Syd Helicopter Tutorial
(Version 108b2.1)

 

Creating a SYD Patch which simulates the sound of a HELICOPTER Back to Tutorials Menu
 

Your window should look something like this:
 

 
 
 

The RANDOM NOISE GENERATOR creates NOISE such that all frequencies and all amplitudes are randomly giving a steady output of what would sound like 'radio static.'

The BUTTERWORTH FILTER is a variable band filter which allows four types of filtering:

    - High Pass
    - Low Pass
    - Band Pass
    - Band Reject

Double-click on the BUTTERWORTH FILTER to open its edit window.  It should look like this:


 

Set the values in the various fields so they show these values.  Specifically, random noise will be passed to the filter.  However, only a specific frequency of noise will be allowed to pass through (400 Hz).  The BAND 'width' will be controlled by the variable, Ctl1.  Think of the  BAND WIDTH as the filter's amplitude -- the wider the band, the more noise passes through centered around the specific frequency contained in the FREQ field.  In other words, the wider the band, the louder the noise.  The value in the FREQ field controls the apparent pitch of the noise.  A high value would allow 'high-pitched' noise to pass through.  A low value would allow 'low pitched' noise to pass through.

Set the values in the BUTTERWORTH FILTER as pictured above and then click OK.

Specifically, you are setting the:

Now, drag an OSCILLATOR OPERATOR down into the window.  Connect the output of the OSCILLATOR OPERATOR to the BUTTERWORTH FILTER.

Click and hold on the above connection and then select the connection type as: ALT CONTROL SIG#1 [Ctl1].  See below for detail:
 


 
 

Set the parameters of the OSCILLATOR OPERATOR to these values:  Freq: 10; Amplitude: 200 (this oscillator will contol the bandwidth of the filter by adding and subtracting 200 to the band width, thereby opening and closing the bandwidth).

Save your file.

Make sure the MAIN OUTPUT OPERATOR is set to MEMORY and not to FILE.

Synthesize your patch and then play it.  It should sound like this (click below):

Helicopter1.aiff

 

Explanation for including an offset in the Butterworth Filter Band field:

In the above patch, you are using a sine wave Oscillator to control the opening and closing of the bandwidth of the Butterworth Filter. This is what creates the characteristic oscillation of the 'Helicopter' sound. If you send just the control signal (ctl1) to the Band parameter field, then the Oscillator would send all values of the Sine Wave (positive and negative) to the Bandwidth parameter field.

 

 

To cancel out the negative values of the Sine Wave (0 thru -200), use an 'offset' in the Filter Bandwidth parameter field which is equivalent to the AMPLITUDE of the modulating Sine Wave:


 

If you had trouble understanding any part of the Helicopter Patch tutorial above, you may want to repeat earlier parts of the SYD TUTORIALS.

 

Variations on the Basic Helicopter Patch: Lowpass Filter

A helicpoter sound can also be achieved by using the LOWPASS filter instead of the BANDPASS filter. However, this requires a slightly different technique:

When using the BANDPASS filter, the helicpoter effect is achieved by modulating the BANDWIDTH with a low frequency oscillator (LFO).

When using the LOWPASS filter, the helicpoter effect is achieved by modulating the CUTOFF FREQUENCY with a low frequency oscillator (LFO). You will still need to use an 'offset' to compensate for the negative values generated by sine wave (see above). Try this:

Use the same basic patch as described above. Keep the settings of the modulating oscillator the same (frequency = 10; amplitude = 200).

However, the parameter settings for the Butterworth filter will look like this:

When the patch is synthesized, it should sound like this: Helicopter2.aiff

Compare with the original helicopter patch above:Helicopter1.aiff

 

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