Soundboards, also known as sound boxes or resonators, are often used in musical instruments to amplify the sound. However, there are other synonyms that can also be used depending on the context. For instance, if you're referring to the sound system of a recording studio, then mixing boards or audio interfaces might be a better fit. Alternatively, if you're talking about a woodworking project, you might use the term noise barriers or acoustic panels. Sound absorbers or diffusers could also be appropriate. At the end of the day, the word you choose will depend on the specific situation and what you want to convey.