MAX9814: DIY Hearing Aids & Bone Tech

How to Make a Hearing Aid? 

Here are two options.

Option 1: TDA2320A is said to have good performance and is super energy-efficient. 

Option 2: MAX9814 electret microphone version, simple to make, just connect the wires, with powerful AGC, able to suppress sudden loud sounds effectively.

For those interested in exploring bone conduction options, consider obtaining a PAM8406 amplifier board, a TP4056 charging board with a TYPE-C interface, and compatible headphones for modification into bone conduction devices. Repurpose iPhone linear vibration motors to serve as speakers, delivering sound when tapped on a surface. To enhance the bone conduction headphones, acquire linear vibration motors from iPhone 7 Plus and repurpose Sennheiser headphones for an extended usage period.

Connecting the MAX9814 to a wire yields unexpectedly positive results. Remember to attach a coupling capacitor to the amplifier board's output before connecting headphones or the next stage amplifier to ensure optimal functionality. The capacitance need not be excessive; around 10 microfarads suffices if low frequencies are not a priority. The MAX9814, drawing less than 4mA of current, proves highly sensitive, capturing even faint sounds from a considerable distance. Despite a presence of some background noise during quiet moments, it remains within acceptable limits.

Understanding the A/R terminal's purpose is crucial. This terminal facilitates the selection of AGC start and release times. Leaving this pin floating yields favorable results, significantly enhancing performance. To further refine the experience, grounding this pin offers superior noise reduction. Opting for the MAX9814 over the TDA2320A proves advantageous, offering excellent results with a minimal current draw, allowing a 1000mAh battery to sustain operation for an impressive 10-day period.

Moving forward, modifying the iPhone's linear vibration motor by incorporating an amplifier block yields promising outcomes. Should bone conduction effects be suboptimal, consider utilizing a hearing aid for enhanced perception. If conventional headphones suffice, removing the bone conduction amplifier extends the battery life substantially.

For user convenience, integrating a mercury switch is imperative. When positioned upright, the device is powered on; when facing down, it powers off. Installing the mercury switch requires precision to ensure reliable operation. The switch distinguishes between the front and back, enhancing user experience and overall functionality.

Explore the step-by-step process for bone conduction, hearing aid enhancement, and MAX9814 integration through the provided images:

1. Disassembled headphone coil

2. Linear motor

3. Application of bone conduction unit

4. Completed bone conduction headphones

5. Overall assembly

6. Final product