# The Synthetic Psychology of Sound Localization

Posted on Feb 6, 2014

Although the voltage across the two pins of our microphone will fluctuate based on the input sound, we would like to amplify this so that the Arduino can actually read the signal. This can be a bit of a complex circuit to think about at first to we will build it up slowly. This figure gives an overview of what the circuit will do: First, the volta

ge changes due to the mic (step 3 in the figure) are relatively small (fractions of a millivolt usually) we would first like to move them into a better range to use as input to our amplifier (step 4 in the figure). We`ll do this a couple times in the lab and refer to it as "stepping up" the signal, since we are changing the average voltage value without changing the variance. The amplifier stage will "turn up the volume" on the voltage changes by making them span a larger range (step 5). Thinking back to your statistics class, this step does effect the variance! The output of the amplifier will be centered at 0V and range positively and negatively. However the Arduino can only read positive values in the range 0-5V. Thus, in the final stage, we will "step up" the signal again to range between 0V and 5V (step 6 in the figure) which is the type of input signal that the Arduino analogRead() function is designed to measure (step 7 in the figure). In order to add the microphone to the Arduino, we need a basic microphone circuit that provides voltages with the appropriate values. This will cover steps 1-4 in the overview above. A classic way to do this is with a "voltage divider" circuit (see below). A voltage divider simply involves a voltage source (e. g. , battery, or in our case the +5V pins on the Arduino chip) and two resistors. The resistor are connected in series (i. e. , in a row or sequence. if the wires are the...

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