A workshop can be noisy despite thick walls. Sound passes through the partition, doors and ducts, and some of the energy is transmitted by structural vibration. A mineral wool panel is one element of an acoustic solution. To choose it sensibly, you need to distinguish between limiting sound transmission and reducing reverberation within the room itself. A conversation through the wall requires a different approach from the pulsing of a compressor. In an instrument repair workshop, noise can disturb the person at the desk even though it is slight outside. Note which equipment is running, for how long and where the sound is troublesome. This gives you a starting point for selection.