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- <p align="center">
- <b>Guitar and Bass Tuner Library v3.3</b><br>
- <b>Teensy 3.1/2</b><br>
- </p>
-
- >Software algorithm ([YIN]) for guitar and bass tuning using a Teensy Audio Library. This audio object's algorithm can be some what memory and processor hungry but will allow you to detect with fairly good accuracy the fundamental frequencies f<sub>o</sub> from electric guitars and basses.
- >>You can install this as a normal Arduino Library and will work with the Audio Library, no need to edit the Audio libraries source now.
-
- <!-- language: lang-none -->
- Hookup Guide - ~.6v DC Bias and High Pass Filter - No Amplification
-
- *--------------------------------------------------*
- | |
- | Pull Down Resistor | ' | |
- *------------/\/\/\-------------* |' '| |
- | 47K | _|_'_|_ |
- | | |` ` ` `| |
- *---)|+---* | | ` ` ` | |
- | 10uF | | |` ` ` `| |
- TEENSY 3.1 | | | | ` ` ` | |
- _______________ *-/\/\/\--* | |` ` ` `| |
- |GND |_____| Vin| | 2.2K | | | ` ` ` | |
- |0 ----- AGND|<-* | | |` ` ` `| |
- |1 |`````| 3.3V|>---/\/\/\--*--/\/\/\--* | | ` ` ` | |
- |2 | | 23| 10K 47K | | |` ` ` `| |
- |3 ----- 22| | | | ` ` ` | |
- |4 |'| 21| | | \=====/ |
- |5 ------ 20| | | | '`| |
- |6 |::::::::| 19| | REMOVE | | S`| |
- |7 |::::::::| 18| | DC | | H`| |
- |8 |::::::::| 17| | BIAS | | I`| |
- |9 ------A2/16|<---SIGNAL-.6v-BIAS----*---+|(----* | E`|>--ANGD--*
- |10 --- 15| .6VDC 10uF | | L`|
- |11 |(`)| 14| | | D`|
- |12 --- 13| | | `|
- --------------- | |===|
- | \_/
- | /T\
- | .-I-.
- *---<\ P /
- \_/
-
- >Many optimizations have been done to the [YIN] algorithm for frequencies between 29-400Hz.
- >>While its still using a brute force method ( n<sup>2</sup> ) for finding the fundamental frequency f<sub>o</sub>, it is tuned to skip certain <b>tau</b> (<img src="http://latex.numberempire.com/render?%5Cinline%20%5Chuge%20%5Cmathbf%7B%5Ctau%7D&sig=845639da85c0dd8e2de679817b06639c"/></img>) values and focus mostly on frequencies found in the bass and guitar.
- >>>The input is double buffered so while you are processing one buffer it is filling the other to double throughput.
- >>>>The parameter AUDIO_BLOCKS below can be adjusted but its default of 24 I found to be best to work with the guitar and bass frequency range (29- 400)Hz.
- >>>>>Looking into finding the Auto Correlation using FFT and IFFT to speed up processing of data! Not that simple because the YIN algorithm uses a squared difference tweak to the Auto Correlation.
-
- <h4>AudioTuner.h</h4>
-
- ```
- /***********************************************************************
- * Safe to adjust these values below *
- * *
- * This parameter defines the size of the buffer. *
- * *
- * 1. AUDIO_GUITARTUNER_BLOCKS - Buffer size is 128 * AUDIO_BLOCKS. *
- * The more AUDIO_GUITARTUNER_BLOCKS the lower *
- * the frequency you can detect. The default *
- * (24) is set to measure down to 29.14 Hz *
- * or B(flat)0. *
- * *
- * 2. MAX_COEFF - Maxium number of coefficeints for the FIR filter. *
- * *
- ***********************************************************************/
- #define AUDIO_GUITARTUNER_BLOCKS 24
- #define MAX_COEFF 200
- /***********************************************************************/
- ```
-
- <div>
- <b>YIN Algorithm</b>
- <ol>
- <li><b>Difference Function -</b> Squared difference of the (signal - signal lag(<img src="http://latex.numberempire.com/render?%5Cinline%20%5Chuge%20%5Cmathbf%7B%5Ctau%7D&sig=845639da85c0dd8e2de679817b06639c"/></img>))<br>
- <img src="http://latex.numberempire.com/render?%5Chuge%20d_%7Bt%7D%20%5Cbig%28%20%5Ctau%20%5Cbig%29%20%3D%20%5Csum_%7Bj%3D1%7D%5EW%20%20%5Cbig%28x_%7Bj%7D-x_%7Bj%2B%5Ctau%7D%5Cbig%29%5E%7B2%7D&sig=da6a2a10a134437679df399dbb9327df" /></li>
-
- <li><b>Cumulative Mean Normalized Difference Function -</b> Calculate the cumulative mean on the normalized difference signal<br><img src="http://latex.numberempire.com/render?%5Cinline%20%5Chuge%20d%27_%7Bt%7D%20%5Cbig%28%20%5Ctau%20%5Cbig%29%20%3D%5Cbegin%7Bcases%7D1%2C%20%26%20%5Ctau%20%3D%200%5C%5Cd_%7Bt%7D%20%5Cbig%28%20%5Ctau%20%5Cbig%29%5Cdiagup%20%26%5Cleft%5B%28%5Cfrac%7B1%7D%7B%5Ctau%7D%29%5Csum_%7Bj%3D1%7D%5E%5Ctau%20%20d_%7Bt%7D%20%28j%29%5Cright%5D%5Cend%7Bcases%7D&sig=15a0b31a37bd5db3074f854711119bb3" /></li>
- <li><b>Absolute Threshold -</b> Fix for subharmonic error with Autocorrelation, choose (<img src="http://latex.numberempire.com/render?%5Cinline%20%5Chuge%20%5Cmathbf%7B%5Ctau%7D&sig=845639da85c0dd8e2de679817b06639c"/></img>) that gives a minimum <img src="http://latex.numberempire.com/render?%5Chuge%20d%27&sig=ec41ac0239b48a3c53617da8e4ca64c7"/></li>
- </ol>
- </div>
-
- [YIN]:http://recherche.ircam.fr/equipes/pcm/cheveign/pss/2002_JASA_YIN.pdf
- [Teensy Audio Library]:http://www.pjrc.com/teensy/td_libs_Audio.html
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