PPI, biy wax ci limu pax yi ci puus bu nekk, mooy benn jumtukaay ngir natt densité pax yi ci sponge.A PPI bu kawe dafay tekki ni pore yi ci sponge silicone bi dañuy gëna dëgër.
40ppi silikone sponge amna dayo pore bu gëna mag (di densité pore bu gëna suufe), permeabilité air bu gëna baax (liggéeyukaayu air bi dafay yokk ci 30% ba 50%), te yomb naa setal. Dafa baax ci senaario yi soxla permeabilite bu rëy wala setal bu bari, lu melni sistemu filtration air.
60ppi sponge, ndax pore yu dëgër yi (ak 50% ci densité pore yi), dafay gëna am solo ci wàllu isolation son (di wàññi 8-12dB) ak insulation termik (résistence termik yokk ci 20%-35%), moo tax mu méngoo ak ingénieur akustik wala aplikaasioŋu isolation tàngoor.