Typically, a metal deck is a structural material to withstand loads of gravity. However, there have been effective attempts to use decks for more than one purpose since it was first commercially offered. The acoustic deck is an application of decking material to serve several purposes at minimal extra cost. The acoustical deck provides the necessary horizontal and vertical load resistance together with a completed ceiling that can reduce noise.

Illustration of Miami Metal Deck disassembled

Learn About Acoustical Metal Deck

What Structures Usually Have This Metal Deck?

Controlling loud noises in transit station projects, theaters, sanctuaries, schools, power plants, natatoriums, museums, libraries, gyms, convention centers, churches, art galleries, arenas, and airport terminals can be achieved with the specifications of acoustical wall panels and acoustical floor or roof deck systems. 

How is Noise Reduction Achieved?

The acoustical insulation or substance, along with the perforations, reduces the noise. Through the openings in the deck, the sound enters and is absorbed by the soundproofing mechanism. There is a slight loss of stiffness and strength due to the perforations in the deck. The decrease in sound is between 5 and 10%. For the precise capacity or ability to reduce noise, speak with your deck provider.

The sound absorption figures at different frequencies for standard acoustic roofs or floor decks are acquired or procured by conducting the ASTM C423 test, with mounting corresponding to ASTM E795.

The fraction of noise that the tested surface transforms into other energy forms—which do not reflect as sound—is represented by the sound absorption ratios. Additionally, the usual testing frequencies lie between 80 and 6300 Hz. The noise reduction coefficient (NRC), rounded to the nearest 0.05, is the average of the coefficients for 250, 500, 1000, and 2000 Hz.

Moreover, the sound absorption coefficient for a specific frequency can be more than one due to measurement methodologies. Still, for any intended usage at that frequency, the value should be assumed to be one. 

The NRC and sound absorption at any given frequency are functions of the entire construction. In place of the frequently used foam board insulator, fiberglass insulation board can be utilized to achieve higher NRC values as the insulation material on the surface of the deck system 

For advice, speak with deck experts, but remember that the insulation board chosen for its thermal properties won’t have the same value as fiberglass board. In a gist, acoustical performance will be impacted if specific roofing components are substituted. 

What Is the ASTM C423 Test?

This test procedure entails monitoring the decay rate to determine the amount of sound absorption in a reverberation room. ASTM C423 test shows how to measure the sound absorption coefficients of a sample of sound-absorbing material, such as acoustical ceiling tile, as well as the absorption of a room, an object, such as an office screen, and a room.

Even though this test method focuses on laboratory measurements, it can be utilized to assess the absorption of rooms in the field.

What Is an NRC Value?

Acoustic absorption is frequently assessed using Noise Reduction Coefficient (NRC), which generates ratings ranging from 0.00 to 1.00. Measuring the potency of a square-unit of absorption measures a material’s capacity to either reflect or absorb sound. If your project has a larger surface area, thick materials with three-dimensional characteristics can have NRC values greater than 1.00.  

An acoustic metal deck gets a score of 0.00 if it reflects every sound that hits it. On the other hand, it gets a score of 1.00 if it completely absorbs all sound waves that strike it. The greater the acoustic performance you obtain from a specific product, the higher the NRC rating number.

Additional acoustics performance indicators include STC for sound transmission and SAA for sound absorption over various frequencies. However, because NRC focuses on sound absorption coefficients for the four fundamental frequencies of human speech—250 Hz, 500 Hz, 1000 Hz, and 2000 Hz—it has become the industry standard in design. For this reason, creating speech privacy and cozy shared spaces depends on proper NRC testing.

The majority of sound absorption materials are rated below 1. The uniform measurement of NRC across various product types may, however, frequently be difficult to assess since material testing techniques vary. 

Even within a single location, NRC rating evaluations differ from product to product. To make the best purchasing selection, it is crucial to comprehend how it is calculated and varies between products.

rusty Miami Metal Deck inside a warehouse

Reflection and Reverberation of Acoustical Metal Deck

Sound can enter the listener’s ear directly from the source or by surface reflection within a closed space. Likewise, the sound will often reflect as it bounces off different surfaces. A small amount of absorption occurs with each reflection, eventually reducing the sound.

Reverberation, however, can enhance the impact if the sound source is constant, such as a machine.

If you have more questions about the reflection and reverberation or anything about acoustical metal deck, please give us a call!