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NoteArc

A minimalistic guitar tuner and pitch detector

this project is my first android app and the submission for cs50 2020. thank you david and tommy !

created using

• TarsosDsp (TarsosDSP is a Java library for audio processing) .
• material.io for theming
• material-intro-screen for intro sequence.

Functionality

• Tune standard 6 string guitar (E A D G B E).
• Note detection , so that you can do other tunings aswell.
• frequency detection , using which tuning can be more accurate.
• minimalistic simple ui .

<img src="1.png" alt="1" width="200"/> <img src="2.png" alt="2" width="200"/> <img src="3.png" alt="3" width="200"/>

working

<img src="home.png" alt="1" width="300"/> Let's start with some really basic introduction to music theory and guitars. But at first we have to define some important musical terms as an exact distinction will avoid some ambiguities:

1. The frequency is defined as the reciprocal of the period duration of an repeating event. For example, if we have a sinusoidal signal with a period length of 2ms, the frequency is 500Hz.

2. Pitch is the perceived frequency of a sound. Thus, in contrast to frequency which is physical measure, the pitch is a psychoacoustical measure. This distinction is needed as there are cases where we hear frequencies which are physically not there (or don't hear frequencies which are actually there).

3. A note is just a pitch with a name. For example, the well known A4 is a pitch at 440Hz. It can also carry temporal information like whole notes or half notes, but this is rather uninteresting for us.

let take a look at guitar and how it works.

I guess most of you know this but the "default" guitar has 6 strings which are usually tuned in the standard tuning EADGBE. Whereby each note refers to one of the strings.

now , guitar has raised bars over fretboard called as FRETS. the distance between 2 frets is called as a HALF STEP.

fn = f0 * (2)^i/2

i- number of half steps between these two frequencies fn - current frequency f0 - standard frequecy now we use this formula to calculate HALF steps (i) from standard frequency f0.

for more info :- https://pages.mtu.edu/~suits/NoteFreqCalcs.html https://en.wikipedia.org/wiki/Equal_temperament

if we try to get i on one side , we get

12⋅log₂(fn/fo) = i

implementation

1 .

Now we take audio from mic and process it to find the fundamental frequency. before that , lets look at fundamental frequencies and algorithms to find it. as you can see , an instrument produces multiple frequecies even tho there is silence . to find the fundamental frequecie , you need pitch detecting algorithms

we will be using FFT_YIN , which is already provided in TarsosDsp library i mentioned before.

2 .

now we got the fundamental frequency , now we can use the formula i mentioned before to calculate the half steps .

using half steps , we can simple find the note and ocatave as we already know the standard frequency or the standard note

here, 440hz , A₄ note is the standard frequency . we can count the number of steps from there to find the current note.

click to learn more

3 .

now just match you current frequency to standard one to tune ;)