Technical data

DOC-01-TELAS-CRG-4 ASTi ACE Studio Components Reference Guide Rev.M
34 Copyright © 2014 Advanced Simulation Technology inc.
2.14. Noise Source
Summary: The Noise Source component generates a filtered white, pink, or brown
noise signal. The type of filtering applied may be lowpass, bandpass, or highpass.
The filter quality factor, rolloff frequency, and gain can be controlled by input
variables from elsewhere in the model or from the host interface. The noise signal
is an internal pseudo random noise source, providing an improved noise source
with better tunability.
Description: This component consists of a signal source and a filter. The source
signal on which the filter acts is white guassian, pink, or brown noise. The noise
signal should be active only if the derived OutGain is greater than 0.0.
The filter is controlled by the parameters: Enable, Type Filter Frequency, and Q
factor. The Filter Enable control is specified by an externally controlled variable
and an XOR logic gate control. XOR logic is applied to the external variable value
and the gate control to derive a final value for the Filter Enable flag. If no external
variable is connected, the value of the logic gate control becomes the Filter Enable
flag. If Filter Enable is set to False, no filtering is applied to the noise signal.
Type determines the type of filter applied to the input signal (Off, Lowpass,
Highpass, or Bandpass). If Type is set to Off, no filtering should be applied to the
noise. Filter Frequency (in Hertz) provides the rolloff frequency of the filter. The
meaning of the frequency depends on the filter type as follows:
Filter TypeFrequency Meaning
OffIgnored
LowpassUpper bound frequency
HighpassLower bound frequency
Bandpass Center frequency with bandwidth controlled by Q Factor (See below)
Q Factor is the filter quality factor, which effectively determines the filter rolloff for
lowpass and highpass filters and the filter bandwidth for bandpass filters. Q Factor
is inversely proportional to the filter rolloff or bandwidth.
The filter parameters are used to drive the filter coefficients for a 2-pole IIR filter.
If Q Factor is 0 or less, a very low non-zero value should be used for the k
calculation. The output from the filter is active only if the noise source is active. If
the Filter Type is Off, the filter output signal is the input signal.
An amplitude gain control is applied to the filter output. This output gain control
consists of a connection to an external controlled variable and a scale factor. The
value of the external variable is multiplied by the scale factor to derive the output
gain. If no external variable is connected, the value for the scale factor becomes
output gain.
The Noise Source component output audio should only be active if the following
conditions are true:
I. The output from the filter is active.
II. The derived output gain (external variable * scale factor) is greater than 0.0.
Control Inputs
FilterEn-
able
Type Default Value
boolean FALSE
Description: FilterEnable is a flag that determines if the white noise
signal is filtered. If no external control is connected to FilterEnable,
the XOR modifier is used as the FilterEnable value.
Modifier: XOR
Modifier_default: True