Pump is anything BUT quiet!
593817
The "quiet" air pump that comes with this set is VERY LOUD. It hums and rattles even when buried in foam. Very sad since we need quiet in our therapy rooms.
2679874
I bought this pump to replace the one in my office fountain which died after about 8 years.

It doesn't look quite like the picture but that doesn't matter.  It fit into the required space and connected to the existing tubing.  There were several other connective options in the package which I didn't need.

On the lowest setting it moves the water up approx 2 1/2 feet and spills it over the top.  MOST IMPORTANTLY, it does so silently!
1679381
Not super silent but definitely quiet for sure. And for the price, and for such a small product, it seems to be pretty good. Other air pumps I have used in the passed had a lot of vibrations but this does not; at least there are no vibrations I can hear.

I will have to see how well it performs in the long run but for now, it is perfect for my 10 gallon freshwater tank.
461851
I bought one of ShurFlo's current-generation pumps not realizing that it didn't have the variable-speed feature provided in a previous generation to reduce noise wehn water flow was low. As a result, the new pump was far noisier than I'd expected it to be. I inserted one of these hoses coiled in a loop right at the outlet of the pump, and it made a startling difference in the amount of noise from the pump.

I didn't find it necessary to use the second hose at the pump inlet, so am retaining it as a spare.
2442236
Very Noisy. The pump itself isn't the noisy part. The plastic reservoir tank vibrates against the base when it's hooked up. If I squeeze it tightly it is quiet for bit. The noise is very annoying. I've owned it a little over 24hrs and I don't think I can deal with the noise.
4091008
The pump works okay from a functional perspective, but it is noisier than I like.  I ended up replacing it with an Aquaclear powerhead pump, which while more expensive is much quieter and has a similar flow rate for my CO2 system.  I would recommend skipping this low cost pump if you care about having a quiet pump.
4386226
This pump is noisy for being so small.  I can hear a ticking sound from a few feet away.  The flow is right for my 20 gallon.  And I like that you can adjust it.  But I'm returning it.
4765935
Quieter than the FiTech pump I had before this. Definitely buy the extra Oring fitting when ordering.
1392557
Changed out the stock fans on my NZXT Kraken for two of these. With the case fans off I thought I had forgot to plug them in, the water pump was making more noise... they are completely silent at idle unless you have your ear two inches away. Even at full speed they make half the noise that the stock fans did at 70% speed. I highly recommend them if you want a silent build... hope to see what the airflow series can do in the future.
872465
I returned this air pump immediately.  The noise was unbearable.  "Whisper" is not part of this product's make up.  The air output was sufficient, but the noise it emitted could not make up for this.  Fortunately, Amazon's return policy is excellent so Amazon gets five stars but this pump gets one.
4882740
I purchased two of these pumps and connected them to a Hydor Smart Wave Circulation Pump Controller. While the pumps are running they are quiet and seem to move lots of water. However, the pumps make a VERY loud *Click* every time the wave-maker turns them on, and can easily be heard from across the room. These pumps are nice, but would recommend against any sort of stop and go application.
3003785
The machine cools efficiently, but it is incredibly noisy. When the compressor kicks in, there is no chance of sleeping or of hearing tv, etc. Noisier than any machine I've ever owned. I would never go near this brand again.
3247674
It cools the CPU well, but the pump does make more noise than I was expecting. It's not obscenely loud, but if you are looking to make a silent build you may want to look elsewhere.
3553895
Package was received timely and in excellent condition. The pump was as pictured and described, however the airstones and check valves that were supposed to be included were missing, the air tubing was included. I added the pump to power an 18" bubble curtain in the back of the tank. Using Both outputs on Max setting, there is poor volume of bubbles. I replaced the cheap tubing included with a quality tubing I had from a previous purchase thinking there could be a kink or blockage, but no improvement. After about a week, I replaced this pump with a cheap, single output pump from Walmart rated for a 10 gallon tank, and it produces twice the amount of bubbles. The pump works, and is very quiet, but just lacking in output.
3498256
My wife purchased this the other day in order to replace a cheap old DC bike pump we had that the valve connector broke off of. I had no idea that it was also designed to fill inflatable boats! I have a 15.5' Zodiac FC470 (Former Navy SEAL boat), and have been looking for an inflatable pump to use with it forever that wouldn't break the bank (avg. prices are $100-150). This thing filled it to maximum pressure in roughly 15 mins! For an electric pump, I didn't find it loud at all. In fact I thought it to be rather quiet.  After fully inflating my craft to it's maximum pressure the pump wasn't even hot. This thing didn't even break a sweat. I couldn't be happier to know that I've got a capable, solid inflatable boat pump for so little!

Yes, of course it does car tires, bike tires, pool toys, basketballs, etc,. But I'm floored about it working on my Zodiac!

Update: Burned out after a few months sadly.
3475448
Good, quiet pump my only negative is this model only has one output so a divider valve or T is necessary to go to multiple air-stones.
Overall this is a very quiet pump and puts out a good amount of air !
118761
I myself found this pump to be very quiet.  I use it for transferring cooled water to a distillation kit.  Though I'd say the pressure is only good enough for one ditsill kit it works just fine.  The - and + signs do decrease and increase the rate of water flow respectively.  Unless you're using it under close observation the amount of flow change may not be noticed.  Overall, for the price you can't beat it.