Miniature Non-Directional Microphone

Background:

Small microphones that can be manufactured with low cost are highly desirable components in many portable electronic products. In current design approaches, however, the small size of the microphone results in diminished sensitivity to sound, and in particular poor sensitivity to low frequencies. As a result, great care must be taken in the design to maximize sensitivity, which generally adds to the complexity and cost of the device.

 Technology Overview:

This technology consists of a microphone diaphragm having a mechanical sensitivity that does not diminish as the area of the diaphragm is reduced. The diaphragm is compliantly suspended over an enclosed air volume having a vent port, wherein an effective stiffness of the diaphragm with respect to displacement by acoustic vibrations is controlled principally by the enclosed air volume and the port. The microphone may be formed using silicon microfabrication techniques and has sensitivity to sound pressure substantially unrelated to the size of the diaphragm over a broad range of realistic sizes. The diaphragm is rotatively suspended for movement through an arc in response to acoustic vibrations, for example by beams or tabs, and has a surrounding perimeter slit separating the diaphragm from its support structure. The air volume behind the diaphragm provides a restoring spring force for the diaphragm.

 Advantages:

• Provides a tiny microphone diaphragm that is dramatically less stiff than what can be achieved with previous approaches
• Avoids imposing a large force between the diaphragm and the backplate due to a sensing voltage, and employs a different transduction approach, which does not require mechanical stiffness of the out-of-plane motion of the diaphragm to avoid collapse.

Intellectual Property Summary:

• U.S. 7,903,835
• U.S. 8,374,371