Note that the SR2 figure describes noise reduction achieved by the enclosure, not an absolute sound level. It cannot be compared with an absolute dB(A) reading from another supplier. Ask for the absolute figure at a stated distance and load point.

What Determines Compliance on Site

The enclosure is only part of the outcome. Four site factors change the measured result.

Distance to the receptor

The limit usually applies at a property boundary or a residential facade rather than at the machine. Moving the set further from the receptor is often cheaper than upgrading the enclosure.

Reflective surfaces

Hard walls and paved yards reflect sound and can raise the level at the receptor above the free-field prediction used in the quotation.

Exhaust and ventilation routing

Exhaust noise and cooling air noise are separate paths. A well-attenuated enclosure with an under-specified exhaust silencer will still fail a boundary test.

Operating hours

Many noise limits are stricter at night. A set that complies during the day may not comply at 02:00, which changes the specification from a quieter enclosure to a different operating strategy.

Removing the Noise Rather Than Attenuating It

Where the constraint is night-time or weekend operation, the more effective answer is often to stop the engine rather than to quieten it.

Pairing a battery system with the generator set allows the engine to run during permitted hours at an efficient load point while charging the battery, then shut down. The battery covers the restricted period silently.

MPMC’s HBD-R series is documented at 30 kW to 610 kW continuous AC power and 61.44 kWh to 610.6 kWh capacity, with LFP cells rated at 6,000 cycles at 90% depth of discharge and compatibility listed with DSE, ComAp, DEIF, Woodward, Smartgen and CAT EMCP controllers.

MPMC HBD Series containerised energy storage system.

A documented UK construction case listed by MPMC involved a noise restriction prohibiting generator operation between 17:00 and 07:00 and on Sundays. Six HBD-30-60 units at 30 kW and 60 kWh each were deployed to cover those periods.

A second UK case listed by MPMC involved a 56 kW diesel generator serving a 3 to 6 kW office base load. After a 30 kW / 60 kWh HBD-R unit was added, the refuelling interval moved from every two days to every seven days and the maintenance interval from every ten days to every sixty days.

Those outcomes belong to those sites and load profiles. Whether the same approach suits a different project depends on the restricted hours, the base load during those hours and the available recharge window.

Sizing the Silent Period

Where a hybrid arrangement is considered, four figures decide the configuration.