A standard impact test gives us something valuable: a controlled source that can be repeated from one floor to another. But the neighbour below does not live under a test machine. They hear footsteps, running, jumping, furniture movement and objects falling—events with different forces, rhythms and frequency content.
Why standard sources matter
Building-acoustic tests need repeatability. A standard tapping machine applies a known sequence of small impacts, allowing the receiving-room level to be compared against a requirement or between constructions. Without a controlled source, it would be difficult to separate the floor's performance from the person making the sound.
In England, Approved Document E uses standardized airborne and impact sound insulation measures as the normal route for demonstrating the performance of separating floors between dwellings. That is a compliance question with defined methods and criteria. It is not a promise that every possible upstairs activity will be inaudible.
What the 2026 review found
A peer-reviewed systematic review published in Building and Environment examined 21 empirical studies of child-related noise in apartments, covering research from 2000 to 2025. It found that research has concentrated on structure-borne impacts such as running and jumping, while airborne sounds such as voices and toys have received less attention.
The authors concluded that standard impact sources have limited ability to reproduce real child-related noise. Laboratory stimuli are controllable and repeatable, but can simplify the timing, variation and context of everyday activity. Field measurements are more realistic, yet background sound and the unpredictability of events make them harder to isolate.
Different impacts excite a floor differently
A tapping machine is useful for standardized assessment, but its small, regular impacts are not mechanically identical to a child running or jumping. A heavier impact can put more energy into the low-frequency response of a floor, while a sequence of footsteps creates a changing pattern rather than a fixed laboratory rhythm.
One study included in the review compared standard sources with real activities in 30 concrete apartments. The correlation between single-number test results and real-event levels was generally low; a rubber-ball impact was spectrally closer to children's footsteps than the other standard sources examined. That is a finding from a particular building stock, not a universal replacement test.
Compliance and lived experience answer different questions
A compliant separating floor has met the applicable test requirement under the conditions of that test. A resident's complaint may concern a different source, a particular time of day, repeated events or a frequency range that is not well represented by the headline rating. Both pieces of evidence can be valid without being equivalent.
This is why it is unhelpful to use a passed test as proof that a reported event cannot be intrusive. It is equally unhelpful to treat a disturbing event as proof that the statutory test must have failed. The source, construction and transmission path still need to be identified.
The floor is a system
The received sound depends on more than slab thickness. Floor finishes, resilient layers, raised-floor supports, ceilings, junctions, workmanship and flanking paths all affect the result. Room size, furnishings and background level influence what is heard after the vibration reaches the receiving room.
A separate 2026 laboratory study of dry double-floor systems found that support-leg details influenced heavy-weight impact-sound performance and that some configurations could worsen low-frequency response. Its construction is common in Japan and should not be transferred directly to a British flat, but it reinforces a wider point: adding layers or supports does not guarantee improvement unless the complete system is understood.
A fair investigation needs more than one number
Child-related sound is also a social issue. Normal family activity, a neighbour's need for rest and the limitations of the building can all be present at once. An acoustic assessment should clarify the physical evidence without turning children into a defect or assuming that every dispute can be solved by insulation alone.
- Describe the actual events—walking, running, jumping, dropped objects, voices or furniture movement.
- Record timing, duration and repetition rather than relying only on a general impression.
- Use standardized tests for the question they are designed to answer.
- Where necessary, supplement them with representative event measurements and frequency analysis.
- Inspect floor finishes, ceilings, junctions and plausible flanking routes.
- Separate evidence about the building from assumptions about the people living in it.