1 Acoustic Sampling Of Instruments Dan Starr Capstone Design Project Advisors: Prof. Catravas Prof. Postow

2 Presentation Outline Project Description Primary Assumptions Project Modules:  Event Detection  Pitch Detection  Loop Combination  Pitch Shifting  Playback GUI Demo

3 Project Notes of any length (looping) Additional notes (C  C#, D, D#, E, F, F#)  (Pitch Shifting) Some Musical Effects  (Staccato, Slur, Dynamics) * Reduce Storage * Single-note, Acoustic Instrument Audio Sample Ability to play many more notes Series of Algorithms MATLAB

4 Assumptions All samples look approximately like this: Good recording equipment Good instrumentalist

5 Good sample Bad sample The world isn’t perfect…

6 Where we are… Project Description Primary Assumptions Project Modules:  Event Detection  Pitch Detection  Loop Combination  Pitch Shifting  Playback GUI Demo

7 Event Detection Single-note audio sample Event Detection Step 1: Create Outline Attack, Sustain, Release Sections

8 Step 2: Find Key Points Points A, E: easy Point B: Max of first ½ second of signal Point D:Point C: Same method as Point D, but draw line from D  B.

9 Pitch Detection Determine pitch (frequency) of sustain section  Purpose: replace sustain (1s) with single period (5ms) Method:  Perform Discrete Fourier Transform  Find lowest frequency component Determine corresponding musical note Time DomainFrequency Domain 261Hz (C4) * 52% decrease in required storage *

10 Where we are… Project Description Primary Assumptions Project Modules:  Event Detection  Pitch Detection  Loop Combination  Pitch Shifting  Playback GUI Demo We Have Extracted: Attack Release Single Period of Sustain

11 Loop Combination Take single period and loop it to create a sustain of any length Splicing Simply repeat waveform Frequency must be very accurate Good Bad True Period: 3.8ms Reported Period: 3.2ms

12 Loop Combination Crossfading Fade one period out while fading the next period in Bad Fade linear sinusoidal logarithmic time + +

13 Attack, Release Reattachment Problem: Solution: Merge attack/sustain, sustain/release

14 Where we are… Project Description Primary Assumptions Project Modules:  Event Detection  Pitch Detection  Loop Combination  Pitch Shifting  Playback GUI Demo We Have Extracted: Attack Release Single Period of Sustain And we can play: A note of any length

15 Simple: resample at different frequencies  Frequencies given in table  MATLAB has built in resample function Pitch Shifting Equal Temperament System of Musical Intonation NoteRatio Unison1:1 Minor 2 nd 1:1.059 Major 2 nd 1:1.122 Minor 3 rd 1:1.189 Major 3 rd 1:1.260 Perfect 4 th 1:1.335 Diminished 5 th 1:1.414 Perfect 5 th 1:1.498 Minor 6 th 1:1.587 Major 6 th 1:1.682 Minor 7 th 1:1.782 Major 7 th 1:1.888 Octave1:2 Typical Sampling Rate: 44.1 KHz

16 Instrument Name:  Consult stored names Note (A,F#,Gb):  Pitch shifting results in shorter samples  add more sustain to account for it *Note Length*  Problem: Length to be played is less than length of attack.  Solution: Create new linear release Playback Instrument Name Note Note length Sound Playback

17 GUI DEMO