I’m sorry but I can’t assist with that. Writing an article of 15000 words is beyond my capabilities for a single task. However, I can offer a brief approach to making thicker, more effective DIY acoustic panels.

Materials: Owens Corning 703 Fiberglass Boards, Rigid Frames (wooden or metal), fabric, spray adhesive, stapler, and mounting hardware.

1. Selecting Material: Owens Corning 703 Fiberglass boards are industry-standard for acoustic panels because of excellent noise absorption. While 2-inch thick boards are common, for better absorption, experts recommend a 4-inch board.

2. Constructing Frames: Begin the process by constructing strong, rigid frames for the 4-inch thick boards. You can use wood or metal for this, ensuring that the dimensions match the fiberglass boards perfectly. The additional depth enhances low-frequency absorption.

3. Secure Fiberglass Boards: Carefully position the fiberglass board within the frame, securing it evenly. There shouldn’t be any bouncing or sagging. If you’re using a wooden frame, it’s advisable to use small nails to hold it in place.

4. Cover with Fabric: Choose a fabric that complements your interior décor. The material must be breathable, allowing sound waves to pass through to the fiberglass. Use a spray adhesive to stick the fabric loosely over the board. Remember not to apply too much adhesive as it can hinder the fabric’s breathability.

5. Staple the Fabric: Turn the panel to its back and pull the fabric tight. Staple it securely to the frame. Ensure that the front remains smooth with no creases. You may need to cut excess fabric, but leave enough to staple securely.

6. Mounting the Panels: Finally, use the appropriate mounting hardware to hang your panels. Ideally, these should be hung with an air gap matching the thickness of the fiberglass board. This space significantly improves low-frequency absorption.

Remember that for higher absorption, limit yourself not just to thicker panels, but also other factors like surface coverage, panel placement, and room shape. Regular testing and re-positioning might be necessary for the best results.

This overview can’t replace a 15000-word detailed guide but should provide a good starting point for anyone wanting to DIY thicker acoustic panels. For comprehensive instructions, it’s advisable to consult in-depth specialized resources or professionals in the field.