I tried the hot glue technique...it only muffled it slightly. The only way I found that was 100% effective was to take some pliers and surgically remove the PC speaker.  It works like a charm.

You can easily remove the speaker with a pair of needle-nose pliers. Just twist the speaker back and forth a few times and it will eventually come out. It's worthless for me anyway...I removed the speakers out of all 28 of my miners with no problems.

So I did a little experiment with one of my Antminer S3+ units (One of the better performing ones that is able to hold any frequency setting for long durations without any 'Xs.' I essentially tested out each of the frequency settings and compared them to the wattage numbers used at that setting with 110v power, then tested again at 230v.  The results of my testing are below:

http://i.imgur.com/3MZa9r0.jpg?1

In essence, what I found was somewhat obvious...that you get better Joules/Gh at 230V than you do at 110V, regardless of the frequency the miner is set to.  I also found that the 'sweet spot' of energy used per GH/s is around the 200 MHz mark (200 MHz @ 230v and 206.25 MHz @ 110v.)  I noted that in green, which incidently was the only reading that matched the 'published' efficiency numbers.  A few notes about my testing:

1. I left each of them at the specific MHz frequency for exactly 3 hours, then recorded the Wattage and Average hashrate at that time. I was off by a few minutes sometimes, but suffice it to say I left them for at least three hours. I did note that this number is more accurate the longer you wait...however, I didn't have so much time to play with this, so there may be some variation that I couldn't account for or the numbers may change more significantly over time.

2. I used the same Antminer for every setting, the same PS (Corsair CX750 with all four PCI-E cables plugged in) and the same Kil-a-watt unit for each test.  I was using the 8/11 firmware on the unit with the updated cgminer version (4.6.0-140908) posted by ckolivas.

3. The one major variable I couldn't control for was ambient air temperature, which was generally about 5C warmer in the 230V location than in the 110V location, plus during the day there were fluctuations. This likely would affect efficiency, though probably not by too great of a deal.

4. I used three variables which you don't see here...the price per kilowatt/hour ($0.10,) the current price of BTC in USD ($351.59,) and the amount of BTC/Gh/day based on difficulty (0.00001398 currently)

5. I included the power usage of the unit above when it is not hashing (noted as 0) just to note the overhead that the system takes up if it is on but not running.

Anyway, hope you can get some use out of this...at a minimum it taught me that it's not just a myth that 230V is more cost-efficient than 110V, but when it comes down to it, it's only more efficient by 1 or 2 cents a day...

Wow, thanks! You have a good point about the newer firmware...since these are S3+ units I'm on the latest rev, which doesn't respect the settings in the asic-freq file. Does anyone know a way to change frequency in the latest firmware without using the GUI?

Thanks for the detailed response...this may be beyond my current coding abilities but I've been meaning to learn this stuff more so I may take it on as a challenge anyway. I'll post if I can get it working...

Well, I used to program my TRS-80 many years ago and do some work in PowerShell automation, but I wouldn't say I'm proficient at all. Was hoping there was a fairly easy way to automate, but I can research what you noted above, thanks!

So....long story short, I have a total of Eighteen S3+ Antminers that are in a building that for most of the time is not used.  Every once in a while, however, it is used, so I want to be able to easily drop the fan noise down via a scripted approach. I have Teamviewer access to a live system there and I've used Putty to SSH into individual miners to change frequency on individual units. What would be a good scripted approach to change them en masses from say 250M to 212.5M and back?  Sequential IPs and all same username/PW...

Thanks in advance!

Batch 10 just showed up on Bitmain's site...at least the price is right for ROI.

http://i.imgur.com/SPOSNBA.png

They should give you a tracking number and it should be no more than a few days. My shipment is schedule to arrive in two days...

UPS shows my scheduled arrival time for this Friday afternoon between 2:15pm and 6:15pm PDT...will crack open one of these, post pics, and metrics too once I get them. It's Christmas in September!

FYI, my Batch 8 S3+ order just shipped roughly 6 hours ago. My order time was 2014-08-13 19:15:19.0. Ten days early isn't too bad I guess...thanks Bitmain!

Keep in mind that if you direct connect the ethernet cable you'll need a crossover cable or a special crossover adapter like this one for that to work properly. http://www.amazon.com/Cables-Unlimited-Cat6-Crossover-Adapter/dp/B00030BYJI/ref=sr_1_10?s=electronics&ie=UTF8&qid=1409967632&sr=1-10

Yeah, the sink isn't used...so we should be good to go. Needed a fresh outlet and an exhaust window for some more S3s so figured the laundry room would fit the bill.

How to launder Bitcoins easily.

http://i.imgur.com/RMq4MQf.jpg

My first B8 order should be one of the first to be processed (2014-08-13 19:15:19.0) so (one would assume) it should be one of the first to ship as well. I'll post in this forum immediately after receiving notification of shipment. Watching it like a hawk now...

Don't hold your breath, the 'Edit' link on my first B8 order disappeared weeks ago.

They changed the way that you change the frequency in the latest firmware. Instead of modifying the asic-freq file (which it appears to ignore now) you now instead make the changes via the 'Advanced Settings' tab in the 'Miner Configuration' area of the console.

That happened to me too, after the firmware upgrade it automatically changed me from stock 218.75 to 237.5 and the hashrate went down to 100 Gh/s with the frequency not showing up in the console. If you change it to 218.75M or 250M in Advanced Configuration, however, it goes back to mining at rates you'd expect at those frequencies. For whatever reason the upgrade switches it to 237.5 and it simply doesn't work.

Interestingly enough, if I SSH into the box, the asic-freq file shows me running at a different rate than the Advanced Settings tab and the status page show. Whatever they did in the firmware upgrade apparently bypasses the asic-freq file to make the changes. In any case, I have my four 'well-behaved' miners running at 250W now, and the two trouble children that don't OC well running at 218.75 on the new firmware and all seems fine for now. But agreed, the firmware update didn't seem to help much and makes me a bit nervous now.

Thanks! I broke down and ordered twelve more of the S3+ models that went on sale as part of Batch 8. Suffice it to say they won't fit into this bathroom though...I'll be putting them into a custom built room in a property I own that I previously used to host twelve of the S1s. That should give me at least 8 Th/s by the end of September.

And this is how you convert an old bathroom into a 2.6 Th/s antminer S3 farm. 

https://eesx0q.bn1.livefilestore.com/y2m8cId5TQ9xfY-agtYrGO-LA23xL36vET3oUeb2T0Go9S9iDsYscHNmthd_MYl4Q6id9gCFoV6sCWRbgdFGWl4yZaVWrF0UOo551Jz_V0Mc82rh852b_5TL-eU9fqQDQcP/ToiletMiner%20-%20Small.jpg?psid=1

All six miners and Corsair 750W PSUs exhaust out the back window. Fresh air is drawn through a cracked window on the opposite side of the bathroom. Each miner is stable at 218.75 stock frequency and averages 440 Gh/s per miner. 39C-40C average temps on each. I opted for one PSU per miner as I may decide to OC and got a good deal on them.

May never ROI at my electricity rates but I'm more of a hobbyist anyway...and this was a fun project.