Why the room matters
Reflections from hard walls, distance and machine position affect what a worker hears. A-weighting adjusts the frequency sensitivity of the measurement. The same level need not mean the same sound character; tonal or impulsive components may matter for further assessment.
Noise reduction must not overheat the compressor
Placing the machine away from the workplace, isolating vibration transmission and suitable acoustic measures can help. Silencers and enclosures, however, affect ventilation and service access. An unusual new sound is also a reason for diagnostics, not simply for enclosing the machine.
What to check in practice
- Compare LpA with LpA under identical conditions, or LwA with LwA.
- For sound pressure, check the distance, machine operating mode and acoustic environment.
- If the sound changes, record when it occurs and have the machine's condition assessed.
Example scenario
Two independent sources each produce 70 dB(A) at the same point. Together they produce approximately 73 dB(A), not 140 dB(A). This is a logarithmic sum under the stated conditions, not a general prediction for another room.
What to watch out for
- Directly comparing sound pressure and sound power.
- Adding decibels arithmetically.
- Restricting the air supply in an attempt to eliminate noise.
Can noise be determined from motor power?
Not reliably. Design, speed, enclosure, fan, operating mode and installation all matter. Design requires documented acoustic data and, where appropriate, on-site measurements. A ventilation calculator does not replace acoustic design.