Carpet padding

[Alien]

Has anybody ever tried using some type of carpet padding for acoustic control, like a bass trap? Did it help?

 

[Zing]

While I think it would mildly help with the highest frequencies, I have to believe it would do absolutely nothing for low frequencies.

 

[Razz]

Good question.

One of the best sounding rooms I ever had carpet and a thick pad. I would think it does just like wall panels.

 

[yromj]

If enough of it used it may work as a bass trap ala some kind of insulation in a bag. However, the thickness of the individual pieces is still going to be fairly small (<1") and the ability of the individual pieces to transfer the movement to each other may make it less than ideal. My initial reaction is to stick with we know works because it's going to take a large volume of whatever is used.

John

 

[Flint]

Carpet padding is not a good acoustic absorber, though it is better than nothing at all. For less money and less material used fiberglass, mineral wool, cotton batting, and open-cell foam are vastly superior.

For example: (doing some research turned this up)

You can use a 1" thick piece of Owens Corning 703 compress fiberglass has an NRC absorption coefficient of 0.70 (absorbing 70% of the sound). Thick carpet has an NRC of 0.25 and thick carpet with heavy padding designed to be acoustically effective (the more expensive type) has an NRC of 0.50. The fiberglass is significantly more effective.

I cannot find verifiable NRC data on carpet padding alone, and with hundreds of different types out there it would be hard to find any accurate data on what you are asking about anyway. However, several "experts" in acoustics claim the NRC for thick carpet padding layered to be 1" thick is around 0.30. If accurate, then OC703 is 233% more effective when used in the same thickness.

As such, I don't believe I would waste any time trying to treat specific problems in a room with carpet padding. You are much better served with foam (Auralex, Sonex, and others), OC703 (Auralex ProPanels, RPG, GIK, others), or Mineral Wool (though messy and less rugged).

 

[Razz]

It might not be as efficient... however, if you are carpeting the whole floor as compared to a couple 2 foot x 4 foot panels the total amount of floor space covered should have just as much impact, if not more.

Now, that doesn't take into account first order reflections and such but over all it should make an impact.

 

[Towen7]

I got the impression that the OP was asking about using carpet padding as a wall treatment; for 1st reflections and bass trapping. Of course covering the entire reflective floor space will add some absorbency. That absorbency (and diffusion from the carpet itself) will likely cover only a narrow band of high frequencies though.

 

[Flint]

It might not be as efficient... however, if you are carpeting the whole floor as compared to a couple 2 foot x 4 foot panels the total amount of floor space covered should have just as much impact, if not more.

Now, that doesn't take into account first order reflections and such but over all it should make an impact.

As T7 pointed out, the original question was about acoustic treatments specific for HT use, not covering the floor.

However, while covering the floor with an average quality acoustic absorber will make a room less ambient and more "dead" and "boomy" sounding, it does not result in the best acoustical space for ideal sound reproduction. As I have mentioned many times and as every acoustic engineer has learned, the most ideal reproduction environments have wood floors. Reflections off the walls are much more important to treat than floor reflections, and covering an entire floor with a very limited bandwidth absorber hinders the performance across the overall audio spectrum. What's more, our spacial recognition skills are horizontal in nature, so front, side, and rear reflections are very significantly more important than floor or ceiling reflections.

We all have to live within the limitations we impose on ourselves for aesthetics and "style" when it comes to room acoustics, but carpet is rarely a good answer if one has allowed themselves the application of effective wall treatments.

 

[Alien]

I was just curious because I had some carpet padding that seemed to be rubberized, over 10X6 feet. Rolled up tight to have an ID about 4" it makes it almost a foot thick from the inside. So I just moved it into one of my corners and it made a negligible but noticeable difference. That was at least easier than trying to dispose of it anyway!

 

[Flint]

In that case, keep it there. A modest improvement is better than no improvement at all.

 

[Yesfan70]

.......Reflections off the walls are much more important to treat than floor reflections, and covering an entire floor with a very limited bandwidth absorber hinders the performance across the overall audio spectrum. What's more, our spacial recognition skills are horizontal in nature, so front, side, and rear reflections are very significantly more important than floor or ceiling reflections.....

Picking your brain a bit, but if the side reflections are that much more important (which I agree with you on), then what is the difference with carpet vs hardwood floors with a huge rug? I'm guessing treatments that would benefit the most would be the walls, ceiling, and then the floor in that order. If I'm right, I would think deciding to go with either carpet or hardwood floors purely from a sound quality concern would fall into that point of diminishing returns.

 

[DIYer]

The effect of carpet on the entire floor was posted on our old forum. It's called "comb filtering". Due to the thickness, it only absorbs down to certain frequency thus leaving lower frequency unaffected. This too can create dull sound.

 

[Flint]

.......Reflections off the walls are much more important to treat than floor reflections, and covering an entire floor with a very limited bandwidth absorber hinders the performance across the overall audio spectrum. What's more, our spacial recognition skills are horizontal in nature, so front, side, and rear reflections are very significantly more important than floor or ceiling reflections.....

Picking your brain a bit, but if the side reflections are that much more important (which I agree with you on), then what is the difference with carpet vs hardwood floors with a huge rug? I'm guessing treatments that would benefit the most would be the walls, ceiling, and then the floor in that order. If I'm right, I would think deciding to go with either carpet or hardwood floors purely from a sound quality concern would fall into that point of diminishing returns.

As DIYer pointed out, covering an entire floor, a very large portion of the reflective surfaces in a room, with a single poor performing acoustic absorber results in a very large portion of the ambient sound in the room at specific frequencies being deadened to the point of being too much. Basically, the overall RT60 of the room will show a fast decay in the upper midrange and treble, but the lower midrange and bass will not be affected at all. Then, when you attempt the address side, front and rear reflections - those which are the most important to control for very effective sound reproduction - you will be forced to use absorbers which ALSO absorb in the midrange and treble as well as the upper bass. That means the RT60 in the midrange and treble will drop off extremely fast making the room seem overly dead and "vaccuous" in the midrange and overly boomy in the bass where the RT60 remains long and strong.

So, if the ideal for accurate and enjoyably reproduction is a room with extremely well controlled front, side, and rear reflections across a broad spectrum which ALSO has a smooth & balanced RT60 across the entire spectrum, then once you treat the walls with absorbers and diffusors it would be detrimental to also have a ton of midrange absorption covering the entire floor.

Add to that the fact that furniture and other furnishings placed on the floor help with bounce echo between the floor and ceiling, and adding a simple wool area rug on a hard floor between the speakers and listener will darn near solve for any reflection based comb filtering in the mid-treble range, then having a hardwood floor is a MUCH better option (assuming you are treating the walls to the best of your ability).

It is NOT an issue of deminishing returns when the whole room will be completely dead when you treat the walls AND have plush carpet with a thick pad installed. The carpet hinders the appropriate use of wall treatments.

 

[Yesfan70]

That makes sense. Thanks guys for the explanation.

 

[Razz]

Yeah, thx, I remember going over this before but, as most things, memory is fading...

 

[jamhead]

Alien-

Who's that in your avatar?

 

[Zing]

Alien-

Who's that in your avatar?

Twenty bucks says that's Alien herself.

 

[Huey]

Alien-

Who's that in your avatar?

Twenty bucks says that's Alien herself.

Twenty bucks says you're wrong. I can't remember what he went by over at S&V, but he was the one whose daughter had the heart transplant.

BTW Alien, how is your daughter doing?

 

[jamhead]

That's correct Huey. And the only reason I ask is that she has a strong resemblance to his little girl, if I remember his old avatar.

 

[Alien]

That's my wife Kristyn...that photo actually, sofi helped take it! She hit the shutter.

She's doing great, as it looks from the outside anyway. Plenty of energy...too much sometimes. No heart function problems, never a sign of rejection. We actually just brought her back last week from her annual full checkup with biopsy, cardiac catheter, EKG, echo and x-ray. She seems fine but they found a coronary aneurysm they don't know the cause of and her left atrium is enlarged. They also check blood EBV (epstein-barr virus) level because immune suppressed people can get high levels of it that causes B-cell lymphoma. Hers has been elevated for a while. Normal immune system response it just causes mono.

Next week they're looking into the heart thing more to see if there's something needing to be done. Till then she's busy being a princess!