This kit design for only those person who is physically dumb and deaf. Many Deaf people do not use a spoken language, thus they are technically “mute”.
The heart of this circuit is a MIC. The MIC detects the noise intensity and generates an analog voltage. This analog variation is converted into digital form using a dual op-amp IC LM358. The op-amp is used as a comparator in the inverting mode to do so. In this operation, we set a reference voltage with the preset 10k (potentiometer) which connected to pin 2 of IC, and by using preset 10k we can adjust. The output from the LM358 i.e. from pin no 1 drives vibration motor.