so many DASH coins  

That is just to close the holes till I get the other miners connected. (hot air coming through if its open)

I haven't done mining before but as a musician, I know how annoying soundproofing can be.  You could try soundproofing foam which is pretty cheap or, if you're more serious (e.g. you have A LOT of miners), you could always try getting the room properly soundproofed by professionals, but this could often cost over $10,000 unless you do it yourself.  If you're any good at handywork you could try setting up two walls and filling the gap with sand, which is a more traditional way of doing it.

Best way to sound proof your miners is to sell your Antminers and get some GPUs.

If you are willing to risk the adventurous path you could consider egg trays. Those are bejond "cheap" BUT not exactly that sort of fire resistant material. And your rig WILL puff some smoke one day. Pronounce dust ignition.
Top row on shelf can be plastic water bottles that melt & flow out if something bad happens. There are Liquid Packaging Plastic Bags of higher capacity and lower melting point.



I shouldn't really give hints on dirt cheap DIY stuff anymore.

i call them the "twins" almost finished while waiting for cpu to arrive. was testing if everything holds up & yes it does, no scrws were used on the risers & no cable ties were used for any of the cables.




finally parts arrived, completed & tested they run nice, delivered to customer, added voltmeter to them as a little appreciation due to slight delay of cpu.




side by side, almost 100% identical.



*p.s: this is NOT an ad as per some fellow members claims it to be an ad without any evidence showing that it is & was claimed that i was spamming my ads across forums & threads*

this is just to share my builds.

Here is my 7 GPU server case solution 

Low price.
7 satoshi. good times to buy

Wer macht mit? Habe bei 500 sats gesetzt.