If you are choosing a compressor for a shared workspace, ask how its noise figure was obtained before using the number to rank two models. The TRIMIX CS3 listing shows a noise figure of 76 dB and the TRIMIX CS4 listing shows 72 dB. Neither public listing states the measurement position, whether the figures were taken under comparable operating conditions, or whether they are the same quantity. Use the published numbers to frame a question for the supplier.
Ask the seller to identify the measurement
UK Health and Safety Executive guidance for machinery suppliers distinguishes emission sound pressure from sound power. It also explains the value of reporting measurement uncertainty, the test method and the operating conditions. Ask what the compressor figure measures, what frequency weighting was used and where the microphone was placed. For sound pressure, record the measurement distance and position. Ask whether the unit was running under load and whether the specification is an average, peak or another measure. A test report for the specific version is more useful to a buyer than an unqualified adjective such as quiet.
Separate product comparison from the proposed room
A comparable pair of test reports can help with selection. Actual exposure will still depend on the installation, where people work and how long they remain nearby. The U.S. National Institute for Occupational Safety and Health distinguishes a sound level at one point from an individual’s exposure over time. For example, a catalogue result for a machine operating alone does not tell you what a worker hears beside other running equipment. Consider the proposed work area separately with the people responsible for its assessment, and ask the supplier for the documented installation requirements.
Put the same question in both quotes
Use the CS4 inquiry to request the published measurement basis and ask whether like-for-like CS3 documentation is available. Keep the comparison provisional if the two answers describe different quantities or test conditions. Use the exact model documentation for installation and operating restrictions. The inquiry prepares an email for you to review and send.
Evergreen buyer guide checked November 14, 2026. The listings and cited HSE page are undated. NIOSH’s page was published May 15, 2024 and updated October 28, 2026.
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