dBA (noise) question

stomachmonkey · 03-03-2011, 02:41 PM

OK, lets say I have a device that has fans and the decibel level is 66.

If I replace the current fans with two rated at 36 dBA what's worst case total dBA.

In theory if they are in sync I could end up with 72 dBA total?

Or theoretically I could hang a fan speed controller on one and get them out of phase so they cancel each other out?

Educamate me.

david914 · 03-03-2011, 02:45 PM

39 dB

red-beard · red-beard's Garage

David is correct

Hugh R · 03-03-2011, 02:52 PM

39, yes. Sound pressure/level doubles for a little less than every 3 dB increase.

stomachmonkey · 03-03-2011, 02:53 PM

Quote:

Originally Posted by david914

39 dB

Serious?

Thanks.

Second question I just thought of, do dB's rise linear or logarithmic?

Is 60 dB twice as loud as 30?

stomachmonkey · 03-03-2011, 02:54 PM

Quote:

Originally Posted by Hugh R

39, yes. Sound pressure/level doubles for a little less than every 3 dB increase.

Awesome, an answer before I post another question.

Love this board.

So 66 is way louder than 39.

Hugh R · 04:29 PM

66 dB isn't all that loud. The 8-hour worker Time Weighted Average (TWA) allowable by OSHA is 90dB, but with an action level where if you're exposed to 85 and above (which is less than 1/2 of 90dB) then the employer has to test your hearing annually and take administrative control, such as sound deadening, and personal protective equipment (ear plugs or muffs) and make sure year-to-year your hearing doesn't experience a "threshold shift" at different frequencies.

If you have an iPhone download the app "DJ app" or "Paul Von dyk" it has a crude but useful soundlevel meter and a frequency meter.

red-beard · red-beard's Garage

For computer equipment, 66 db is like a chainsaw...

65 is an electric hand mixer

Dishwasher 50-53

A quiet office 20-30

stomachmonkey · 03-03-2011, 03:54 PM

Quote:

For computer equipment, 66 db is like a chainsaw...

It's a dual Xenon 1U so yeah that fkr is loud. Making me nuts. Problem is there is no where to hide it in the house.

Looking at some fan alternatives. Hate to have to pick up a board in ATX and swap everything over to a different case.

Red88Carrera · 03-03-2011, 03:58 PM

My honda EU3000iS generator runs between 49-58 dBA.

RWebb · RWebb's Garage

dB - not db or DB or Db

the reason is that the B means a Bell

and the d means deci-

yes it's a log scale

there is likely a real pretty graph with icons for various examples on the internet somewhere

it may have more annoyance impact than the increment from 36 to 39 tho - depends on location of listener & source + any reflective or absorptive surfaces in the area (not to mention standing waves)

Eric Coffey · 03-03-2011, 04:30 PM

Quote:

Originally Posted by Hugh R

39, yes. Sound pressure/level doubles for a little less than every 3 dB increase.

Not exactly. In acoustic/audio applications, a 3db increase only represents a doubling of the power. Twice the sound pressure level is closer to 6db. Twice the perceived "loudness" (volume) is actually closer to 10db.

red-beard · red-beard's Garage

Quote:

Originally Posted by stomachmonkey

It's a dual Xenon 1U so yeah that fkr is loud. Making me nuts. Problem is there is no where to hide it in the house.

Looking at some fan alternatives. Hate to have to pick up a board in ATX and swap everything over to a different case.

What size fans are in the case? Look at Newegg for some low noise, high flow fans. I did this recently for my drafting machine. This helped a bit. Swapping out the power supply helped even more. It is not perfectly quiet, but much much better. If I moved it back under the desk, I would never even notice it.

The CPU fan and the video fans are what I can't change...Well, I can change the CPU fan, but they are expensive! I can switch off the cooling control and let the fans spin up and the difference is huge.

Hugh R · 03-03-2011, 04:35 PM

Eric I believe you're correct. I'm a little rusty on the subject and used the terms interchangeably which is incorrect.

RWebb · RWebb's Garage

I'll start a computer case fans thread...

imcarthur · imcarthur's Garage

Quote:

Originally Posted by Eric Coffey

Not exactly. In acoustic/audio applications, a 3db increase only represents a doubling of the power. Twice the sound pressure level is closer to 6db. Twice the perceived "loudness" (volume) is actually closer to 10db.

Correct. If you really want to dive into it, here is a calculator page where you can input values for sound pressure to loudness level etc: Sound level change and the loudness ratio

Ian

stomachmonkey · 07:59 PM

Quote:

Originally Posted by red-beard

What size fans are in the case?

8 of those little bullet fans, 4 rows of 2.

This is the best replacement option I've found.

Would require 2 of them.

Thermaltake 1U Intel Xeon Server Solution 1U Active Solution Copper CPU Cooler for Socket 604: A1934 (Retail)

MysticLlama · 03-03-2011, 08:23 PM

Yup, those 1U cases with those things are brutal.

If it's an OEM box, they are probably only running at half speed too.

I know my HPs spin up to full (and deafening) and then throttle down to half once the test is done. This way they know they can kick up to double if one dies. And you'd know it as soon as they did.

peppy · 03-04-2011, 07:36 AM

This is the graph they use for my son.

stomachmonkey · 03-04-2011, 07:44 AM

Quote:

Originally Posted by MysticLlama

Yup, those 1U cases with those things are brutal.

If it's an OEM box, they are probably only running at half speed too.

I know my HPs spin up to full (and deafening) and then throttle down to half once the test is done. This way they know they can kick up to double if one dies. And you'd know it as soon as they did.

OEM Dell, does the same thing, starts up with fans full speed then throttles them back. But even half speed they are loud.