Techinfo
Technical Information
Ways to Control Vibration, Shock, and Audible Noise
Overview of Mitigation Techniques
1.Vibration control
To convert vibration energy into thermal energy and dampen vibration
2.Vibration Damping (Vibration Isolation)
To damp and insulate vibrations transmitted from the vibration source to the target object
3.Sound Absorption
To absorb sound propagating through the air
Point of Vibration Damping (Vibration Isolation)
１．Reducing vibration transmissio
To achieve vibration isolation, ensure the vibration transmission coefficient (τ) is less than 1.
Therefore, the frequency ratio (f/f0) should be greater than √2, preferably ≥ 2.
When a vibration source is supported with vibration damping material, the excitation force of the vibration source is denoted as F0, and the transmitted force to the non-vibrating source is denoted as F.
Then the vibration transmission coefficient (τ) can be expressed as the following equation.
| Frequency Ratio f/f0 | Vibration transmissibility τ | Vibration State | Damping/isolation effectiveness |
|---|---|---|---|
| f/f0=0 | 1 | F0=F | Not effective |
| f/f0=1 | ∞ | F0<F | Resonated |
| f/f0=√2 | 1 | F0=F | Not effective |
| f/f0>√2 | ＜1 | F0>F | Effective |
２．Expanding area of vibration isolation effectiveness
Expanded Vibration Isolation Region
By shifting the resonance frequency f0 to a lower frequency, area of vibration isolation effectiveness can be expanded.
Additionally, the vibration isolation effectiveness will also improve with better damping characteristics.
<Method to shift the resonance frequency lower>
Reduce the spring constant (make the hardness of the vibration isolation material softer or decrease the rigidity).
Increase the mass (load) on the vibration isolation material.
３．Reducing resonance magnification
The resonance magnification can be reduced by using a high-damping material.
The damping magnitude of the vibration isolation material is expressed by the loss factor (tan δ).
Accounting for damping, the vibration transmissibility τ is defined by the following equation.
As the loss factor increases, the resonance magnification is suppressed, but it is important to note that the vibration transmissibility in the vibration isolation area deteriorates.
Therefore, selecting a vibration isolation material with a suitable loss factor for the specific application is critical.
What is Vibration Control?
Technique to convert vibration energy into thermal energy and dampen vibration.
It is necessary to clearly distinguish between ""Vibration Damping"" (Vibration Isolation) and ""Vibration Control".
Vibration damping (vibration isolation) is a fundamental method for reducing vibrations by using damping material to block the transmission of vibration energy.
However, in practical applications, this may not always be feasible.
In such cases, vibration control"" technique is applied to reduce the transmitted vibration.
When vibrations cause the surface of an object to repeatedly bend, the damping material undergoes stretching and shearing deformations.
Due to internal friction within the material, the vibration energy is converted into heat energy, resulting in vibration damping.
The loss factor represents the damping capability of vibration control material, with higher values being preferable.
However, this performance is highly dependent on temperature, so it is important to choose a vibration control material suitable for the operating temperature of each application.
What is buffering material?
Generally, impact refers to a large acceleration that occurs over a short period.
The most common causes of impacts in portable electronic devices are drops onto the floor and collisions with hard surfaces.
Buffering means to soften an impact.
Buffering materials cushion and reduce strong impact forces with a specified stroke.
When an object is simply dropped, a powerful impact force is generated upon colliding with the hard surface.
However, by placing an impact-buffering material (such as gel) between the dropped object and the hard surface, the absolute impact force can be minimized.
