DocID025705 Rev 1

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AN4427

Acoustic gasket and sealing guidelines

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Figure 9. Subdomain materials

The following table summarizes the acoustic properties of the most common materials used

by manufacturers of electronics: plastic or aluminum concerning the covers; soft and hard

rubber concerning the gasket; silicon and PCB concerning the electronic components.

The following graphic depicts the behavior of the magnitude of the resonance peak, keeping

silicon and MEMS membrane materials fixed and changing the material of the gasket only.

While the geometry of the entire application behaves as a resonator, the acoustic property

of the material works as a damping factor. The peak is attenuated in proportion to the

softness of the material used as the gasket. The gasket designer can choose the material of

the gasket according to his own needs. Where the frequency response must be kept flat as

much as possible, the materials involved must be chosen as supple as possible.

Table 4. Acoustic properties of materials

Material

Sound velocity in material (m/s)

Air

1.2

343

Aluminum

2700

6400

PCB

1850

2740

Glass

2400

4000

Silicon

2000

1500

Hard rubber

1520

150

Soft rubber

200

150

Plastic

1200

2500

Lead

11340

1150

Iron

7870

5000

MEMS membrane

120

150