If you landed here, you’re probably looking to solve a wall or ceiling soundproofing issue. Perhaps you’re wondering if it’s possible to achieve a 100% soundproof room.

Before diving into the specifics of soundproofing walls and floors, it’s crucial to understand what IIC (Impact Insulation Class) and STC (Sound Transmission Class) ratings mean. These ratings are essential in the world of acoustics, and they play a pivotal role in determining the soundproofing quality of different materials and assemblies. In this article, I will discuss the means to achieve proper soundproofing through assemblies and associated soundproofing components such as RSIC’s, Mass Loaded Vinyl, and Green Glue.

Introduction to IIC and STC Ratings

IIC Ratings: The Floor Focus

IIC ratings primarily refer to floor assemblies. They measure the ability of a floor to reduce impact noise – think of footsteps, dropped items, or moving furniture. Another way to look at the difference is to yell at a wall (airborne), versus tapping the wall with your finger (impact). The higher the IIC rating, the better the floor assembly is at insulating against impact noises.

STC Ratings: Wall Wisdom

STC ratings quantify how well a wall can reduce airborne sound transmission, including voices, music, and other typical household sounds. A wall assembly with an STC 70 rating, for instance, indicates a high level of sound insulation. STC ratings are used in both floor and wall assemblies.

How Are These Ratings Obtained?

Both IIC and STC ratings are essentially decibel ratings. They’re obtained through standardized tests that measure the decibel reduction provided by a wall or floor assembly. The process involves generating sounds of varying frequencies and intensities and then measuring how much sound is stopped by the assembly.

Are All Sound Frequencies Reduced by the Same Decibel Level?

No, not all sound frequencies are reduced by the same decibel level. The performance of a soundproof wall assembly can vary significantly across different frequencies. This is because lower frequencies (like the bass in music) are much harder to block or absorb than higher frequencies (like human voices). The rating given for a particular assembly is an average rating.

Therefore, an STC or IIC rating doesn’t necessarily provide a complete representation of an assembly’s performance across all frequencies. It’s essential to consider the specific frequency range when choosing an acoustical solution that will suit your needs.

Understanding Soundproofing When Building Wall Assemblies

Wall Assemblies: The Building Blocks of Soundproofing

Wall assemblies are the structural components that make up the physical barrier between rooms. They are composed of several layers of materials, where each plays a role in reducing the transmission of sound. The effectiveness of a wall assembly in terms of soundproofing is determined by its STC rating.

When aiming for an STC-70 virtually soundproof room, the selection and arrangement of the materials are of paramount importance. The assembly usually includes elements like drywall, insulation, and special connectors such as RSIC’s, Mass Loaded Vinyl, and Green Glue. Together, these components work in harmony to prevent the passage of noise, for the peace and quiet you desire.

Can a Room Be Made Soundproof?

Let’s consider a typical scenario requiring the need for a soundproof wall – a home theater room. This project is normally taken on after the home is built and requires special treatment of the walls that divide the theater room from adjacent rooms in order to reduce the transmission of voices and music.

Can the room be made soundproof? The simple answer is “yes!”, but there is another question that needs to be asked at the same time – do you need an STC-70 rating for your specific situation? Before we get to that, let’s look at factors that need to be considered to achieve the STC-70 rating.


Soundproofing, especially to high standards like STC-70 or IIC-70, can be a significant investment. Materials, labor, and the complexity of the installation process all contribute to the cost.


Proper soundproofing requires technical knowledge and expertise. This involves understanding acoustics, the specific needs of a space, and the most effective materials and methods for sound insulation.

Constructing a wall assembly that achieves an STC rating of 30-50 is within the average contractor’s normal experience. However, typical construction techniques are not suitable to achieve a higher rating, such as STC-70, when building a wall assembly.

This is not to say that regular contractors are incapable of building the wall, rather, the attention to detail required in ensuring the tightness of connections, and sealing of all openings is above average for the typical construction project.

Room Configuration

The physical layout and construction of a room play a crucial role in soundproofing effectiveness. Structural elements, room size, and existing materials all impact the feasibility and approach to achieving a virtually soundproof environment. In addition, consideration must be given to the amount of space that will be lost in constructing the soundproof walls.

A normal residential interior wall is 4-5″ wide. To achieve an STC-70 rating the new wall may be a total of 12″ wide, depending upon the final configuration needed. Can you afford to give up the extra space?

Typical Wall Assembly for an STC-70 Rating

Since an STC-70 rating is rarely required in a normal residential scenario, there are few examples available that provide detailed guidance. Here is a chart that shows the best scenario to produce an STC-64 rating:

The rating could be raised to 70 (or close to it) with the addition of Green Glue between the sheets of 5/8″ gypsum on both sides of the wall.

Another possible solution would be to build an additional wall with gypsum on one side that would be installed a 1/2″ from the existing wall, but removing the drywall from that layer. Basically, this would be one wall assembly, where the interior parts of the two studs would not have drywall or other type material. This would not only drastically increase the noise reduction capabilities of the wall, but will also provide a space to run electrical wiring and outlet boxes.

What is Required to Achieve an ICC-70 Sound Rating?

ICC ratings apply to floor structures, and very often the complete floor assembly is not available to the owner. If you live in a condo or other multi-floor residential unit, you will only have the surface of your floor to work with to deal with impact noise reduction.

The number one solution to noise reduction on your floor is to switch from hardwood or tile to carpet. Carpet provides a significant increase in noise reduction as it is soft and readily absorbs impacts, whereas hardwood and ceramic tile will transmit the sound to the structure below.

If you need to increase the noise reduction above and beyond the carpet, Iso-Step® products can help you achieve your goals.

Iso-Step® Floor Underlayment

Iso-Step® Floor Underlayment

These products range from 2mm to 12mm and the thicker the product, the higher its effectiveness, though it’s not in equal multiples. For example, a 6mm Iso-Step® product does not produce 3 times the effectiveness of the 2mm product, but it is still an improvement.

Potential Problems When Using Iso-Step® Solutions

The product is a great solution, however, it’s important to understand that an increase in your new flooring height could affect other areas in your home:

  • Doors – you may need to trim the bottom of your doors if they are binding on the materials.
  • A different toilet flange could be required.
  • Kitchen and bath cabinets may need to be raised.
  • Stairs may require adjustments.
  • Possible building code violations could result in certain circumstances.

Need to Boost Your STC and IIC Performance?

AudioSeal® MLV Soundproofing Barrier

AudioSeal® Mass Loaded Vinyl Sound Barrier

AudioSeal® Mass Loaded Vinyl Sound Barrier

The AudioSeal® MLV Soundproofing Barrier is a versatile sound reduction material that has been engineered to effectively block unwanted noise transmission through walls, ceilings, and floors. Constructed with a high-density, non-reinforced mass-loaded vinyl (MLV) that exhibits exceptional flexibility, it serves as a damping layer in your soundproof wall assembly. This product, when properly utilized, can enhance your STC rating, to help provide the extra decibel reduction needed to achieve an STC-70 or IIC-70 rating.

Do Most People Need STC-70 or IIC-70 Sound Rating?

While STC 70 and IIC 70 ratings offer exceptional soundproofing, they are often more than what is typically required in residential or standard commercial settings. The key is to balance the sound difference between two adjoining areas.

If the room that is producing the sound is at a decibel level of 80 db and the adjacent quiet room needs to be at 40 db, all you need is an STC rating of 40-50 to achieve a balance. This type of assembly is much easier and less expensive to build than an STC-70 wall.

Acoustical Solutions: The Premier Choice for Effective Soundproofing

Achieving STC 70 or IIC 70 soundproofing levels is possible, however it is often more than what is necessary for most situations.

Understanding specific soundproofing needs, based on the difference in decibels between spaces, is the key to selecting the right wall and floor assemblies for effective sound insulation.

This is where and when the team at Acoustical Solutions can help. We offer a range of products and expertise to help you achieve your desired soundproofing level, whether it’s for a residential, commercial, or industrial application.

Contact us today for more information!

To learn more about how Acoustical Solutions can solve your noise control problems, use our contact form, call one of our Acoustical Sales Consultants at (800) 782-5742, or visit us on the web at acousticalsolutions.com.