Impact Sound Insulation Testing – Impact Noise Measurement Laboratory Services

Impact sound insulation testing measures the ability of floor and ceiling assemblies to block noise generated by impacts such as footsteps, dropped objects, and moving furniture. Conducted in accordance with international standards such as ISO 10140-3, ISO 16283-2, ASTM E492, and GB/T 19889, this testing provides quantitative data on normalized impact sound pressure levels for building products and completed constructions. Accredited third-party laboratories deliver these results to support product certification, building code compliance, and acoustic performance optimization.

Technical Overview

Impact sound, also known as impact noise or structure-borne noise, is generated when an object strikes a building element such as a floor. Common sources include footsteps, chair dragging, dropped objects, and household appliances. Unlike airborne sound, impact energy is introduced directly into the structural element and radiates into adjacent spaces below, making it one of the most frequent causes of noise complaints in multi-story residential and commercial buildings.

Impact sound insulation measurement quantifies how effectively a floor system attenuates this structure-borne noise. A standardized tapping machine is placed on the floor under test, and the resulting sound pressure levels are measured in the room below using calibrated microphones and real-time analyzers. The raw data are then normalized to account for the sound absorption characteristics of the receiving room, producing the normalized impact sound pressure level.

The measurement is typically performed across one-third octave bands from 100 Hz to 3150 Hz, with extended low-frequency and high-frequency ranges available for specialized applications. A single-number rating, such as the weighted normalized impact sound pressure level, is derived from the spectrum to allow straightforward comparison between floor assemblies and against regulatory limits. A lower value indicates better impact sound insulation performance.

Testing Samples

Laboratory Floor and Ceiling Assemblies

Full-scale floor specimens, including concrete slabs, timber joist floors, and composite steel-concrete decks, are installed in the test opening between a source room and a receiving room of a purpose-built acoustic laboratory. The specimen dimensions are typically around 10 to 12 square meters to ensure representative boundary conditions.

Floor Coverings and Finishes

Floating floors, engineered wood flooring, laminate flooring, ceramic tiles with resilient layers, and carpet systems can be evaluated either individually on a reference floor or as complete built-up assemblies. For floor coverings, the improvement of impact sound insulation is determined by comparing measurements on a bare reference floor with measurements after the covering is installed.

Resilient Underlayments and Impact Insulation Products

Elastomeric mats, cork layers, mineral wool boards, and other resilient interlayers are tested on a standardized concrete reference floor to characterize the improvement value they provide. This data is essential for manufacturers declaring acoustic performance in technical datasheets and environmental product declarations.

Completed Buildings and Field Conditions

For field measurements, the existing floor-ceiling separation between vertically adjacent rooms in a finished building serves as the test object. Field testing accounts for real construction conditions, flanking transmission, and workmanship, providing a realistic assessment of in-situ acoustic performance.

Testing Items

Impact sound insulation testing programs typically include the following measurable parameters:

• Normalized impact sound pressure level in one-third octave bands (laboratory, per ISO 10140-3)
• Normalized and standardized impact sound pressure levels (field, per ISO 16283-2)
• Weighted normalized impact sound pressure level, the primary single-number rating per ISO 717-2
• Spectrum adaptation term for the tapping machine spectrum
• Spectrum adaptation term for heavy and soft impact sources evaluated with a rubber ball
• Improvement of impact sound insulation of floor coverings
• Reverberation time in the receiving room, used for normalization calculations
• Background noise levels and associated measurement uncertainty
• Impact Insulation Class rating per ASTM E989, derived from field measurements per ASTM E1007
• Low-frequency extension measurements from 50 Hz for lightweight timber floors prone to low-frequency impact issues

Testing Methods

Laboratory Measurement Procedure

Laboratory testing follows ISO 10140-3 and its national equivalents such as GB/T 19889. A standardized tapping machine, consisting of five hammers driven at a rate of ten strikes per second with a specified fall height and effective hammer mass, is positioned at multiple locations on the test specimen. Calibrated microphones placed at several fixed or rotating positions in the receiving room below record the time- and space-averaged sound pressure level in each frequency band. The reverberation time of the receiving room is measured using the interrupted noise or integrated impulse response method, and the normalized impact sound pressure level is calculated by correcting for the room's equivalent sound absorption area.

Field Measurement Procedure

Field measurements follow ISO 16283-2, which superseded the earlier ISO 140-7 methodology. The tapping machine is placed in standard and additional positions on the floor of the upper room, including positions near walls where excitation of edge modes may increase sound transmission. Sound pressure levels are measured in the lower room, with low-frequency bands below 100 Hz measured using corner microphone positions per the standard's specific requirements. Results are normalized by the measured reverberation time and reference absorption to yield the normalized impact sound pressure level, and background noise corrections are applied where necessary.

Evaluation of Heavy and Soft Impacts

For sources such as children jumping or objects being dropped, a standardized rubber ball may be used as an additional excitation source in field measurements. The resulting maximum sound pressure levels are evaluated, and the spectrum adaptation term provides a supplementary single-number descriptor that better correlates with subjective response to low-frequency impact noise in lightweight constructions.

Rating and Data Processing

Measured one-third octave band spectra are converted to single-number ratings in accordance with ISO 717-2. The rating curve is shifted relative to the measured spectrum until defined deviation criteria are satisfied, yielding the weighted value. In North American practice, the Impact Insulation Class is computed per ASTM E989 using a similar curve-fitting approach applied to data obtained per ASTM E1007. The final test report presents band-by-band results, single-number ratings, measurement setup details, instrument calibration status, and uncertainty statements.

Applications

• Certification and declaration of acoustic performance for flooring products, underlayments, and resilient layers
• Compliance verification against building regulations specifying minimum impact sound insulation for multi-unit residential buildings
• Green building certification schemes and sustainability documentation requiring verified acoustic data
• Research and development of new floor assemblies, floating floor systems, and vibration-isolation products
• Diagnostic investigations of noise complaints between vertically adjacent occupied spaces
• Quality control on construction sites, verifying that installed floor systems meet design specifications
• Comparison of competing products and support for procurement decisions based on verified laboratory data
• Input for acoustic simulation models used in building design and performance prediction

FAQ

What is the difference between impact sound and airborne sound insulation?

Airborne sound originates from sources that radiate into the air, such as speech or music, and must pass through the building element as an airborne wave before being re-radiated. Impact sound is structure-borne: mechanical energy is injected directly into the floor structure by a footstep or impact and travels through the material before radiating into the room below. The two phenomena are measured with different excitation sources, different metrics, and different rating procedures, which is why they are assessed separately.

Is a higher or lower weighted impact sound pressure level better?

A lower value is better. The metric describes the sound pressure level measured in the room below when the floor is excited by a standardized tapping machine; a lower transmitted level indicates superior impact sound insulation. Conversely, when evaluating floor coverings by the improvement value, a higher value is better because it represents greater noise reduction added by the covering.

Can laboratory results predict performance in a real building?

Laboratory results characterize the floor assembly itself under idealized flanking-free conditions. In actual buildings, flanking transmission through walls and other connected elements, workmanship quality, and junction detailing typically reduce the achieved performance relative to laboratory values. Field measurement per ISO 16283-2 is therefore recommended for final verification of completed constructions.

How should samples be prepared for laboratory testing?

Specimens should replicate the complete floor buildup intended for real installation, including structural slab, screed, resilient layers, adhesives, and finishes, with representative dimensions matching the laboratory test opening. Conditioning to equilibrium moisture content is required for hygroscopic materials. Test plans should define edge boundary conditions and installation procedures, as these strongly influence measured results.

How long does an impact sound insulation test take?

A single laboratory measurement on a prepared specimen is typically completed within one working day, including instrument calibration, tapping machine positioning, level and reverberation time measurements, and data processing. Field measurements in occupied buildings generally require several hours per floor pair. Report issuance follows internal review, typically within five to ten working days after testing.