A spatial sound-absorbing body is a sound-absorbing component that is suspended dispersedly in the upper part of a building space to reduce indoor noise or improve indoor sound quality. It features low material consumption, light weight, low investment, high sound-absorbing efficiency, flexible arrangement, and convenient construction. Many countries have been using spatial sound-absorbing bodies since the 1950s, and their application became increasingly widespread in the 1970s. In China, their application began in the 1970s and grew steadily in the 1980s.  

Based on a building’s usage purpose, area, floor height, structural form, decorative requirements, and sound source characteristics, spatial sound-absorbing bodies can be designed in various shapes, such as plate-like, block-like, cylindrical, conical, and spherical. Among these, the plate-like structure is the simplest and most widely used. Spatial sound-absorbing bodies are mostly used in indoor stadiums: their diverse shapes and arrangement methods enhance the indoor decorative effect, and most importantly, their sound-absorbing performance prevents echo defects in large halls and effectively reduces reverberation time.  

Compared with sound-absorbing materials applied on indoor surfaces, spatial sound-absorbing bodies have higher sound-absorbing efficiency under the same projected area. This is due to two key factors: first, spatial sound-absorbing bodies have a larger effective sound-absorbing area (including their top, bottom, and side surfaces); second, sound waves undergo multiple reflections between the top surface of the sound-absorbing body and the building’s ceiling, leading to repeated absorption. This increases the sound absorption capacity and improves overall efficiency, with the most significant improvement typically seen in the mid-to-high frequency range.  

Sound-Absorbing Performance  

The sound-absorbing performance of spatial sound-absorbing bodies is usually expressed by the effective sound absorption of a single unit at different frequencies. The effectiveness of spatial sound-absorbing bodies in reducing noise (or reverberation time) mainly depends on their quantity, suspension spacing, material, and structure, as well as the sound field conditions in the building space. For example:  

- If the original indoor surface has little sound absorption (resulting in excessive reflected sound and long reverberation time), suspending spatial sound-absorbing bodies can usually reduce noise by 5–8 decibels, with a maximum reduction of 10–12 decibels.  

- If the original indoor surface already has sufficient sound absorption (with no obvious reverberation), suspending spatial sound-absorbing bodies is unnecessary.  

Key Design Considerations  

1. Materials and Structure  

A typical spatial sound-absorbing body consists of a framework, a protective surface layer, and sound-absorbing filler. Material selection depends on the size, rigidity, and decorative requirements of the sound-absorbing body:  

-Framework: Wood, angle steel, or thin-walled section steel can be used.  

-Protective Surface Layer: Materials such as plastic window screens, plastic nets, steel wire meshes, and perforated panels (e.g., thin steel plates, aluminum plates, plastic plates) are suitable. Perforated panels should have a thickness of 0.5–1.0 mm, a hole diameter of 4–8 mm, and a perforation rate of over 20%.  

-Sound-Absorbing Filler: Ultra-fine glass wool wrapped in glass fiber cloth is commonly used. The filling density should be 25–30 kg/m³, and the thickness (5–10 cm) should be determined based on the frequency spectrum characteristics of the sound source.  

2. Suspension Quantity  

The number of spatial sound-absorbing bodies to suspend is calculated based on their sound-absorbing characteristics and the additional sound absorption required to reduce indoor noise (or control reverberation time). For plate-like spatial sound-absorbing bodies:  

- When their total area accounts for 30–40% of the building’s ceiling area, their sound-absorbing efficiency reaches its optimal level.  

- In practical projects, to meet noise reduction or reverberation control requirements, the total area of spatial sound-absorbing bodies is preferably 40–50% of the ceiling area. Increasing the quantity beyond this range will not improve overall sound-absorbing performance but will instead cause unnecessary cost waste.  

3. Suspension Method  

Most spatial sound-absorbing bodies are suspended from the top of the building space, usually hanging below the ceiling. Plate-like spatial sound-absorbing bodies can be suspended in three ways—horizontally dispersed, vertically dispersed, or a combination of horizontal and vertical—and all achieve roughly the same noise reduction effect when their total area is equal.  

-Height Requirement: For horizontally suspended plate-like bodies, the distance from the ceiling is generally 1/5 to 1/7 of the room’s clear height. In practice, suspending them below the steel frame of the ceiling usually meets this height range, satisfying both sound-absorbing and decorative needs. If conditions permit, they can be hung lower (closer to the sound source) for better performance.  

-Decorative Coordination: To enhance the architectural decoration effect, the shape, color, and suspension method of spatial sound-absorbing bodies should be comprehensively considered. Hanging them in artistic patterns and coordinating with lighting, ventilation, and overall interior design will further improve the overall effect.