KEVOS® MAKEOS · Engineering
Machinery Noise: Machine Level, Combined Sources and Distance
How loud is this machine on its own, how loud are several sources together, and how does level fall with distance?
Noise level of a single machine from the total and background readings by the handbook method, the combined level of up to four sources, and the free-field change in level with distance from a source.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Calculation | choice | Choose the calculation. |
| Total level, machine running | dB | Meter reading with everything running. |
| Background level, machine off | dB | Meter reading with the machine in question switched off. |
| Source 1 | dB | Level of the first source. |
| Source 2 | dB | Level of the second source. |
| Source 3 (0 = none) | dB | Level of the third source. |
| Source 4 (0 = none) | dB | Level of the fourth source. |
| Level at the reference distance | dB | Level measured at the reference distance. |
| Reference distance | m | Distance of that measurement from the source. |
| New distance | m | Distance at which the level is wanted. |
Method and formulas
- Machine alone: M = 10 log₁₀(10^(T/10) − 10^(B/10)), as in the handbook (51 and 49 dB give 46.7 dB).
- Combined: L = 10 log₁₀ Σ 10^(Lᵢ/10).
- Distance (free field, point source): L₂ = L₁ − 20 log₁₀(r₂ ÷ r₁).
- Example: 51 dB total with 49 dB background puts the machine at 46.671 dB.
Limitations
- Levels must be on the same weighting (for example dBA).
- Distance law holds in a free field; reverberant shops fall off more slowly.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Measure one machine’s noise in a busy shop
- Predict the level when another machine is added
- Estimate the level at a work station further away
Who it is for
- Health and safety officers
- Maintenance engineers
- Plant engineers
What you get
- Machine, combined or distant level
- Difference from the reference
- Measurement validity
Interpreting the result
- When background is 10 dB or more below the total, the total reading is effectively the machine’s level.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3455–3456. Topic reference; no source tables or recommended settings are reproduced.
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Open the Machinery Noise: Machine Level, Combined Sources and Distance calculator
