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Sound Transmission and Flooring Types

When it comes to flooring, the more muffled the sound, the better, especially in a multi-story building, house, apartment, or condominium. Fortunately, there are several good flooring choices with effective sound dampening properties.

Sound is transmitted when hard objects, like hard-soled shoes, furniture, dropped objects, or even dog claws impact a hard surface, like tile or stone. Without anything to absorb it, sound waves can spread, multiply, and echo off the walls, amplifying even a small sound to a distracting crescendo with the right acoustics. Given a large room with high ceilings and hard polished floors, a simple walk across the lobby of an office building, for example, can become quite a distraction.

Sound Ratings

Sound transmission is rated using three different standards, each defining a different way in which sound is transmitted. Sound absorption of floor coverings may be measured on two of those scales. The third covers room-to-room transmission, more appropriate for walls.

IIC (impact insulation class) is measured in terms of sound impact, or how well sound vibrations travel through a floor to the room below.

IIC 50 has the least impact sound absorption quality. While this may be appropriate for ground floors, it would be unsatisfactory for most on a high floor without a great deal of insulation in the area between the floor and the ceiling below. Most stone and tile will fall into this category.

IIC 60 indicates a medium impact sound absorption quality and encompasses floorings such as wood, laminates, and some vinyls.

IIC 65 is a high level of impact sound transmission absorption and includes superior sound reduction materials like carpet and cork.

IIC is greatly influenced by the surfaces and areas under the floor and the IIC rating can be significantly enhanced by the addition of underlayment, insulation, or by floating the floor. The “loudest” floor is stone or tile laid directly over concrete. The IIC scale does not account for joist noises like squeaking or rattling.

NRC (noise reduction coefficient) measures the amount of noise that is absorbed by the material and not reflected. A room with a high NRC rating would eliminate background noise and echoes to help clarify speech. Theaters, for example, must be constructed to have a high NRC rating. Without it, sound waves would bounce off the walls and crash into each other, creating a cacophony of continuous sound, making individual words impossible to distinguish. Carpet, with an NRC rating of .40–.50 is the most efficient absorptive material. Vinyl, cork, and rubber have a fairly high NRC rating, with hardwood, bamboo, tile, and stone at the bottom of the scale for sound absorption.

Under the Floor

Sound transmission is affected by more than just the top layer of flooring. Other factors include the underlayment and subfloor, plus adhesives and sealants used during installation. If used on a higher floor in a multi-story structure, insulation between the floor of one room and the ceiling of the room below plays an important part in deadening sound. Any kind of insulation packed between the joists will not only help to trap and dissipate sound, it will block the loss of heat or air-conditioning, effectively lowering your utility bills.

Installation Materials

The use of flexible acoustic adhesives adds yet another layer of sound dampening properties to the floor. Applied around the edges of the floor, a flexible sealant is designed to fill gaps where the floor meets the wall or around doors or air ducts in order to block channels where sound can travel.

Flooring for Sound Reduction

Carpet

Number one on the on all counts is carpeting. By definition, carpet is the antithesis of hard, echoing surfaces. Sound waves are effectively absorbed and deflected by the carpet and by the padding under the carpet, and the level of sound absorption can be enhanced with a thicker pad. Carpet is usually the cheapest option in the short run, but also the most problematic in terms of durability, cleaning, and allergy aggravation because it tends to trap allergens and dust.

Cork

Cork is a great choice for sound reduction. It does more than merely dampen sound; it absorbs it, creating a blissful peace that everyone will appreciate, including downstairs neighbors. Cork is such an effective sound reduction material that it is used on walls to soundproof recording studios to produce clear soundtracks without background noise. The key is in the porous structure of the cork. Rather than bounce around, sound waves sink into the cellular structure of the cork and are broken up.

In addition to the obvious benefit of sound reduction, cork flooring adds natural warmth to rooms and a slightly springy give that makes it comfortable and easy to walk or stand on and may even save dropped objects from breaking on impact.

Vinyl

Quality vinyl flooring that is backed with foam and has a cushioned, flexible surface, makes it a good choice for a sound reduction, but as with everything else, you get what you pay for. While you can install any tile over an existing floor, the material of the floor will influence sound absorption qualities. Top quality vinyl will help nullify that factor and provide a nearly soundless surface that has spring and give for comfort.

Laminate

Laminate flooring can be a reasonably good choice for sound reduction with the addition of a quality underlayment. In addition to absorbing sound, a layer underlayment will add a feeling of solidity to the floor and reduce the hollow percussive sound that footfalls can produce when laminate flooring is floated over a subfloor without the benefit of underlayment. The underlayment pads a laminate floor much in the same way that a pad works under carpet, adding give for extra comfort and insulation for overall warmth.

(43) Comments

  1. Be careful with adding an additional underlayment. You mention the flooring has an attached underlayment. I was told by Home Depot that you can damage the floor by adding additonal underlayments as it doesn’t lay properly when it already has one attached. I used engineered hardwood and added a high sound resistant padding from Wisteria Lane. I have a very grumpy lady below me who complains about everything and I have not had a complaint (knock on wood) but I also use area rugs, not large ones but runners and place small rugs here and there. I also have a 55 lb dog and a 11 year old granddaughter.

  2. We are considering a vinyl product for flooring a 3rd floor condo. It is called Coretec Plus and has a cork backing with IIC 62db and STC 62db. Because the flooring that has been used in other condos in the condo complex includes carpet, tile and manufactured wood, the HOA requires an underlayment – but are not specific re the ICC or STC. They say, “if the neighbor below complains, you may be ask to remove the flooring.”
    The manufacturer says a 1/4″ cork underlayment can be used with Coretec Plus but is usually not needed and is certainly not required by manufacturer. Do you feel we need to spend an additional $1000 for cork underlayment? What we want to use is new to the complex but there is cork under vinyl, it is simply attached. Thanks for your response.

  3. I am installing 5 MM vinyl plank flooring on an above grade concrete slab. The salesmen recommend Tranquility acoustical underlayment that is also a vapor barrier. An old-timer told me to use roof felt as an underlayment. I was considering laying the felt down and the factory underlayment over that, in order to provide extra sound and insulation capabilities. What is your recommendation?

  4. I need to replace carpet on the second floor which makes noise when someone walks on it.
    I do not want to have carpet again. I would like to remove the noise and trying to cover the second floor
    to be clean and no noise. What do you suggest?

  5. Margo W / David S - Reply

    Recently my son purchased 1400 feet of engineered hardwood. After laying a hallway and bedroom, we have quite a bit of squeaking noise. Before finishing the other 900 feet, what can be done to keep to help quiet this irritating noise? The natural acacia wood looks great, but the sound is not at all acceptable. Besides returning the product, is there a secret to silence the wood?

  6. I am considering a wood laminate floor with insulation already attached to be instaledl in a condo high rise that requires 50 fiic. Is a per attached insulation adequate?

  7. We’re laying 3/4 soft mahogany solid wood over Elastalon layer over original 60s intact 8″ vinyl over concrete. Does the vinyl add to the ST number? Elastalon falls a little short of coop rules.

  8. Will the addition of cork underlayment along with a 3 mm underlayment help with sound absorbtion? What thickness of cork underlayment is best? Going on concrete slab 6″.

  9. l want to purchase rolls of 3/8 cork rolls. to put down under tile on my 5th floor condo .
    I have been told all l need to do to lay it is to clean the concrete floor, put a bonding agent on the concrete allow to dry then unroll the cork apply underneath the cork to the floor with a thin layer of the same thin set I am using on top of the cork to set the tile. Is this the correct procedure???????do I install one row of cork and tile at a time. Instead of 2 or 3 rows of the cork. I’m concerned about the cork wanting to roll up at the ends!!!!!!

  10. Im replacing the floor in the Bath w/ cork , I’ve been told that the only option I have is to apply the flooring with glue and not the floating floor, My thinking is if I seal the perimeter and put a good water resistant barrier/underlayment to keep the sub floor dry this should be sufficient ( I quit splashing in the tub some time ago) so water on the floor is minimal , is this feasible ?

  11. I was wondering if you could help? Does engineered floating with a 14mm gap wooden floors make more noise or less than tiles ( with no additional isolation)?
    I ask as I believe the wood floors that are floating by 14mm would make less but I am being told tiles do

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