Explore the design considerations for silicon microphones, including sound input hole design, acoustic chamber considerations, and techniques to prevent feedback and resonance.
1. Sound Input Hole Design (Silicone Sleeve and PCB)
Silicone Sleeve Sound Input Hole Design: The diameter of the silicone sleeve sound input hole should be greater than 0.8mm to avoid blocking the sound input hole of the silicon microphone.
PCB Sound Input Hole Design: The hole diameter on the PCB should be between the external diameter of the microphone sound input hole and the internal diameter of the sealing ring to ensure proper sound input flow.
2. Acoustic Chamber Design
One key acoustic structure that influences sound quality is the Helmholtz resonator, which has dimensions smaller than the sound wavelength. It consists of a wider internal cavity and a narrow opening to the outside. For example, when a wide gasket is used between the silicon microphone PCB and the device housing, it may form a Helmholtz resonator.
This structure may lead to a peak in high-frequency response. Unless the design intentionally targets this peak, it should be avoided. To prevent such resonance, the gasket should be as small as possible, or the PCB should be placed directly against the device housing.
To prevent feedback, the silicon microphone should be tightly connected to the housing. Using rubber or gaskets helps mitigate feedback issues.
If the housing includes wall structures for securing the silicon microphone, rubber should be used to ensure reliable connection.
When industrial design constraints require longer acoustic paths, the effective path diameter should be close to or smaller than the opening of the device housing. Multiple smaller holes in the device housing may be used instead of a single exit point.
Due to material flexibility, cavity leaks, and other factors, the calculated resonant frequency may differ from the actual measured result.
