Get something like this to filter the air intake:

https://smile.amazon.com/gp/product/B00AFRIVNQ/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Get two of these (Antminer shroud on Amazon):

https://smile.amazon.com/Antminer-120mm-Duct-Cooling-Shroud/dp/B01LXZ8EUG/ref=sr_1_1?ie=UTF8&qid=1517085678&sr=8-1&keywords=antminer+shroud

Get some 4" x 12 or 25' insulated ducting like this:

https://smile.amazon.com/gp/product/B00FK8RG0E/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

Get some 4" clamps or very long zip ties, or use both:

https://smile.amazon.com/gp/product/B0083GC8TO/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1  (much cheaper through homedepot.com or at the store)

Get something like this to filter the air intake:

https://smile.amazon.com/gp/product/B00AFRIVNQ/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

The either buy the cheapest cooler with thick stryofoam walls, or buy bins like these (under $10 for top and bottom at home depot):

https://www.youtube.com/watch?v=QMdiKm2tKPA

You'll need to do some rough measurements of the where the A3 sits and where its fan ports are when set inside the cooler/bin.

Then you'll need to get your drill out.  I used a 4 1/4 hole saw (Milwaukee tools but I don't think it matters).  Drill a pilot hole first (flip the hole saw and put the flat side against the bin/cooler to mark where the center needs to go.  Hold the drill with both hands, iron tight grip, and very lightly touch the plastic side of the cooler/bin.  If you don't grip the drill like a bastard, or if you press hard against the plastic, your drill will jump up and away which is dangerous.  Go lightly, lightly.  Only takes a second to drill your holes.  Sand the ragged plastic around the holes.  Hold your drill with both hands.

You need to drill a smaller hole closer to top side (one side only) to snake in your Ethernet cable + all power cables.  I put the PSU on top of the box; it's plastic, non-conductive and sturdy enough.

Put eggshell acoustic foam on the inside.  Or, I sprayed a bunch of 3M 90 and then brought two tiny rolls of pink fiberglass at home depot.  I stuck fiberglass under the lid using the 3M glue.  I put some fiberglass on the bottom, under the A3, when I lightly placed fiberglass on the sides and one more layer put loosely on the top.  Fiberglass cuts down sound better if you do not compress it.  Just put it lightly where it needs to go.

Shut the lid.

I didn't actually get my Antminer shrouds in time, so I don't have those in place, but the noise reduction is very, very good.  I've got my filtered air intake shroud right by a window opening so that it can suck in cool air.  

Youtube, type in "antminer silencer"

Use a cooler, or bins like the one show in this video https://youtu.be/QMdiKm2tKPA

Cooler method:  

https://youtu.be/HhNS2ElN5Mk

https://youtu.be/QfMrOjezl7k

https://youtu.be/iS5nqMvcLDo

https://youtu.be/1uA3c9fjOSc

Or, spend 2x 3x what the parts cost and just buy the same thing on ebay.

There are good YouTube videos on silencing Antminers.  Two options, use a cooler or just get a large plastic tub at Home Depot/Hardware store.  Use insulated ducting to suck air in and exhaust out.  Pack enclosure with fiberglass or acoustic foam.  Do put some type of filter on the air intake.  I had to scramble to get one put together yesterday but it really cuts down on noise.

I don't know, They're so loud I can hear it on the second floor from the basement. It's intolerable.

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569mhz - 787ghs

I turned down the frequency because I've lost 1 S9 board before and 1 avalon board

so with your temps I would get some kind of better air conditioning or venting