Parking AC noise: compare the sound where the driver rests.

How the layout changes the noise path

These are evaluation points, not a measured ranking. A fleet should compare the finished installation in a representative cabin rather than assume that every rooftop unit shares one noise level.

Read the noise rating before comparing the number

Sound pressure describes sound at a measurement location and depends on distance and the acoustic surroundings. Sound power describes the source’s acoustic output. They are different quantities: do not rank a sound-power figure against a sound-pressure figure just because both use decibels.

Daikin’s explanation of air-conditioner noise ratings discusses this distinction and indoor versus outdoor noise. Its residential examples are background information, not VETHY vehicle test results.

Ask whether a stated value is A-weighted, where it was measured, which fan/compressor mode was used and whether the unit was installed in a vehicle. An outdoor reading several metres from a unit cannot be treated as sound at a driver’s pillow.

Build a repeatable sleeper-berth comparison

1. Fix the vehicle and location. Record cab variant, trim, bunk position, doors/windows, curtains and mounting arrangement. Mark the microphone position so it can be repeated.
2. Record background sound. Measure the surroundings with the A/C off. Traffic, wind and adjacent equipment can affect the reading.
3. Test the intended duty. Record ambient and cabin temperature, supply voltage, setpoint, fan mode and compressor operating state. Separate hot-cabin pull-down from steady rest operation.
4. Record comfort alongside sound. Keep the cabin temperature and electrical consumption in the trial record. A low setting that does not meet the cooling duty is not an equivalent comparison.
5. Separate inside and outside results. Use consistent measurement positions, equipment and procedure. Record tonal, rattling or intermittent sounds as observations, alongside the measured values.

Use suitable calibrated measurement equipment and an agreed method for purchasing acceptance. A phone recording can help identify a changing sound, but it does not establish a comparable laboratory noise rating. No VETHY sound-level figure is claimed in this guide.

Review installation and service causes

If sound changes after fitting or during use, inspect the installation and equipment condition through the approved service process. Check for loose trim, component contact, obstructed airflow, dirty filters or a damaged fan before assuming the compressor design is the cause.

Changes to mounts, seals or operating modes should follow the manufacturer’s instructions. Do not block air paths or add improvised material around moving components to suppress a noise. The installation handover checklist helps keep a reference record for later investigation.

For a model comparison, combine these checks with the single- and twin-rotary compressor guide. A component description cannot replace the finished vehicle’s acoustic result.

Put the comfort requirement into the RFQ

Specify the sleeper layout, target cooling duty, evaluation positions, modes and acceptance method. Ask suppliers which documented acoustic evidence is available for the proposed configuration, and agree how the sample installation will be evaluated before rollout.

Review VS02-PRO for a rooftop layout, or VX3000SP and EcoMax 3S for split layouts. These links provide configuration and specification details; they do not establish a verified “quietest” model ranking.

Send the vehicle information and evaluation brief through the technical RFQ checklist. For a custom cabin or ducted system, start with the HVAC integration requirements.