HVAC Noise Criteria for Commercial Buildings

What You Need to Know

Noisy air conditioning drives tenants out. AS/NZS 2107:2016 (the Australian Standard for indoor noise levels) sets the target. For a private office, background noise from HVAC must stay between 35 and 40 dBA. For an open-plan office, the range is 40 to 45 dBA. Go above these limits and people complain. Go too far below and every conversation carries across the floor.

• Background noise in private offices must fall within 35–40 dBA (AS/NZS 2107:2016, Table 1)
• Open-plan offices allow 40–45 dBA (AS/NZS 2107:2016, Table 1)
• Conference rooms and boardrooms need 30–35 dBA for clear speech (AS/NZS 2107:2016, Table 1)
• In residential and aged-care buildings (Class 2/3/9c), walls between a plant room and a sole-occupancy unit need a minimum Rw of 50 (Class 2/3) or Rw 45 (Class 9c) (NCC 2025, F7D6)
• Ducts and pipes passing through walls next to habitable rooms need Rw + Ctr of at least 40 (NCC 2025, F7D7)
• Pumps must connect to pipes with flexible couplings to stop vibration transfer (NCC 2025, F7D8)
• For Class 5 commercial offices, NCC Part F7 does not prescribe specific noise limits - AS/NZS 2107 is the primary benchmark, enforced through Green Star, NABERS, and lease requirements
• Green Star IEQ credits require meeting the AS/NZS 2107 upper limits across all occupied spaces

Take a typical commercial floor with a rooftop plant room above the top-floor offices. The AHU (air handling unit) runs at roughly 85–95 dB(A) sound power level. You need to cut that down to 40 dBA or less at the nearest office. That is a 45–55 dB reduction, and it does not happen by accident.

Noise travels two ways: through the ductwork and through the structure. Duct-borne noise comes from the fan and from air turbulence at fittings. A duct attenuator (silencer) in the supply and return ducts can cut 10 to 30 dB, depending on length and type. Lining the first 3 to 5 metres of ductwork after the AHU with acoustic insulation adds another 10 to 20 dB of reduction.

Structure-borne noise comes from vibrating equipment. A chiller or pump bolted straight to a concrete slab sends vibration through the building like a tuning fork. Spring isolators under each piece of equipment, plus an inertia base for pumps and large fans, break that path. Flexible connections on all duct and pipe connections to the equipment stop vibration jumping across.

The other trap is breakout noise. Sound inside a duct can radiate through thin sheet metal walls into the ceiling void below. If a main supply duct runs above a boardroom (30–35 dBA target), the duct may need external lagging or a heavier gauge to keep breakout noise under control.