{
 "id": "hp_mcs020a_method",
 "name": "The MCS 020 a) sound calculation",
 "category": "heat_pump_noise",
 "value_num": null,
 "display": "Lp = Lw + 10 log(Q ÷ (4 × π × r²)) − AB",
 "unit": "formula, sound pressure level in dB(A) at one assessment position",
 "period_start": "2025-04-14",
 "period_end": null,
 "period_kind": "page_date",
 "deadline": null,
 "source_url": "https://mcscertified.com/wp-content/uploads/2025/04/MCS-020-a-Issue-1.1-Final.pdf",
 "source_org": "MCS, MCS 020 a) Issue 1.1",
 "checked_at": "2026-09-30",
 "recheck_by": "2026-12-29",
 "history": [],
 "public_note": "The sum takes the heat pump's A-weighted sound power level from the maker's data (never the low noise mode figure, and never a sound pressure figure), adds a correction for how many hard surfaces sit within 1 metre of it, takes off the spreading over distance, and takes off a correction for a solid barrier in the way. Distance is measured to the nearest 0.1 metre from the middle of the unit. More than three reflecting surfaces, as in a small lightwell, does not meet the standard at all.",
 "next": null,
 "url": "https://hearthsum.co.uk/api/hp_mcs020a_method.json"
}