NRC STC Sound Ratings Explained in Detail (dmitry-demidov)

STC Vs. NRC Sound Ratings and What do they Mean?

Most people have heard about sound ratings or sound levels. These are used to measure the loudness of sounds. Sound Ratings indicate what is known as the "sound level" or "Sound Pressure Level" (SPL), which is measured in decibels. The SPL is related to the ability of the human ear to detect sounds. The higher the SPL, the greater the ear's capability to perceive and identify the sound. The level of SPL is usually expressed in units such as dBA. However, a normal conversation has a sound pressure level of 70 to 80 dB. This is the SPL required for a person to speak comfortably in an average-sized room.

What is Sound Rating?

Sound Rating is the standard the National Institute of Standards and Technology (NIST) uses to measure the intensity of noise in the air and water. Sound Ratings help you decide whether the product is suitable for your use or not. You must wear hearing protection when using loud products like a hair dryer, lawn mower, and chainsaw. Several different Sound Ratings are available. The level at which noise is considered dangerous is 110 dB. Anything above 120 dB is very loud and causes damage to your ears.

Familiar Sources of Noise and Decibel Levels

 A whisper is about 30 dB, normal conversation is about 60 dB, and a motorcycle engine running is about 95 dB. Noise above 70 dB over a prolonged time may damage your hearing. Loud noise above 120 dB can cause immediate harm to your ears. (Source: CDC Govt. platform)

Plain Acoustic Panel Design (monstera)

History of STC Sound Ratings and How they Evolved. Also, STC Ratings and How they Made it Through!

STC is a product's sound rating, and NRC is a product's noise rating. Both ratings are determined by the National Institute of Standards and Technology (NIST).

STC ratings provide a qualitative measurement of how soundproofing materials perform. STC ratings were first developed in 1978 by the U.S. Department of Housing and Urban Development. These ratings, intended initially for government-assisted housing, are now used by real estate professionals, architects, and building owners to select soundproofing materials. These ratings have remained unchanged since the inception of the system.

STC is a subjective rating that reflects the effectiveness of a soundproofing product when installed as an interior or exterior wall treatment.

There are three levels of Sound Transmission Class:

STC 1 – 25 dB

STC 2 – 35 dB

STC 3 – 50 dB

In addition, there is a fourth rating category for products unavailable in the U.S. (or discontinued). STC 4 – 75 dB is reserved for products not listed on the STC scale.

For example, typical two-inch-thick drywall is rated STC 3.0 for the U.S., meaning it has a sound transmission class of 30 decibels. The higher the rating, the better the insulating effect of the soundproofing material. If you wanted to compare the sound of a power saw to the sound of a lawnmower, it wouldn't be fair to say one is louder than the other, but it's pretty easy to imagine the lawnmower being louder than the power saw. In this example, the relative dB values would be almost identical.

Regarding safety, Lp is a common choice because it's more consistent. An Lp value of 75 indicates the average person can hear someone speaking at 75 feet away at an average conversational volume.

Historically, soundproofing materials were rated for their effectiveness by STC. However, the soundproofing industry began to standardize ratings. Today, two primary sets of standards are used to determine soundproofing quality: the ASTM E90 test for construction sound control and the NRC Sound Rating for Sound Reduction for interior sound control.

NRC stands for Noise Reduction Coefficient. The lower the number, the better, and it is the number most commonly found in sound reduction specifications and ratings.

For example, a 1-inch thick double wall with 2 inches of concrete in between is considered a "4" STC. This would be an excellent choice for a residential garage. It provides enough sound reduction for a typical garage but not enough to prevent hearing damage from a long car ride in a busy neighborhood.

A 1-inch thick single wall with 2 inches of concrete in between is considered a "3" STC. This is ideal for a medium to a large apartment or commercial building that might have a car in it. The concrete helps to block some noise, but the wall isn't strong enough to withstand an enormous vehicle impact or loud music. It would be adequate for a small office or hobbyist workshop, but a more prominent home would require a better wall to keep sound from seeping through.

A 1/2-inch thick single wall with 2 inches of concrete in between is considered a "2" STC. This is adequate for a bedroom or small apartment with a vehicle in it. If the concrete is dry laid, you can use less material to achieve the same results.

The thickness of the walls and the type of insulation that is used in the wall are two things that determine the amount of sound reduction. Several types of insulation are used for this purpose, including fiberglass batts, spray foam, rock wool, cellulose or cellulose blocks, mineral wool, fiberglass blanket, and cellulose panels. Each type of insulation is different and has advantages and disadvantages.

A 3 STC is not sufficient for a home where music is played loudly, or there is a car with loud music. These buildings require a 4 STC (STC stands for Sound Transmission Class, as labeled above) for the interior.

In homes, the walls are the most common sound barrier. The walls in our homes are usually made of wood or plaster, depending on the house. These materials can cause noise to leak through. If the walls are made of dry wall, this is a good choice for a small room where noise can't escape. If the walls are made of brick, stone, or concrete, this is a good option if you want to insulate against sound. A 4 STC is required for a large home with a car, music, or loud conversations. You should consider installing double-glazing if you live in a large house with many windows. This is made of two panes of glass sealed together. An even cheaper and more popular (wink wink!) option these days is noise reduction panels made of a timber frame with varying layers of acoustic foam. Bubos is a Triple-Certified brand name, so rest assured you are in promisingly safe hands! We have also been labeled as the best Home Theatre artistic acoustic panel brand by our competitors.

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