Processing Sound Ranges part 3

1. Processing Sound Rangespart 3 Barb Ericson Georgia Institute of Technology Oct 2009 UsingSoundRanges-part3

2. Learning Goals • Processing ranges of Sound values • Creating echoes • Changing the sound frequency • Computing concepts • Changing a for loop to increment by a value other than 1 • Modifying a method to be more general UsingSoundRanges-part3

3. Echo • By blending a sound with itself we can make an echo • Add the sound values to the same sound but after some delay UsingSoundRanges-part3

4. Method echo public void echo(int delay) { // make a copy of the original sound Sound s = new Sound(this.getFileName()); int value = 0; // loop from delay to end of sound for (int i = delay; i < this.getLength(); i++) { UsingSoundRanges-part3

5. Method echo continued /* get the value back by delay samples from the * copy of the sound and make it fainter*/ value = (int) (s.getSampleValueAt(i-delay) * 0.6); /* set the value at the current index to the sum * of the current value and the echo*/ this.setSampleValueAt(i, this.getSampleValueAt(i) + value); } } UsingSoundRanges-part3

6. Test the echo method String fileName = FileChooser.getMediaPath( "thisisatest.wav"); Sound sound = new Sound(fileName); sound.explore(); sound.echo(20000); sound.explore(); UsingSoundRanges-part3

7. How does that work? • The echo method takes an integer delay • The number of samples to wait before starting the echo • It makes a copy of the current sound • So that we copy without the echo • Loop starting from delay to the end of the sound • Get the value at i-delay and multiply it by 0.6 to make it quieter • Set the current sound value at i to the current value at i plus the calculated value UsingSoundRanges-part3

8. Creating Multiple Echoes • You can use a nested loop to create multiple echoes • Here is an example nested loop in Alice UsingSoundRanges-part3

9. Creating Multiple Echoes Method public Sound echo(int delay, int numEchoes) { int soundLength = this.getLength(); Sound echoSound = new Sound(numEchoes * delay + soundLength); int value = 0; int echoIndex = 0; int echoValue = 0; double echoAmplitude = 1; // to start // copy the original sound echoSound.splice(this,0,soundLength,0); /* loop starting with 1 to create the first echo at the * right place and end when = the number of echoes */ UsingSoundRanges-part3

10. Multiple Echoes - continued for (int echoCount = 1; echoCount <= numEchoes; echoCount++) { // decrease the volume (amplitude) of the echo echoAmplitude = echoAmplitude * 0.6; // echo the whole sound for (int i = 0; i < soundLength; i++) { echoIndex = i + (delay * echoCount); echoValue = (int) (this.getSampleValueAt(i) * echoAmplitude); echoSound.setSampleValueAt(echoIndex,echoValue + echoSound.getSampleValueAt(echoIndex)); } } return echoSound; } UsingSoundRanges-part3

11. Try Multiple Echoes Sound s = new Sound( FileChooser.getMediaPath("croak.wav")); Sound e = s.echo(8000,5); e.play(); UsingSoundRanges-part3

12. The frequency of a wave is the number of cycles per second (cps), or Hertz (Hz) (Complex sounds have more than one frequency in them.) Our perception of pitch is related (logarithmically) to changes in frequency Higher frequencies are perceived as higher pitches We can hear between 5 Hz and 20,000 Hz (20 kHz) A above middle C is 440 Hz Changing the Sound Frequency UsingSoundRanges-part3

13. Double the Frequency • If we take every other sample we double the frequency of the sound • Completes two cycles instead of one in the same time • It will sound higher 100 | 200 | 300 | 400 | 500 100 | 300 | 500 | 0 | 0 UsingSoundRanges-part3

14. Double Frequency Method public void doubleFreq() { // make a copy of the original sound Sound s = new Sound(this.getFileName()); /* loop and increment target index * by one but source index by 2, * and set target value * to the copy of the original sound */ UsingSoundRanges-part3

15. Double Frequency - Continued for (int sourceIndex=0, targetIndex = 0; sourceIndex < this.getLength(); sourceIndex=sourceIndex+2, targetIndex++) this.setSampleValueAt(targetIndex, s.getSampleValueAt(sourceIndex)); // clear out the rest of this sound to silence (0) for (int i = this.getLength() / 2; i < this.getLength(); i++) this.setSampleValueAt(i,0); } UsingSoundRanges-part3

16. Test Double Frequency Sound s = new Sound(FileChooser.getMediaPath( "c4.wav")); s.explore(); s.doubleFreq(); s.explore(); UsingSoundRanges-part3

17. Challenge • Create a method that will take every third sample • Will this sound higher or lower? • Can you make this method more general? • By passing in the amount to add to the source index each time? UsingSoundRanges-part3

18. Halving the Frequency • We can copy each source value twice to half the frequency • Only get through half a cycle in the same time we used to get through a full cycle • It will sound lower 100 | 200 | 300 | 400 | 500 100 | 100 | 200 | 200 | 300 UsingSoundRanges-part3

19. Halve Frequency Method public void halveFreq() { // make a copy of the original sound Sound s = new Sound(this.getFileName()); /* loop through the sound and increment target index * by one but source index by 0.5 and set target value * to the copy of the original sound */ for (double sourceIndex=0, targetIndex = 0; targetIndex < this.getLength(); sourceIndex=sourceIndex+0.5, targetIndex++) this.setSampleValueAt((int) targetIndex, s.getSampleValueAt((int) sourceIndex)); } UsingSoundRanges-part3

20. Testing Halve Frequency Sound s = new Sound(FileChooser.getMediaPath( "c4.wav")); s.explore(); s.halveFreq(); s.explore(); UsingSoundRanges-part3

21. Challenge • Write a method that will copy each sound value 4 times to the target • Will the new sound be higher or lower? • Can you make this more general? • By passing in the number of times to copy the source value • Try it with 3 times and check the index values to make sure that you are doing it right UsingSoundRanges-part3

22. Summary • You can increment or decrement loop variables by numbers other than 1 • You can make methods more general • By passing in parameters UsingSoundRanges-part3