Whether it’s the low-frequency hum of rooftop chillers or the high-pitched rush of air through ductwork, noise from HVAC systems can cause serious disruptions in commercial buildings. In South Africa, where the demand for efficient, climate-resilient buildings continues to grow, so too does the importance of managing acoustic comfort.
At Attenu-tec, we specialise in helping commercial property professionals tackle HVAC sound issues head-on. Here are five of the most common HVAC-related noise problems found in South African commercial environments—along with tips on how to solve them.
1. HVAC Sound Problems – Fan Noise in Open-Plan Offices
With the shift towards collaborative, open-plan offices across Johannesburg, Cape Town, and Durban, building occupants are more exposed than ever to environmental noise. A common culprit? The mechanical noise from supply and return air fans—especially if they’re oversized, poorly maintained, or not properly isolated from ductwork.
What it sounds like: A low-frequency drone or hum that’s continuous and distracting, particularly in quiet spaces like meeting rooms or shared work areas.
The solution:
- Use variable speed drives (VSDs) to reduce fan speed during off-peak hours.
- Install correctly sized sound attenuators near the fan discharge and return grilles.
- Consider vibration isolators to reduce mechanical noise transmitted through structural components.
2. HVAC Sound Problems – Airflow Noise in Shopping Centres
In large shopping centres or retail developments like those in Sandton or Umhlanga, HVAC systems often operate at high airflow rates to maintain comfort across expansive, open areas. However, if air is forced through undersized ductwork or restrictive grilles, it leads to turbulence and regenerated noise.
What it sounds like: A high-pitched whooshing or hissing sound near diffusers and vents, often described as “white noise gone wrong.”
The solution:
- Ensure ductwork is properly sized and includes smooth transitions to reduce velocity.
- Install aerodynamically designed attenuators that minimise pressure drop while still delivering sound attenuation.
- Use perforated diffusers to break up air movement more gently.
3. HVAC Sound Problems – Equipment Vibration in Hospitals
In healthcare facilities like those in Pretoria or Bloemfontein, even low-level HVAC noise can negatively impact recovery, sleep, and communication. Noise from air-handling units, compressors, or pumps—especially when mounted on structural slabs—can transmit through floors and walls.
What it sounds like: A deep rumble or pulsing noise that may seem to come from “nowhere” but travels through the building structure.
The solution:
- Mount equipment on anti-vibration mounts or inertia bases.
- Use flexible duct connectors to decouple the duct from vibrating machinery.
- Include silencers specifically designed for low-frequency attenuation.
4. HVAC Sound Problems – Cross-Talk Between Rooms in Office Parks and Hotels
In buildings where multiple rooms share ceiling voids or ductwork—such as hotels, call centres, and multi-tenant office blocks—sound can travel from one space to another via return air paths. This is commonly referred to as cross-talk.
What it sounds like: Conversations, typing, or other activities in adjacent rooms being clearly audible through the HVAC system.
The solution:
- Install cross-talk attenuators or lined transfer ducts between spaces.
- Add internal acoustic lining in the return air paths to absorb and dampen sound transmission.
- Ensure duct runs are properly sealed and insulated.
5. HVAC Sound Problems – Start-Up and Shutdown Noise in Conference Centres
In larger buildings like civic halls or conference centres, HVAC systems may be programmed to operate intermittently or on schedules. When units start or stop, the sudden change in pressure and flow can create booming, banging, or rattling sounds that catch occupants off guard.
What it sounds like: Loud thuds, metallic bangs, or air pressure surges when systems switch on or off.
The solution:
- Use slow-start controls on fans and compressors.
- Incorporate dissipative attenuators to absorb noise spikes.
- Inspect ductwork for loose panels or fittings that may be amplifying the impact noise.
Why It Matters HVAC noise can negatively affect productivity, concentration, health, and the overall experience of a space. In sectors like retail, hospitality, healthcare, and education, noise complaints often lead to occupant dissatisfaction, operational delays, or costly retrofits. It’s far more effective—and economical—to address acoustic issues at the design or installation stage.
