I want to make a simple system to detect baby crying. I have an electret microphone, 0.5 W and 8 ohm speaker and arduino uno. So how can I implement a system with these. I want the microphone to input the voice and use arduino to detect if it is baby's voice, if it is baby's voice, arduino will on speaker and output the voice through the speaker. It doesnt have to be very smooth voice coming out from speaker, bit of noise is acceptable. I need guidance on what I should do and the circuit needed to accomplish this.
I am thinking of a VU meter ( measure dB ). A VU meter is to measure how lound a sound is. So when a baby is crying, It is lound, when he/she sleeping, it is very calm. You need the SparkFun Electret Microphone Breakout - BOB-12758 - SparkFun Electronics , use the analog input, program the Arduino as a VU meter and when a level is high, activated an amplify tone and "reset" it after everything is calm again. That breakout board is just a mic and op-amp set at 20 gain.
For the arduinopi idea, the device is a mic, a transtor amp ( set the level ) , a 555 in a monostable mode circuit ( I check the schematic ) will work also. So you program the Arduino to check an output pulse, when you have a pulse, activated an amplify tone and "reset" when everything is calm again.
You could use a motion/pressure sensor (under the baby's pillow, mattress, anything) and microphone together. When the microphone detects noise, if the pressure sensor is detecting changes in pressure, it could trigger what you want it to do. There could also be a button close by, so if you're getting the baby up in the morning, it disables it, and clicking it again enables it.