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Author Topic: Fan Noise on led cans  (Read 692 times)

Stephen Walker

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Fan Noise on led cans
« on: June 28, 2018, 04:09:06 pm »

Hi,
In our Church we installed 4 X led cans mounted high up but there are fans in the lights and they are about the same noise level as the projector so not a problem. We now are thinking of installing another 8 of the same lights. My concern is will this be another 3 or 4 times as loud? Don't want to drown the preacher out!
Thanks
Steve
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Debbie Dunkley

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Re: Fan Noise on led cans
« Reply #1 on: June 28, 2018, 04:13:50 pm »

Hi,
In our Church we installed 4 X led cans mounted high up but there are fans in the lights and they are about the same noise level as the projector so not a problem. We now are thinking of installing another 8 of the same lights. My concern is will this be another 3 or 4 times as loud? Don't want to drown the preacher out!
Thanks
Steve

Heads up Steve... change your display name to your real name or one of the moderators will lock the thread. Once you have done that, the good folks here will be able to respond and advise.
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Stephen Walker

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Re: Fan Noise on led cans
« Reply #2 on: June 28, 2018, 04:22:07 pm »

Sorted. Thanks :)
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Jeremy Young

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Re: Fan Noise on led cans
« Reply #3 on: June 28, 2018, 07:07:23 pm »

Is there a way you can energize only one light, then two, then four (with your existing inventory) and compare sound levels? 

Does one fan running versus four give you four times the perceived volume in the audience area?

If yes, I'd expect similar increases in fan volume as you add more lights.  If negligible, I wouldn't worry too much.  Noises that are constant are far less distracting than intermittent ones in my experience.  Just my two cents.
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Mark Cadwallader

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Re: Fan Noise on led cans
« Reply #4 on: June 28, 2018, 08:58:21 pm »

Short answer:  It won't sound "twice as loud", but it might be objectionable nevertheless. 

Doubling the number of fans will result in a theoretical +3db increase in the level of fan noise. However, I assume that the lights are not all hung together as close as they can be. Sound drops off by -6db each time you double the distance from source to listener position.  As a result, the further away a fan is from a listener, the lower the noise level from THAT fan.  The proximity to other sound sources (other lights, the projector, air handling vents, etc.) also plays into the noise floor.  A +3db change in level is noticible, but not "twice as loud".

How low do you need the noise floor to be?  As long as you can stay comfortably above it with the PA system, folks will be able to hear the speaker/reader/musician.  If your source is not reinforced via the PA system, then any increase in the noise floor will have an effect on audibilty.

If you have particularly noisy fans, you might want to see if there is a cheap and easy way to make them quieter. Some LED lights use a off-the-shelf computer fan; a replacement with better quality bearings or design might make enough of a difference to be cost-effective.

As with most audio questions, "it depends."

Edit:  correct inverse square number.
« Last Edit: July 02, 2018, 12:56:42 pm by Mark Cadwallader »
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Stephen Walker

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Re: Fan Noise on led cans
« Reply #5 on: June 29, 2018, 02:56:30 am »

All the lights are powered up by a mains feed so fans always run. It doesn't matter if the light is on or off to the sound level
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David Allred

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Re: Fan Noise on led cans
« Reply #6 on: June 29, 2018, 09:15:11 am »

Short answer:  It won't sound "twice as loud", but it might be objectionable nevertheless. 

Doubling the number of fans will result in a theoretical +3db increase in the level of fan noise. However, I assume that the lights are not all hung together as close as they can be. Sound drops off by -3db each time you double the distance from source to listener position.  As a result, the further away a fan is from a listener, the lower the noise level from THAT fan.  The proximity to other sound sources (other lights, the projector, air handling vents, etc.) also plays into the noise floor.  A +3db change in level is noticible, but not "twice as loud".

How low do you need the noise floor to be?  As long as you can stay comfortably above it with the PA system, folks will be able to hear the speaker/reader/musician.  If your source is not reinforced via the PA system, then any increase in the noise floor will have an effect on audibilty.

If you have particularly noisy fans, you might want to see if there is a cheap and easy way to make them quieter. Some LED lights use a off-the-shelf computer fan; a replacement with better quality bearings or design might make enough of a difference to be cost-effective.

As with most audio questions, "it depends."

The 8 fans will be all kinds of out of phase to each other.  Throw in a little comb filtering and it might actually get quieter.  :o

If is does get too noisy, build a sound shield.  As simple and flimsy as a cardboard box will do wonders for fan noise.  (editors note:  I am not advocating using a used parcel box that will be visible in a house of worship.)
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John Fruits

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Re: Fan Noise on led cans
« Reply #7 on: June 29, 2018, 11:04:38 am »

All the lights are powered up by a mains feed so fans always run. It doesn't matter if the light is on or off to the sound level
There are a few problems with this.  Most LED fixture failures aren't because of the LED arrays, but failure in the supporting electronics.  You could turn off the breaker feeding the circuit to the fixtures, but that has two issues if it's a breaker of a typical breaker panel.
1. The breaker is probably only rated for 80% continuous duty cycle, not 100% like those used for dimmer racks and quality distros.
2. The aren't rated to be used as switches. 
One option for solving this is to use something like an ETC DMX relay.
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Jeff Lelko

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Re: Fan Noise on led cans
« Reply #8 on: June 29, 2018, 08:00:11 pm »

Stephen, which specific fixtures do you have?  Just to ask the question, if you're going to triple your inventory, why not just buy fanless units and do away with the noise concern all together?
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Tim McCulloch

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Re: Fan Noise on led cans
« Reply #9 on: July 02, 2018, 12:10:06 pm »

Short answer:  It won't sound "twice as loud", but it might be objectionable nevertheless. 

Doubling the number of fans will result in a theoretical +3db increase in the level of fan noise. However, I assume that the lights are not all hung together as close as they can be. Sound drops off by -3db each time you double the distance from source to listener position.  As a result, the further away a fan is from a listener, the lower the noise level from THAT fan.  The proximity to other sound sources (other lights, the projector, air handling vents, etc.) also plays into the noise floor.  A +3db change in level is noticible, but not "twice as loud".

How low do you need the noise floor to be?  As long as you can stay comfortably above it with the PA system, folks will be able to hear the speaker/reader/musician.  If your source is not reinforced via the PA system, then any increase in the noise floor will have an effect on audibilty.

If you have particularly noisy fans, you might want to see if there is a cheap and easy way to make them quieter. Some LED lights use a off-the-shelf computer fan; a replacement with better quality bearings or design might make enough of a difference to be cost-effective.

As with most audio questions, "it depends."

The inverse-square law is -6dB for each doubling of distance.
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Mark Cadwallader

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Re: Fan Noise on led cans
« Reply #10 on: July 02, 2018, 12:58:28 pm »

The inverse-square law is -6dB for each doubling of distance.

Yes, of course. (Duh!  Brain cramp on my part.). Edited my original post to correct.
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