EN
AR
CS
DA
NL
FI
FR
DE
EL
IT
JA
KO
NO
PL
PT
RO
RU
ES
SV
TL
IW
ID
LV
SR
SK
VI
HU
MT
TH
TR
FA
MS
GA
CY
IS
KA
UR
LA
TA
MY
The Label 'Silenced' Is Not a Specification
Every manufacturer selling a box-type breaker calls it silenced. The word has become a product category name rather than a performance claim. The problem is that two breakers, both sold as silenced, can produce 108 dB(A) and 118 dB(A) respectively — a ten-decibel difference that means the first produces roughly one-tenth the sound energy of the second. On a hospital-proximity project with a permit ceiling of 70 dB at the boundary, those two units produce completely different compliance outcomes. Selecting by category rather than by measured figure is the most common and most expensive mistake in noise-sensitive project procurement.
The correct starting point is the documented sound power level measured under ISO 3744, expressed in dB(A). That is a standardised test method. It is what CE marking for noise emissions requires, and it is the figure a local authority enforcement officer will check against the site permit. A specification sheet that lists only 'sound-suppressed housing' or 'noise-reduced design' without a dB(A) figure is not giving you what you need. Ask for it directly, in writing, before procurement. If the supplier cannot provide it, treat the unit as uncertified for noise purposes.
The second misconception is that 'silenced' and 'quieter than open-type' mean the same thing at all power classes. At the small-carrier end — 1 to 5 tonnes — a box-type breaker may be only marginally louder than an equivalent open unit because the percussion mechanism is physically small and the housing provides meaningful isolation. At the 15–25 tonne class, the percussion energy is an order of magnitude higher, and the housing's acoustic isolation is a smaller fraction of total noise output. A box-type heavy breaker can still easily exceed 110 dB(A). Silence is a relative term. The dB(A) number is not.
Four Site Types — Noise Limit, Required Spec, and What to Watch
The table covers the four most common noise-sensitive site contexts. The 'watch-out' column addresses the error that is specific to each — not the general advice, but the thing that actually causes the compliance failure or the callback.
|
Site Type |
Noise Limit |
Required Spec |
Watch-Out |
|
Indoor renovation (occupied building) |
Often 75–80 dB at boundary; check building management rules — can be stricter than local code |
Box-type; compact carrier to fit lifts and corridors; high-frequency lower-energy blows to limit vibration into the structure |
Carrier size matters as much as noise level — a quiet breaker on an 8 t machine may be physically too large to enter the floor being demolished |
|
Hospital / school proximity (< 50 m) |
Typically 70 dB daytime; night work usually prohibited regardless of dB level |
CE/ISO 3744 certified noise rating required — 'silenced' label alone is not sufficient; ask for documented dB(A) figure |
Not all box-type units are tested to the same standard; request the measured sound power level, not the manufacturer's estimated figure |
|
Municipal road & utility trenching |
Local authority limit varies; 85 dB common daytime; traffic management may set tighter limits near live lanes |
Box-type preferred; flat or narrow chisel for trench work; check return-line back pressure — road work involves frequent repositioning that spikes oil temperature |
Frequent short breaking cycles raise oil temperature faster than sustained work; monitor fluid temperature and idle the carrier between positions |
|
Night-shift construction |
70–75 dB at site boundary is typical for permitted night work; confirm with permit — some jurisdictions allow only specific equipment categories |
Only a certified silenced breaker meets night limits; open-type units cannot be made compliant by running at lower throttle |
Impact mechanism generates the noise, not the carrier engine — reduced engine speed does not reduce breaker dB level |
What the Housing Actually Does — and What It Cannot
The box enclosure does three things. It contains airborne noise — sound waves that would otherwise radiate directly from the percussion mechanism into open air. It absorbs structure-borne vibration at the mounting interface between the power cell and the outer casing, using rubber or polyurethane damping blocks. And it keeps the power cell physically protected from falling debris, which matters in indoor demolition where material falls back onto the breaker. What it cannot do is eliminate the vibration that travels through the tool and chisel into the material being broken, and from there into the adjacent structure. That vibration path exists regardless of how good the enclosure is. For indoor work near occupied spaces, the tool's contact with the floor or wall is the dominant vibration transmission route, not the noise from the casing.
This is why breaker selection for indoor work needs to consider impact energy, not just noise level. High impact energy on a thick reinforced slab transmits less vibration into adjacent structure than repeated low-energy blows, because each high-energy strike propagates the fracture more efficiently and reduces total strike count. The opposite intuition — that a lighter, quieter breaker is always safer indoors — is wrong when the work involves heavy concrete. The right tool completes the work in fewer impacts. Fewer impacts means less cumulative vibration transmitted into the building.
The damping blocks inside the housing wear over time, exactly like the external shock absorber sleeves discussed elsewhere in this series. A worn damping block lets the power cell contact the outer casing directly, producing metal-on-metal rattle that adds 5–8 dB to the measured output and often triggers site noise complaints even on projects that were previously compliant. Inspect the damping blocks at 250-hour intervals for indoor and municipal work. A unit that passed the pre-project noise test will fail on-site if the blocks have degraded during the contract.
