we are testing the output of a sketch using the MAX4466 microphone for Arduino. The sketch is the following:
Code: Select all
const int sampleWindow = 50; // Sample window width in mS (50 mS = 20Hz)
unsigned int sample;
void setup()
{
Serial.begin(9600);
}
void loop()
{
unsigned long startMillis= millis(); // Start of sample window
unsigned int peakToPeak = 0; // peak-to-peak level
unsigned int signalMax = 0;
unsigned int signalMin = 1024;
// collect data for 50 mS
while (millis() - startMillis < sampleWindow)
{
sample = analogRead(0);
if (sample < 1024) // toss out spurious readings
{
if (sample > signalMax)
{
signalMax = sample; // save just the max levels
}
else if (sample < signalMin)
{
signalMin = sample; // save just the min levels
}
}
}
peakToPeak = signalMax - signalMin; // max - min = peak-peak amplitude
double volts = ((peakToPeak * 3.3) / 1024) * 0.707; // convert to volts
double first = log10(volts/0.00631)*20;
double second = first + 94 - 44;
Serial.println("misurazione "+String(second));
}
Probably we are missing something obvious but still we ask if you are aware of something we can add/remove from the code. What is strange, is that it is very precise above a certain level of dB.
Thank you very much,
Regards
Fabio Ricci