retrolefty:
Stronk:
Thanks for the fast reply!
I havn't thought about that. Ye, I know that the audio is a voltage of variable amplitude and frequencies. But I'm not so into the AC/DC part... We made a amplifier to the mic and it works good with amplitude. But do we need other amplifier to sample frequency?No your understanding of electronics is lacking. The audio signal from the microphone contains both the amplitude information and the frequency information. Your software will have to perform the various extraction methods of the information you seek from the composite audio AC signal.
This should be the same amplifier as we have at the moment: http://www.electrokit.com/mikrofonforstarkare.46099
Well that amp lists it's output voltage as 300 millivolts max from the microphone signal. That means if will not use up much of the voltage measurement range of an arduino analog input pin which is 0-5vdc, so you are only going to have 6% of the measurement range in effect. Also the 300 millivolts is still an AC voltage and again an arduino pin cannot safely measure the negative portion of a AC signal without risking damage to the input pin. A 300 millivolt signal means the voltage can vary anywhere within a +150 millivolt to a -150 millivolt range, and the arduino analog input pin cannot handle the 0 to -150 millivolt part. So usually you will see a opamp buffer stage added to allow a DC offset value to be added to the AC signal such that the total positive and negative peaks values of the audio signal are contained within a DC 0-5vdc range.
I only bring these issue up because before you can have any success with your software methods you first must have the electrical interface proper or you will just end up with a lot of frustration as garbage in will always result in garbage out. I would suggest you search the web for projects that already perform what you are trying to do and look at how they handled both the electrical side and the software side.
Good luck;
Lefty
KeithRB:
I know it is fun to do your own FFT, but this chip does all the work for you, too bad it is backordered:
Graphic Equalizer Display Filter - MSGEQ7 - COM-10468 - SparkFun Electronics
Hehe, I know my understanding of electronics is lacking. It's our first time we do something like this practical in school... And we've never done anything with microphones and amplifiers... No wonder? But we're still going to do this because we want to learn!
So what I've understand is that we need a stronger audio signal from the amplifier who can do 0-5VDC and not 0-0.3VDC as our does? And to to that easy, is to replace the chip to something that KeithRB mentioned? Again, electronics are sadly not our best section... We suck at it.