When we have HDD or tapes that require blanking/wiping/clearing, instead of noisy shredders or software eraser, we use the Verity Systems SV91M Degausser.
This is a NATO approved degausser.
A degausser sends magnetic pulses of 7000 guass through the media to erase it in approx 12 seconds.
For information on the SV91M follow https://www.veritysystems.com/uk/products/sv91m/ 
