Computer Music: Musc 216
JSYD Tutorial 5
Adjusting the AMPLITUDE

The amplitude of the output of your patch is determined by a parameter in the Oscillator operator.  Using the simple patch you created in the 1st tutorial (Creating a Simple JSYD Patch):

  • Select the Oscillator operator.
  • You should see this window:

    •  

          

      The default value in the Amplitude field is "1" -- change this to .5

      Note the frequency of 440 Hz.  The wave form is a SINE wave.
       
  • MAKE SURE YOU HAVE ENTERED .5 (that's "point - 5") in the AMPLITUDE field.
  • Click the SYNTHESIZE button at the top left corner of the patch window.  You will not hear the sound of the patch until you "synthesize" it.
  • Make sure your headphones are connected to the audio output of the computer.  Also, it is assumed that you have already checked the system audio settings and your computer will produce audio output.  PLEASE make sure you have entered a fractional (percentage) value into the amplitude field of the Oscillator parameter field.  If you enter a number greater than 1 (100% - Unity), you may produce a sound that is so loud that it may damage your hearing if your headphones are placed directly over you ears. Be cautious and place your headphones in front of your ears until you become familiar with this setting.
  • When you are ready to proceed, click the PLAY button at the top left corner of the patch window.  You should hear the SINE wave play in your headphones. Or, click the link below to hear sound.

    Sine.aiff

FURTHER EXPERIMENTS: Try changing other values in the Oscillator parameters window, particularly the waveform. However, if you select SQUARE wave instead of SINE wave, the perceived LOUDNESS will be much greater. So, you should set the amplitude of a SQUARE wave at about HALF that of a sine wave. What would cause this effect?

To answer this question, draw a SQUARE wave along side a SINE wave on a sheet of graph paper.  The SQUARE wave stays at the peak amplitude for a longer period of time than the SINE wave.  Consequently, it has a greater average amplitude. It may seem like this proves the point -- but it doesn't. Draw a TRIANGLE wave beside a SINE wave and compare the overall average amplitudes. The TRIANGLE wave actually has an average amplitude LESS than a SINE wave but it has a greater perceived loudness. Consequently, something else must be going on.

Perceived loudness in tones with the same frequency is linked to the COMPLEXITY of the waveform -- that is, how many HARMONICS. The more harmonics, the greater the perceived loudness. The SQUARE wave is a more COMPLEX sound than a SINE wave because it contains many harmonics. Compare the two sounds:

Sine.aiff
Square.aiff

The SINE wave has no harmonics. For further understanding of this phenomenon see:

Fourier Analysis
Constructive Interference

Remember, you have to RE-SYNTHESIZE the patch after every parameter change in order to hear the result.

IT IS NOT RECOMMENDED THAT YOU SET THE AMPLITUDE OF THE OUTPUT TO A VALUE GREATER THAN 1.0.   IF YOU DO, MAKE SURE THAT YOU REMOVE YOUR HEADPHONES.

ALSO, IF YOU CHOOSE A WAVEFORM WITH A HIGH INTENSITY (SQUARE, SAW, ETC.) THE PERCEIVED LOUDNESS WILL BE MUCH GREATER THAN A SINE WAVE.   KEEP THE AMPLITUDE LESS THAN .5 (50%) and even as low as .15 (15%). IF YOU INCREASE THE AMPLITUDE OF A SQUARE WAVE > 50% THEN MAKE SURE THAT YOU REMOVE YOUR HEADPHONES.

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