Vibration Isolation Calculator – Natural Frequency & Load Class Online
Work out natural frequency, static deflection, isolation efficiency and bearing pressure in seconds – including a recommendation for the right load class.
1. Excitation frequency of your machine
2. Required vibration isolation
Result (guide values)
Simplified, undamped single-mass model. The calculated isolation efficiency describes vibration transmission – it does not mean an equivalent reduction in noise level.
3. Bearing pressure & possible load classes
The classes are candidates for preselection. A material recommendation requires the characteristic curves of the specific product type – we check these for your quote.
New: Vibration Isolation Check. Check your planned mounting in two minutes for overload, resonance across the whole speed range, acoustic bridges and missing information – with a traffic-light result and optional frequency measurement using your smartphone. Open the Isolation Check →
How the calculation works
A resilient mounting only isolates vibration when its natural frequency is well below the excitation frequency of the machine. The isolation effect only begins at a frequency ratio of more than √2 (≈ 1.41) – the larger the ratio, the better. If the two frequencies are close together, there is a risk of resonance and the vibration is amplified.
The calculator uses the simplified model of an undamped single-degree-of-freedom system: isolation efficiency = 1 − 1 / ((f / f0)² − 1) and f0 ≈ 15.76 / √(static deflection in mm). The results are guide values. Damping, the dynamic stiffness of elastomers, rocking modes and the substrate are not taken into account – which is why we design every solution individually.
Typical excitation frequencies – open directly in the calculator
| Machine / plant | Typical excitation frequency | In the calculator |
|---|---|---|
| Transformer on a 50 Hz network | 100 Hz (harmonics 200 / 300 Hz) | Check 100 Hz |
| Transformer on a 60 Hz network | 120 Hz | Check 120 Hz |
| Electric motor / pump, 4-pole | approx. 1,450–1,500 rpm ≈ 24–25 Hz | Check 1,450 rpm |
| Electric motor / pump, 2-pole | approx. 2,900–3,000 rpm ≈ 48–50 Hz | Check 2,950 rpm |
| Standby generator set | 1,500 rpm = 25 Hz | Check 1,500 rpm |
Calculator FAQ
How do I convert the speed into the excitation frequency?
Divide the speed by 60: 1,500 rpm corresponds to 25 Hz, 2,950 rpm to around 49 Hz. With reciprocating machines and multi-cylinder engines, multiples of the rotational frequency can also occur – the lowest relevant excitation frequency is generally what governs the design.
Why does the frequency ratio have to be above √2?
Below η = √2 ≈ 1.41, the resilient mounting transmits more vibration than would arrive without a mounting – resonance occurs around η ≈ 1. A noticeable isolation effect only begins well above that; in practice, a ratio of 2.5 to 3 or more is the aim.
What isolation efficiency makes sense for my application?
For industrial halls, 70–80 % is often sufficient. In buildings with offices, homes or sensitive equipment, 85–95 % is usually the aim. What matters is how much the vibration at the receiver needs to be reduced – we will be happy to clarify this as part of the design.
How many dB does an isolation efficiency of 90 % correspond to?
An isolation efficiency of 90 % means a transmissibility of 0.1 – that corresponds to about 20 dB less vibration transmission. 80 % corresponds to around 14 dB, 95 % to around 26 dB and 99 % to around 40 dB. This describes structure-borne noise, not directly the audible sound level in the room.
Which frequency do I use if there are several sources of excitation?
Use the lowest relevant excitation frequency – it is the most critical for isolation. With pumps and fans, blade-pass or rotational tone frequencies can also occur, and with transformers, harmonics at 200 and 300 Hz; these are higher and are then usually isolated even better.
What happens during run-up when the machine passes through resonance?
When starting and stopping, the machine briefly passes through the natural frequency of the mounting. With a quick run-up, this is usually not critical. With frequent starts, long run-down or speed control via a frequency inverter, the entire speed range should be checked – higher damping or different tuning may then make sense.
Why does the dynamic stiffness differ from the static stiffness?
Elastomers are stiffer under rapid, alternating loading than under static load. The actual natural frequency is therefore usually slightly higher than the value derived from the static deflection. We take this into account in the design using the characteristic curves of the specific product type.
What if the centre of gravity is off-centre?
Then the support points are loaded unequally. So that the machine deflects evenly and no rocking modes occur, the bearing area at each support point is adapted to its load – for example with different pad sizes or load classes.
Want a binding design?
Send us the weight, footprint and speed of your machine – we will select the right material, hardness and thickness.
You will find all load classes and materials under Materials & technical data.
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