Pages: [1]   Go Down
Author Topic: Shield for raw audio acquisition  (Read 1600 times)
0 Members and 1 Guest are viewing this topic.
0
Offline Offline
Newbie
*
Karma: 0
Posts: 11
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hey guys,
according to you, there is some valid shield for Arduino capable of acquiring an audio signal?

For a interactive audio project we would like to use Arduino for audio acquisiton; for various reasons we are evaluating to avoid and external audio card.

I would like to put an audio jack on the shield and to be able at least to read the amplitude value of the signal on an analog input of the Arduino. All the needed computations will be made by software (by the MAX/MSP environment).

I found this shield
http://macetech.com/store/index.php?main_page=product_info&cPath=4&products_id=11
but it seems that it does not provide nthe raw signal amplitude but only average amplitude and peak values.

I found how construct by myself a circuit to read a general audio signal, like
http://interface.khm.de/index.php/lab/experiments/arduino-realtime-audio-processing/
the main point is to translate the amplitude of the signal in the analog range used by Arduino (0-5V). However there could be some pre-built shield..

Thanks so much!
Logged

0
Offline Offline
Jr. Member
**
Karma: 0
Posts: 64
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

interesting question....sorry, i have no pre-built shield that i can recommend....one must exist though.
i thought for a moment about it and it dawned on me that perhaps you could measure the voltage of your audio output that you want to connect to the arduino.  let`s say its 5v.  
an idea...to try.  not sure if it would work.....would be to take a
electrolytic capacitor rated for say 10v and connect the + lead of your audio input to it.  connect the other side of the lead - to ground perhaps through a 1 k resistor....just thinking out loud here.  try at your own risk.
then i would measure the voltage(signal) with a voltmeter on the ground side of the capacitor.  assuming it is readable and below 5 volts, put that in an analog port and be sure you have appropriate grounding between the circuit and the arduino.

now, that said -- as i understand it, a capacitor filters out ac.  sound is ac.  so what the capacitor is filtering out will then be the sound and will be passed to the ground side of the cap.  that should be suitable to pick-up on an analog port and get amplitude readings......or?    just thinking out loud and offering a possible seed to a simple creative solution.  hope it helps.

if that works, i would look up high pass and low pass filters and build a combination of capacitor-resistor  that feeds only the audible sound to your analog port.

disclaimer disclaimer disclaimer  -- i am no specialist, just thinking out loud and offering an idea.  perhaps it helps.
Logged

SF Bay Area
Offline Offline
Edison Member
*
Karma: 11
Posts: 1244
Arduino Ninja
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

My Shifty VU Shield is not going to help read a raw analog signal. It's essentially a precision rectifier used as a peak detector.

Additionally, the Arduino doesn't have enough input bandwidth to receive a raw analog signal (one, let alone four channels) and transfer it unaltered to the computer software.

External USB sound cards really are the ideal solution.
Logged

Unique RGB LED Modules and Arduino shields: http://www.macetech.com/store

SF Bay Area
Offline Offline
Edison Member
*
Karma: 11
Posts: 1244
Arduino Ninja
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I meant that since they are only trying to get audio into a computer to use with Max/MSP, they should use the normal methods of doing so. I haven't yet seen what purpose the Arduino has in this project.
Logged

Unique RGB LED Modules and Arduino shields: http://www.macetech.com/store

SF Bay Area
Offline Offline
Edison Member
*
Karma: 11
Posts: 1244
Arduino Ninja
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Less wild speculation over here, since we had actually exchanged some emails earlier this week...
Logged

Unique RGB LED Modules and Arduino shields: http://www.macetech.com/store

0
Offline Offline
Newbie
*
Karma: 0
Posts: 11
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Guys, thanks so much for your posts!!!
And macegr, thanks to answer also here smiley-wink

I think that the best thing is to try to explain you what I am doing.
I am trying to support a project of an electronic musician.
We are building an electronic instrument that should act as controller for live perfomance.

In particular we would like to acquire the signal produced by "playing"/"touching" four cords. The musician think that using simply headphones to acquire the signal can be enough. He tested heaphones with the input line of a standard audio card and they seems to provide a good signal for his purpose.

Actually I did not understand exactly what information about the audio signal he want; I am waiting for a clarification. Up to now, I think he need a "envelope follower".

The controller includes various sensors (for example membrane potentiometers), for this reason we are already using Arduino.
The general architecture I proposed uses Arduino as simply hardware controller to acquire the sensor data; all the needed computations are done by a PC connected to Arduino, running a specific MAX/MSP controlling patch.

As you think, I proposed him to use an external audio card to acquire the signal from headphones; however for packing considerations (to reduce the number of connections and requirements to use the controller from a PC) he asked me if we could use Arduino for such purpose (because we are already using it). Links like this
http://interface.khm.de/index.php/lab/experiments/arduino-realtime-audio-processing/
let me think that it is possibile to read the raw signal from arduino...
but according to your posts, it seems that if I need to sample accurately the signal, this can't be done with Arduino due to its limited computational capabilities.
Finally, the musician told me that the following shield should provide what he needs
http://www.andregoncalves.info/ag_blog/?page_id=61
I will ask to the musician what he exactly needs respect to the audio signal. And then I will write the answer here!

Thanks so much again guys!!!
« Last Edit: January 08, 2011, 05:45:23 am by diegobrn » Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 11
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

We need only the peaks of the envelope..
Logged

Pages: [1]   Go Up
Jump to: