The Secret Behind Perforated-Panel Sound Absorption: Why Can’t Quiet Spaces Do Without This “Breathing” Panel?

Today, in many public buildings—such as gymnasiums, exhibition halls, underground spaces, and even some schools—observant visitors may notice that the walls and ceilings are fitted with panels riddled with tiny perforations. Upon inquiry, it becomes clear that these perforated panels possess a remarkable property: they can effectively “absorb” noise.

Today, we’ll take a closer look at a star material in acoustic decoration—perforated acoustic panels—and uncover the core principles behind their sound‑absorbing and noise‑reducing performance.

As is customary, let’s start with the question: why do perforated acoustic panels absorb sound and reduce noise?

Many people used to blow into empty bottles as children; when you blow across the mouth of an empty bottle, you can hear a deep “buzzing” sound. This phenomenon is known as Helmholtz resonance. The column of air at the bottle’s opening acts as the neck, while the space inside the bottle forms a cavity. When you blow across the mouth of the bottle, both the neck and the cavity vibrate together, resonating at a specific frequency and converting acoustic energy into heat, which is then dissipated.

The principle behind perforated‑plate sound absorption is to arrange countless “small bottles” in a row. Each tiny hole and the cavity behind it forms a miniature resonator; when thousands upon thousands of these resonators are neatly mounted on a wall, and a sound wave whose frequency happens to match their natural resonance arrives, they all vibrate, rub against one another, and generate heat—thereby dissipating the sound energy.

When it comes to sound absorption, it’s important to clarify one key distinction: sound absorption is not the same as sound insulation. Sound absorption primarily targets the noise source—for example, installing acoustic panels in a room helps dissipate the noise generated within that space. In contrast, sound insulation prevents sound from passing through walls or floors, blocking its transmission across spaces. It works both ways: it keeps indoor noise from escaping and outdoor noise from entering.

In practical applications, sound-absorbing materials are used to reduce noise and minimize indoor reverberation, while sound-insulating materials are employed to prevent sound from propagating across spaces. Only by combining these two approaches can a quiet environment be achieved.

When applying acoustic panels to reduce noise, it’s essential to identify the frequency of the noise source and then select a perforated panel that resonates near that frequency; only then will the sound‑absorbing performance be optimal. The resonance frequency of a perforated panel is primarily influenced by four factors: perforation ratio, hole diameter, panel thickness, and back‑cavity depth. We won’t delve into the detailed calculations here—those are purely technical—but interested readers can explore them on their own. For now, we’ll focus on the frequency range and provide an overview of the corresponding perforation ratios.

Perforation rate is the key factor determining sound‑absorption performance. The principle behind perforated panels is straightforward: a cavity is left behind the holes, and when sound waves enter these openings, they induce vibrations and friction within the cavity, converting acoustic energy into heat and dissipating it. Typically, perforated panels have hole diameters of 3–8 mm, cavity depths of 3–10 cm, and panel thicknesses of 5–10 mm. Meanwhile, the perforation rate—defined as the ratio of the total area of the holes to the panel’s overall surface area—directly determines which types of noise the panel can effectively attenuate:

In short: For open spaces, a high perforation rate is recommended; for equipment rooms, a low perforation rate is preferred; and for public areas, a medium perforation rate is appropriate. Of course, real-world applications are far more complex: in practice, perforated acoustic panels are often paired with porous materials such as glass wool in the back cavity to further enhance sound absorption in the mid‑to‑high frequency range. Additionally, increasing the hole diameter or deepening the back cavity can shift the absorption spectrum toward lower frequencies.

We know that perforated acoustic panels commonly used in everyday applications are, in the vast majority of cases, made from rigid materials such as calcium silicate boards or gypsum boards. This is primarily because many public spaces must balance sound absorption and noise reduction with safety requirements—preferably using Class A fire‑resistant materials—while also maintaining a degree of aesthetic appeal and decorative value. When considering any single criterion, it’s easy to find products that excel in one area but fall short in others; yet truly versatile solutions that meet all three criteria are relatively rare. Moreover, there’s another factor that owners cannot ignore: cost. Discussing materials without factoring in construction costs is a common practice among material suppliers, but it’s not necessarily what owners want—and this often ends up influencing their decision‑making.

It should be noted that some perforated panels have a semi‑perforated design, meaning the holes do not penetrate completely through the material. This configuration is commonly found in gypsum‑based products, such as high‑density composite ceiling tiles and decorative gypsum boards. The primary reason is that these materials lack sufficient structural strength; if fully through‑going holes were used, their mechanical integrity would be severely compromised, potentially leading to safety concerns down the line. Consequently, manufacturers opt for a semi‑perforated appearance that mimics the look of traditional perforated panels. However, such semi‑perforated panels offer very limited sound‑absorption performance. By merely replicating the visual style of perforated panels without delivering genuine acoustic benefits, they risk misleading consumers.

Traditional acoustic panel installation requires constructing a light‑steel stud framework to create an air cavity, partially filling the cavity with glass wool, and then applying perforated acoustic panels as the finish. This is the standard configuration: fully perforated panels backed by sound‑absorbing cotton within an air cavity. Nowadays, there are also new composite perforated panels that deliver more pronounced sound‑absorption performance than single‑material counterparts, such as fiberglass‑reinforced calcium silicate perforated panels.