Selecting the correct material depends on the primary goal: sound absorption, soundproofing, or thermal retention. For acoustic needs, Open-cell Polyurethane foam or Rock Wool are excellent for absorbing echoes, while Mass Loaded Vinyl (MLV) is superior for blocking sound transmission. For heat insulation, prioritize Fiberglass, Aerogel, or Closed-cell Nitrile Rubber (NBR) due to their low thermal conductivity. Always verify the R-value for thermal efficiency and the NRC (Noise Reduction Coefficient) for acoustic performance.