The first step to take in this project is to build and test the circuitry to make sure the concept will actually work as intended. I developed this schematic over the course of a few days. The parts list and pricing are all from SparkFun.

Directional Hearing Aid Schematic

Directional Hearing Aid Schematic

The LM358 should amplify the sound enough to allow for the vibration motors to spin when a sound is heard. Given the analog nature of the circuit, the vibration of the motor should be directly proportional to the sound being picked up by the microphone. The total cost of the project, for setup will be about 40 USD (probably closer to 45 USD after shipping), which will include capacitors and resistors for 2 or 3 of these items, and a breadboard for testing. It is a personal pet peeve when people write parts lists assuming you have boatloads of capacitors, resistors, and breadboards laying around. This price list includes everything you need, minus the battery.

Component Part # Price per Unit Quantity Total
Microphone COM-08635 0.95 2 1.9
Vibration Motor ROB-08449 4.95 2 9.9
LM358 Op-Amp COM-09456 0.95 1 0.95
Breadboard PRT-00112 9.95 1 9.95
2 Pin Connectors PRT-10501 0.5 4 2
9V Battery Clip PRT-10512 2.95 1 2.95
Barrel Adapter PRT-10811 0.95 1 0.95
1k Ohm Resistor COM-13760 0.95 1 0.95
10K Ohm Resistor COM-11508 0.95 1 0.95
Capacitor Kit KIT-13698 6.95 1 6.95
TOTAL COST 37.45