Well, how hot does it get now, without the 'silencer'? If it is already 15 Celsius above ambient - forget it - it'll get too hot.
Otherwise, for US$ 10 (=279SEK) it's worth a try, but I strongly advice to keep an eye on the HD temp.!
Anyway - was your HD always as loud as now ? If no, back up your data and get a new one...
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