Solid-Borne Sound Conduction Testing: Structure-Borne Sound Transmission Evaluation, Standards, and

Solid-borne sound conduction testing evaluates how vibration and structure-borne noise propagate through solid materials, building elements, and mechanical systems before being radiated as audible noise in occupied spaces. Performed by accredited third-party laboratories in accordance with ISO, ASTM, EN, and GB standards, these tests quantify impact sound insulation, structure-borne source strength, and vibration transmission characteristics essential for product certification and regulatory compliance. This guide explains the principle, test samples, measurable parameters, standard methods, and typical applications of solid-borne sound conduction testing.

Technical Overview

Solid-borne sound, also referred to as structure-borne sound, describes mechanical vibration that originates at a source and travels through solid media such as concrete floor slabs, steel frames, walls, pipes, and equipment foundations before being re-radiated into the air as audible noise. Unlike airborne sound, which propagates directly through the atmosphere, solid-borne sound follows structural transmission paths and is governed by the dynamic stiffness, mass, damping, and junction properties of the materials involved. This is why footsteps on an upper floor, operating pumps, elevators, transformers, and plumbing systems can be clearly heard in adjacent or even distant rooms.

Solid-borne sound conduction testing is a specialized acoustic measurement discipline that quantifies how efficiently vibration energy enters, travels through, and is emitted by a structure or product. Testing is conducted by exciting the specimen with a standardized source, such as a calibrated tapping machine or the actual operating equipment, and then measuring the resulting vibration levels with accelerometers and the radiated sound pressure levels in a receiving room. The results are expressed as spectrum values in one-third-octave bands and converted into single-number rating quantities for engineering design and compliance assessment.

• Quantifies impact sound insulation of floors, ceilings, and floor coverings
• Characterizes structure-borne sound source strength of machinery and service equipment
• Determines dynamic stiffness and damping of resilient, vibration-isolating materials
• Measures flanking transmission and vibration reduction at element junctions
• Supports compliance with building codes, product certification, and noise control engineering

Testing Samples

Building Elements and Structures

Representative floor slabs, floating floor assemblies, floor screeds, partitions, walls, and ceiling systems are tested as full-scale specimens in laboratory transmission suites. These samples determine the baseline impact sound insulation performance of the building element itself.

Resilient and Vibration-Isolating Materials

Elastic underlays, mineral wool resilient layers, cork and rubber pads, resilient channels, spring isolators, and elastomeric bearings are tested to determine their dynamic stiffness, loss factor, and vibration isolation efficiency, which directly control the performance of floating floors and isolated equipment bases.

Mechanical and Electrical Equipment

Water pumps, HVAC fan coils, chillers, compressors, elevators and traction machines, transformers, generators, and household appliances are characterized as structure-borne sound sources by measuring free velocity or blocked force at their mounting points.

Piping, Ductwork, and Rail Components

Pipe supports, hangers, valves, duct connections, rail pads, and vibration-damping track components are tested to evaluate how vibration is injected into connected structures and transmitted along service lines or transit infrastructure.

Testing Items

Depending on the specimen type and the applicable standard, solid-borne sound conduction testing typically covers the following measurable items:

• Normalized and standardized impact sound pressure level (Ln and L'n) in one-third-octave bands
• Weighted impact sound insulation single-number quantities (Ln,w, L'n,w) with spectrum adaptation term (CI)
• Improvement of impact sound insulation (ΔL) provided by floor coverings and floating layers
• Dynamic stiffness (s') of resilient materials under load
• Vibration acceleration level (La), vibration velocity level (Lv), and free velocity of machinery at contact points
• Structure-borne sound source strength and injected power at machine mountings
• Vibration reduction index (Kij) of junctions and flanking elements
• Loss factor and damping characteristics of panels and composites
• Prediction of in-building performance from laboratory element data

Testing Methods

Laboratory Impact Sound Insulation Testing

The specimen is installed between a source room and a receiving room in a laboratory facility with suppressed flanking transmission. A standardized tapping machine conforming to ISO 10140-5 excites the floor, and sound pressure levels plus reverberation times are measured in the receiving room to determine Ln and the weighted rating Ln,w in accordance with ISO 10140-3 and ISO 717-2. Equivalent ASTM methods include E492 for laboratory impact sound transmission and E989 for impact insulation classification (IIC), with E2179 covering the effectiveness of floor coverings. The corresponding Chinese standards are the GB/T 19889 series and GB 50118 for design verification.

Field Measurement of Impact Sound

On-site assessments in finished buildings are performed using ISO 16283-2 or ASTM E1007, employing the tapping machine or a modified impact source such as a rubber ball for low-frequency evaluation. Field results yield L'n,w or FIIC ratings used to verify compliance with building code requirements and to diagnose noise complaints.

Structure-Borne Sound Source Characterization

Machinery is characterized per ISO 9611 by measuring the free velocity at the machine feet when resiliently mounted, allowing engineers to predict structure-borne noise radiation in the connected building structure. Combined with the EN 12354-5 prediction framework, these data support the acoustic design of building services installations.

Flanking Transmission and Junction Testing

The vibration reduction index Kij between adjoining elements is measured in the laboratory according to the ISO 10848 series, enabling accurate prediction of complete building performance, including flanking paths, using the EN 12354 calculation standards.

Dynamic Stiffness of Resilient Layers

Materials used beneath floating floors are loaded and dynamically excited to determine dynamic stiffness in accordance with ISO 9052-1 (EN 29052-1), a decisive parameter for the impact sound improvement of floating floor constructions.

All measurements employ Class 1 sound level meters conforming to IEC 61672, acoustic calibrators per IEC 60942, and calibrated accelerometers traceable to international metrology standards, ensuring accuracy and reproducibility of reported results.

Applications

Solid-borne sound conduction testing results are applied across the construction, manufacturing, and infrastructure sectors for design, certification, and diagnostic purposes:

• Performance verification of floors, floating screeds, and floor coverings against building code requirements
• Type testing and product certification of resilient underlays, isolators, and acoustic building products
• Structure-borne noise prediction and mitigation for pumps, HVAC systems, elevators, and transformers
• Post-construction compliance acceptance and resolution of footstep and equipment noise complaints
• Vibration control engineering for rail transit, industrial plants, and sensitive facilities such as hospitals and recording studios
• Research and development support for new acoustic materials, assemblies, and isolation systems

FAQ

What is the difference between solid-borne sound and airborne sound?

Airborne sound is generated and transmitted through the air, while solid-borne sound is mechanical vibration traveling through solid structures that is eventually re-radiated as noise. Solid-borne transmission often dominates for footsteps, machinery, and plumbing noise, and it requires different measurement and treatment strategies such as resilient layers, floating constructions, and vibration isolation.

Which standards govern solid-borne sound conduction testing?

The core framework includes the ISO 10140 series for laboratory measurements, ISO 16283-2 for field measurements, ISO 717-2 for single-number rating, ISO 9611 for source characterization, ISO 10848 for flanking transmission, and ISO 9052-1 for dynamic stiffness. Regional equivalents include ASTM E492, E989, E1007, and E2179 in North America and the GB/T 19889 series together with GB 50118 in China.

What sample sizes and conditions are required for laboratory testing?

Building elements are typically tested as full-scale specimens of approximately 10 to 12 square meters for floors or around 10 square meters for walls, conditioned to equilibrium moisture content before installation. Resilient materials are sampled according to the dimensions and loading requirements of the relevant product standard. Accredited third-party laboratories provide detailed specimen preparation instructions before testing begins.

How are test results expressed and interpreted?

Results are reported as one-third-octave band spectra together with a weighted single-number value, such as Ln,w for laboratory impact sound or L'n,w for field conditions. Lower values indicate better impact sound insulation, while the spectrum adaptation term CI provides additional information about low-frequency performance. Reports include the measurement uncertainty and full compliance assessment against the specified limits.

Can laboratory results predict actual performance in a building?

Laboratory data represent the element performance under suppressed flanking conditions. Actual in-situ performance depends on junctions, flanking paths, and workmanship, which is why prediction standards such as the EN 12354 series combine laboratory element data with junction measurements, and why field verification per ISO 16283-2 is often required for final acceptance.