Given that vibration test has passed successfully, the next phase is adding an audio microphone. 

Automatic vibration of the bracelet, initiated by surrounding sound, has application both during daytime activities and while its owner sleeps. For example, if Kosta temporary do not use hearing aid while playing outside, the bracelet can warn him to the sound of a car horn, to the noise of roadworks or to the loud calling of his parents.

Vibhear bracelet should also warn Kosta about danger sounds during his sleep, when he is the most vulnerable. During the sleep, hearing aid is removed and the child is completely isolated from its environment. If by accident fire occurs and sound alarm is triggered, child will continue to sleep probably until the smoke wakes him up. Thus it is important that bracelet vibrates on certain sounds and woke up its owner.  

First test allowed us to find out how strong should vibration be to wake up Kosta and now we will test automatic vibration functionality triggered by predefined sound intensity e.g. fire sound alarm.

HW testing

We use Arduino Uno and an audio microphone for quick testing. The microphone plate has two output pins, one digital and one analogue. The digital output is connected to the Arduino pin and used for measuring the sound level. When the sound goes beyond the predefined threshold, Arduino Uno receives information through the intercept that the surrounding sound is strong enough, and the acquisition of the signal through the analogue input begins. Once the signal is recorded, it is necessary to perform signal filtering. For this purpose, we will probably use real-time digital signal processing (DSP) library for Arduino. This is only a temporary solution because the bracelet will not use Arduino but most suiting DSP or some Cortex micro-controller.