer/composer sit in on rehearsals to assist with developing effects and music to fit the specific contexts in which they will be used.
Once they have a precise sense of what the production needs out of the music or sound, the composer begins composing the necessary musical pieces and the sound designer begins to gather and create the necessary sounds.
The complete article can be found here.