Capacitive Electret Microphone 58 dB 9 × 7 mm 🎙️

This compact electret condenser microphone capsule delivers reliable audio capture in a small 9 × 7 mm package. With 58 dB sensitivity and an omnidirectional pickup pattern, it’s ideal for voice and general-purpose sound acquisition in embedded systems, Arduino and Raspberry Pi projects, and a wide range of electronics components and modules. The internal FET buffer simplifies interfacing with preamplifiers and microcontroller ADC inputs.

Overview 🔎

Electret microphones are a type of condenser microphone that use a permanently charged electret material. This eliminates the need for an external polarizing supply, enabling low-power operation and a very compact form factor. The built-in JFET stage provides a high-impedance buffer for easier signal extraction.

Key Specifications 📐

• Form Factor: 9 × 7 mm (diameter × height) can
• Sensitivity: 58 dB (typical; commonly specified as −58 dBV/Pa at 1 kHz, 1 Pa)
• Frequency Response: typically 20 Hz to 20 kHz for wideband audio capture
• Directivity: omnidirectional (uniform pickup from all directions)
• Output Impedance: high; managed via the internal FET source follower
• Terminals: 2-pin capsule; case is ground (−), positive lead often marked with “+” or a notch

Applications 🚀

• Consumer electronics: smartphones, tablets, laptops, remote controls, and portable recorders
• Medical devices: hearing aids and compact diagnostic equipment
• Voice-controlled systems: smart assistants, smart home devices, and IoT nodes
• Professional and hobby audio: field recorders, lavalier builds, DIY microphones, and audio modules
• Embedded projects: Arduino and microcontroller voice input, robotics, and acoustic sensing

Advantages ✅

• Compact size: fits tight enclosures and portable designs
• High sensitivity: effective capture of low-level sounds
• Low power consumption: no external polarization required
• Cost-effective: excellent value versus other condenser mic types

Working Principle ⚙️

Sound waves vibrate a diaphragm that forms a variable capacitor with a backplate. The electret’s permanent charge establishes the electric field; diaphragm motion changes the capacitance and produces a corresponding voltage variation. The capsule’s internal FET buffers this high-impedance signal for external amplification and processing.

Integration & Usage Tips 🛠️

• Biasing (voltage and resistor): Provide a bias voltage to the mic via a series resistor to power the internal FET (for example, a few volts DC through 2.2 kΩ–10 kΩ). AC-couple the output with a capacitor (e.g., 1 µF–10 µF) into your preamp or ADC.
• Microcontroller interfacing: For Arduino or other microcontroller ADCs, create a mid-supply virtual reference and add an anti-aliasing RC filter. The Raspberry Pi lacks an analog input—use an external ADC or a USB audio interface.
• Preamp design: Use a low-noise op-amp or dedicated mic preamp with appropriate gain (e.g., 20–60 dB), high input impedance, and proper power rail filtering.
• Acoustic design: Place the port close to the sound source; use an acoustic grill or foam windscreen to reduce wind/pop noise. Enclosure porting and isolation greatly affect response.
• Noise/EMI: Keep leads short, add decoupling, and shield as needed. Star-ground sensitive analog sections.
• Polarity & handling: Connect the case to ground (−). Avoid mechanical shock and ESD to protect the diaphragm and FET.
• Note: This is an analog capsule (not I2S/PDM). Pair with suitable electronics components or breakout modules for best results.

Conclusion 🔚

The 58 dB capacitive electret microphone in a 9 × 7 mm package offers wideband response, omnidirectional capture, and easy integration with Arduino, Raspberry Pi (via ADC), and other microcontroller-based systems. Its small size, sensitivity, and low power needs make it a versatile choice for consumer, medical, IoT, and audio applications.