English 
Chinese This guide is based on Espressif’s ESP32-S3 voice development board, providing best practices for integrating MEMS microphones into voice-controlled devices. The ESP32-S3 is a powerful dual-core SoC with built-in Wi-Fi, Bluetooth, voice processing capabilities, and support for low-power operation—making it ideal for smart audio, IoT, and TWS devices.
🔗 Explore compatible MEMS microphones from SISTC:
👉 https://sistc.com/product-category/mems-microphone/
MEMS Microphone Electrical Performance Requirements
- Type: Omnidirectional MEMS microphone
- Package: SMD-4P, 2.8 × 1.9 mm
- View:
Sensitivity
- Analog mic: ≥ –38 dBV @ 1 Pa
- Digital mic: ≥ –26 dBFS
- Tolerance: ±2 dB (±1 dB recommended for mic arrays)
Signal-to-Noise Ratio (SNR)
- Minimum: 62 dB
- Recommended: >64 dB
- Frequency response within ±3 dB over 50 Hz – 16 kHz
- PSRR: >55 dB
Microphone Structural Design Guidelines
| Parameter | Recommendation |
|---|---|
| Mic port diameter | > 1 mm |
| Acoustic cavity volume | As small as possible |
| Port length-to-diameter | < 2:1 |
| Housing thickness | ~1 mm (increase opening area if thicker) |
| Mic sealing | Use silicone rings or foam for vibration isolation and sealing |
| Dust protection | Add mesh over mic hole |
| Bottom-port mic mounting | Add structural stand-off to avoid full contact with flat surfaces |
| Placement | Avoid proximity to speakers or vibration sources |
Mic Array Design Recommendations
2-Mic Array
- Spacing: 4–6.5 cm
- Mic-to-mic axis: Parallel to horizontal axis
- Place as close to horizontal center of product as possible
3-Mic Array
- Shape: Equilateral triangle (120° angle)
- Equal spacing: 4–6.5 cm
Array Component Guidelines
- Use identical model and vendor for all mics
- Sensitivity variation: <3 dB
- Phase difference: <10°
- Use identical acoustic housing for consistent response
Mic Sealing Validation Test (Using Putty)
To verify acoustic sealing performance:
- Play white noise at 90 dB SPL from 0.5 m above the mic
- Record audio (file A) for ≥10 seconds
- Seal mic port with putty, record again (file B)
- Compare spectrum: target attenuation ≥25 dB between 100 Hz – 8 kHz
- ≥30 dB recommended for optimal sealing
Echo Reference Signal Design
- Tap echo signal close to speaker driver (DA-PA stage)
- Speaker output THD should meet:
- ≤10% @ 100 Hz
- ≤6% @ 200 Hz
- ≤3% @ 350 Hz+
- Max SPL at mic position: ≤102 dB @ 1 kHz
- Echo signal should not clip ADC input voltage
- Use low-pass filter (>22 kHz cutoff) if tapping from Class-D amplifier
- Capture echo at peak –3 to –5 dB level
Microphone Consistency Verification
To ensure mic uniformity across the array:
- Play white noise at 90 dB SPL from 0.5 m above the device
- Record ≥10 seconds from all mics
- Ensure amplitude difference <3 dB
- Check sampling consistency across channels
About ESP32-S3: Ideal for Smart Voice Devices
The ESP32-S3 from Espressif is a low-power dual-core MCU with robust AI voice support, perfect for:
- Smart home controllers
- Wearable audio devices
- USB voice peripherals
- On-device wake word and speech recognition
- Battery-powered IoT nodes
Highlights
- Wi-Fi + Bluetooth LE 5
- 2 × Xtensa LX7 cores @ 240 MHz
- 384 KB ROM, 512 KB SRAM, external flash support
- 2 × I²S interfaces for audio input/output
- ULP co-processor for low-power operation
- Multiple analog and digital GPIOs for mic integration
📘 Full ESP32-S3 specs: Espressif Official Datasheet
Conclusion
Designing a robust voice interface with the ESP32-S3 requires careful consideration of MEMS microphone characteristics, structural acoustics, array layout, and echo signal handling. Following these design principles helps maximize speech recognition accuracy, reduce noise pickup, and improve user experience in smart audio applications.
📢 Need help selecting a MEMS mic for your ESP32-S3 project?
👉 Contact SISTC
🔎 Explore our full product line:
👉 https://sistc.com/product-category/mems-microphone/
