TiltFilter

Overview

Variable slope tilt filter

Discussion

This subsystem implements a filter with the desired slope over the specified band. The intended application is for filtering white noise to produce noise of a desired color. Common noise colors include Violet, Blue, White, Pink, and Red, with respective slopes of +6, +3, 0, -3, and -6 dB/octave. Arbitrary slopes, such as -7.15 dB/octave can also be used. fStart specifies the frequency at which the slope begins, while fStop specifies the frequency at which the slope ends. avgPower specifies the squared 2-norm of the filter. This is used to preserve the area under the frequency response curve, regardless of the desired slope. The underlying filter is implemented as a cascade of biquad stages. The default number of stages is set to 3, allowing for slopes ranging from -18 to +18 dB/octave. The number of biquad stages can be adjusted by right-clicking the Tilt Filter module in Audio Weaver Designer and selecting the "Module Name and Arguments..." option.

Module Pack

Advanced

ClassID

classID =

Type Definition

typedef struct _ModuleTiltFilter
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
} ModuleTiltFilterClass;

Variables

Properties

Name	Type	Usage	Default Value	Range	Units
slope	float	parameter	0	-18:18	dB/octave
fStart	float	parameter	1000	1:20000	Hz
fStop	float	parameter	20000	1:20000	Hz
avgPower	float	parameter	0	-20:20	dB
numStages	int	const	3	Unrestricted

Pins

Input Pins


Name	in
Description
Data type	float
Channel range	Unrestricted
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real

Output Pins


Name	out
Description
Data Type	float

Scratch Pins


Channel Count	1
Block size	32
Sample rate	48000

Matlab Usage

File Name: tilt_filter_subsystem.m 
 SYS = tilt_filter_subsystem(NAME, NUM_STAGES) 
 Implements a tilt filter which attenuates frequencies based on a specifed 
 slope in dB/octave.  Arguments: 
    NAME - name of the module. 
    NUM_STAGES - number of Biquad stages used internally.  By default this 
                 equals 3.