FM Synthesis |
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You can use the FM Synthesis dialog to create complex sounds from simple waveforms using frequency modulation (FM). To display this dialog, choose Synthesis from the Tools menu, and choose FM from the submenu.
In frequency modulation, the frequency of a waveform (the carrier) is modulated by the output of another waveform (the modulator) to create a new waveform. If the frequency of the modulator is low, the carrier will be slowly de-tuned over time. However, if the frequency of the modulator is high, the carrier will be modulated so quickly that many additional frequencies, or sidebands, are created.
In Sound Forge, up to four waveforms (operators) can be used in a variety of configurations. Depending on the configuration, a waveform can be a carrier, a modulator, or a simple, unmodulated waveform.
From the Tools menu, choose Synthesis, and choose FM from the submenu.
In the Total output waveform length box, specify the length (in seconds) of the generated waveform.
Drag the Configuration slider to determine the arrangement and number of operators to be used.
Modify each operator as desired.
Choose a position from the Insert waveform at drop-down list to specify where the generated waveform will be placed within the existing sound file.
Click the OK button.
When you drag the Configuration slider, a graphical representation of the arrangement and number of operators that will be used is displayed:
The outputs of operators joined horizontally are simply mixed together. The outputs of the bottom operators are mixed together to form the final output. Mixing different simple waveforms is called additive synthesis.
Operators joined vertically are FM carrier-modulator pairs. The bottom operator is the carrier, and the top operator is the modulator.
Operators that have no other operator directly above are simple waveform generators.
When three or more operators are stacked, the top operator modulates the operator below it, which modulates the following operator, and so on.
Click a Current operator radio button to choose the operator that you want to modify.
Adjust the envelope graph to modify the amplitude of the operator over time.
Click the left mouse button to define a point and drag to change its position. Click the right mouse button or double-click the left mouse button over an existing point to remove the point. You can create up to 8 envelope points for each operator.
Click the Reset button to reset the envelope and remove all but the outermost two envelope points.
Choose a waveform shape from the Operator shape drop-down list.
In the Frequency box, specify the frequency of the operator.
Notes:
If Frequency is set to 0.00, a DC (zero-frequency) waveform is produced regardless of the waveform specified.
When you choose Noise from the Operator shape drop-down list, Frequency determines the high-frequency content of the noise. For full-bandwidth (white) noise, set Frequency to its highest possible setting.
Drag the Feedback slider to determine the amount of the operator's output that is used to modulate itself. If the operator is also being modulated by another waveform, the feedback path and the modulator output are mixed together to modulate the carrier.
Drag the Amplitude fader to determine the output gain that will be applied to the current operator after the amplitude envelope.
If the operator is a modulator, this control, along with the envelope, determines the amount of frequency modulation applied to the carrier. If the amplitude of a modulator is high, very harsh sounds can result.
For more information about using processing dialog controls, click here.