Ok, so here is the next short article in the 5 gallon air conditioner - Does It Work series. The topic of this article is NOISE.
So, we here at 5gallonairconditioner.com constantly get asked, after "does it work" the next question is "how noisy is it?"
So, in this short blog post, I will talk about decibels, typical decibel levels, and simple facts.
A decibel is the unit scientists use to measure the intensity of sound. One odd thing about the decibel scale is that it's logarithmic. Now, don't let that scare you, logarithmic scales are very simple to understand.
Since the human ear is very sensitive to sound, scientists need a VERY BIG range to accurately measure sound intensity. For instance, when it is completely silent in a room, and you can hear your fingertips slightly rubbing against each other vs standing right next to a jet fighter airplane with full afterburner engines. That is a VERY BIG range of sound intensity that the human ear can hear, and so therefore, the decibel scale is logarithmic.
Think of a logarithmic scale this way, ADD ZEROS. So, for instance, total silence is 0 decibels. Then a sound (such as rubbing your fingers slightly together at 1 ft away from your ear, about the lowest the human ear can hear) that is 10 decibels, is 10X more powerful than total silence. So, in that case, you added 1 zero for 10 decibels.
So, now a sound that is 20 decibels, you ADD A ZERO, so that sound (rustling leaves in a slight breeze) has 100X more intensity of sound than total silence. So, think of the 2 in 20 decibels, as 2 ZEROS (100). So, 20 decibels is 100X more intense.
30 decibels is 1,000X more intense. (very quiet human whisper)
40 decibels is 10,000X more intense, etc. (very quiet library, rustling of books etc)
So, the loudest sound the human ear can hear before permanent hearing loss, is about 200 decibels.
Some decibel examples:
50 decibels - refrigerator compressor, car driving by at 50 ft, percolating coffee maker.
60 decibels - normal voice, dishwasher
70 decibels - vacuum cleaner, loud talking
80 decibels - alarm clock, doorbell, cake mixer
90 decibels - screaming, yelling, shouting
100 decibels - loud factory machines, airplane at 1000ft away
110 decibels - rock concert, chainsaw
120 decibels - police siren
So, here at 5gallonairconditioner.com, I have designed these AC units with a 64 decibel fan. Why you ask?
Performance of course! Oh yeah, and that nasty little thing called the laws of physics.
Think of sticking your head out of the window of a moving car. When the car is going 20mph, there is a sound of wind blowing by your ears. Now, theoretically, if you stuck your head out of the window while the car is going 70mph, that wind noise will be "a lot" louder. That's just simple physics.
So, again, it is a performance trade-off that must be made. I could design a "quiet" fan, but then the fan wouldn't move much air ( 20mph example above). Then you would be disappointed that "the dang thing doesn't blow enough."
So, then I design a "loud" fan, and the comment comes "this dang thing is too loud." But, in this case, what I don't hear is "this thing doesn't blow enough."
A normal "room size" fan sitting in the corner of a bedroom, a typical 20 inch 110V fan on the high setting is approximately 70 decibels, the low setting is about 55 decibels.
So, a fan, any fan that moves any noticeable amount of air, will make noise between about 50 and 70 decibels.
It's simple physics, the more air flow, the louder the sound, ie, stick your head out of a moving car example above.
Another question, we here at 5gallonairconditioner.com get asked a lot is, why not put in a bigger fan?
Again, the answer to that question is, "it's a series of tradeoffs" and "the line has to be drawn somewhere." There are much larger diameter fans that will physically fit, no question. The question becomes, which fan takes the least current draw (as discussed in a previous blog post) for battery life concerns, AND produces enough pressure to actually push the air out the ports and into the room/space, AND moves enough air volume to be effective, AND isn't cost prohibitive AND is DC powered for efficient off grid applications AND fits within the confines of a 5 gallon bucket AND is moisture resistant.
When I factored all of those valid concerns into the design, the result is a fan that makes 64 decibels of noise, takes about 4 amps of current draw, moves 250 cubic feet per minute of air, and has about 1.5 inches of water of pressure.
So, it's a series of trade-offs in the design.
But the final answer to the question, of "does it work?" is OF COURSE IT DOES!
And, to the question of, "how noisy is it?" About as loud as any other fan. Not as quiet as some, but quieter than others.
So, then the next question that get's asked is, "is there a variable speed model" available?
That will be the topic of the next article in the 5 gallon air conditioner - does it work series.