PPI, bivuga umubare wibyobo kuri santimetero, nigice cyo gupima ubwinshi bwimyobo muri sponge. PPI ndende bivuze ko imyenge iri muri sponge ya silicone iba myinshi.
Sponge ya 40ppi silicone ifite ubunini bunini bwa pore (ubucucike bwo hasi bwa pore), uburyo bwiza bwo guhumeka neza (kongera umwuka mwuka 30% kugeza 50%), kandi byoroshye kubisukura. Irakwiriye kuri ssenariyo isaba umwuka mwinshi cyangwa guhanagura kenshi, nka sisitemu yo kuyungurura ikirere.
Sponge ya 60ppi, kubera imyenge yuzuye (hamwe no kwiyongera kwa 50% mubucucike bwa pore), ikora cyane mubijyanye no gutondekanya amajwi (kugabanya urusaku rwa 8-12dB) hamwe no kubika ubushyuhe bwumuriro (kurwanya ubushyuhe bwiyongereyeho 20% -35%), bigatuma bikwiranye nubuhanga bwa acoustic cyangwa progaramu yubushyuhe.