Method 2: find time different by using interrupt

Figure 1: interrupt output

I find that it can be done by using interrupt in Arduino Uno. By using interrupt, it can find times tamp more accurately by utilize micros(). However, it has only 2 interrupt pin in Arduino Uno, to further development, it needs to be used Arduino Mega which has 6 interrupt pins. 

Sound generator

To produce a sound, I choose MSP-430 launchpad to generate audio sound.

Figure 1

In order to easily using code example , I use the integrated development environment called Energia. 

It is based on Arduino framework so it can be easily to understand in my project stage.

Time Different of arrival between different Sensor Output

Figure 1

The above figure shows that when the sound source near the mic2 instead of mic1, sound at mic2 will receive earlier than mic1 which is counted a smaller micro seconds.

In fact, each analogRead takes around 100 microseconds, which may make a significant error. However, the speed of sound is 343.2 metres per second (1,126 ft/s). The sound would travel only 0.1126 feet during an analogRead() in 100 microseconds.

To implement the circuit hence to receive enough signal, I use four microphone modules which shows in the following.

Figure 2

Figure 3

However, in figure 3, there are some error appointed. Mic4 always acquire signal at the first time although the sound source near mic2.

Sound Sensor Output

Figure 1: output of audio sensor

As the audio input is just a value, I try to implement this to another format in order to trigger the sound localization easily and more sensitive.

This program shown the loud sound or quiet on the serial monitor.

Figure 2: multiple output of audio sensor

As calculation of time different of arrival needs two time of arrival in two different sound sensors. I try to implement two sensor input in Arduino. Since I speak near mic1 instead of mic2, "LOUD,LOUD" message will display on mic1 first. Besides, since I speak near mic2 instead of mic1, "LOUD,LOUD" message will display on mic2 first.

sound module testing

Figure 1: sound module

I had bought sound module for sound acquisition. It need 3.3V to 5V and <10mA for working. It can adjust the sensitive by changing angle of bolt hole

Figure 2: output of sound module (no sound)

Figure 3: output of sound module (sound pulse)

Figure 4: output of sound module (no sound pulse)

Figure 5: output of sound module (sound pulse)

Figure 6: output value of sound module

Serial monitor with baud rate 9600 Hz
It can be detecting the sound by detecting voltage level at output pin in sound module