by T.R.T. Nightingale, J.D. Quirt and M.A. Sultan

sorbing material is pushed aside so it does not cover the box, thus only partially blocking the path between the outlet boxes (see Figure 1, Displaced Insulation); 3. Walls with the sound-absorbing material in the cavity completely covering the back of the outlet box (Figure 1, Fitted Insulation), so sound must travel through the sound-absorbing material to get to the other box. The electrical outlet boxes, each with a duplex outlet, plastic faceplate and all wiring necessary to simulate typical field installation, were positioned in three different ways: 1. Back-to-back, with zero horizontal offset (Figure 1, Back-to-Back Condition) 2. Within the same stud cavity, with a horizontal offset of 350 mm (Figure 1, Same Stud Cavity Condition) Effect of Electrical Outlet Boxes on Sound Isolation of Gypsum Board Walls The findings and recommendations pertaining to staggered and singlestud assemblies were in fact similar to those for double-stud assemblies. The effect of electrical outle