0.6 Jbs2020-square wave sound

Table of contents

• Preface
  • Viewing tip
    • Listings
• General background information
  • What is sound?
  • White noise
  • A square wave
    • An audio graph of a square wave
    • Points on graph
• Discussion and sample code
  • Three classes are unchanged
  • The class named MusicComposer05
  • The class named SquareWave
    • Beginning of the class named SquareWave
    • Beginning of the getMelody method
    • Required audio data format
      • Monaural, channels = 1
      • Stereo, channels = 2
    • Generating the square wave
      • Local working variables
      • Set the frequency of the square wave
      • Decompose val into two bytes
      • Populate the audio data array
• Run the program
• Miscellaneous
• Complete program listings

Preface

This module is part of a collection titled Accessible Objected-Oriented Programming Concepts for Blind Students using Java . It explains how to write a program that creates an audio output consistingof a 1000 Hz square wave.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find the listings while you are reading about them.

Listings

• Listing 1 . Beginning of the class named SquareWave.
• Listing 2 . Beginning of the getMelody method.
• Listing 3 . Local working variables.
• Listing 4 . Set the frequency of the square wave.
• Listing 5 . Decompose val into two bytes.
• Listing 6 . Populate the audio data array.
• Listing 7 . The class named AudioFormatParameters01.
• Listing 8 . The class named AudioPlayOrFile01.
• Listing 9 . The class named AudioSignalGenerator02.
• Listing 10 . The class named MusicComposer05.
• Listing 11 . The class named SquareWave.

General background information

What is sound ?

An earlier module titled Jbs2000-What is Sound? explained some of the physical characteristics of sound. It also explained that sound can beproduced when a computer program causes the diaphragms on audio speakers connected to the computer to move back and forth or vibrate.

White noise

An earlier module titled Jbs2010-Your First Sound Program explained how a random number generator can be used in a program to cause the speakerdiaphragms to move back and forth or vibrate in a random fashion producing what is commonly called white noise or pink noise. (Click WhiteNoise to hear a sample of white or pink noise. You should be able to play the audio file with any standard mediaplayer that can handle the AU file type. In case you are on the OpenStax site and you are unable to download the audio file, click the Legacy Site link at the top of this page to switch over to the same module on the Legacy site.You shouldbe able to download the audio file from there.)

White noise is totally unorganized or random. Beginning with this module, we will start applying more organization to the sound until we reach the pointwhere we can write a program that simulates a player piano. (Click Greensleeves to hear a simulation of a player piano.)

A square wave

In this module, we will write a program that attempts to cause the diaphragms to move back and forth instantaneously switching from one position to another by creatingaudio data based on a square wave. (Click SquareWave to hear a sample of a 1000 Hz square wave. A future module will compare the sound of a 1000 Hzsquare wave with the sound of a pure 1000 Hz sinusoidal tone.)