fdesign.parameq

(To be removed) Parametric equalizer filter specification

Compatibility

Note

The fdesign.parameq filter specification object will be removed from DSP System Toolbox™ in a future release. Existing instances of the object continue to run. For new code, use the designParamEQ (Audio Toolbox) function instead. For more information on how to update your existing code, see Compatibility Considerations.

Syntax

d = fdesign.parameq(spec, specvalue1, specvalue2, ...)
d = fdesign.parameq(... fs)


Description

d = fdesign.parameq(spec, specvalue1, specvalue2, ...) constructs a parametric equalizer filter design object, where spec is a non-case sensitive specification character vector. The choices for spec are as follows:

• 'F0, BW, BWp, Gref, G0, GBW, Gp' (minimum order default)

• 'F0, BW, BWst, Gref, G0, GBW, Gst'

• 'F0, BW, BWp, Gref, G0, GBW, Gp, Gst'

• 'N, F0, BW, Gref, G0, GBW'

• 'N, F0, BW, Gref, G0, GBW, Gp'

• 'N, F0, Fc, Qa, G0'

• 'N, F0, Fc, S, G0'

• 'N, F0 ,BW, Gref, G0, GBW, Gst'

• 'N, F0, BW, Gref, G0, GBW, Gp, Gst'

• 'N, Flow, Fhigh, Gref, G0, GBW'

• 'N, Flow, Fhigh, Gref, G0, GBW, Gp'

• 'N, Flow, Fhigh, Gref, G0, GBW, Gst'

• 'N, Flow, Fhigh, Gref, G0, GBW, Gp, Gst'

where the parameters are defined as follows:

• BW — Bandwidth

• BWp — Passband Bandwidth

• BWst — Stopband Bandwidth

• Gref — Reference Gain (decibels)

• G0 — Center Frequency Gain (decibels)

• GBW — Gain at which Bandwidth (BW) is measured (decibels)

• Gp — Passband Gain (decibels)

• Gst — Stopband Gain (decibels)

• N — Filter Order

• F0 — Center Frequency

• Fc— Cutoff frequency

• Fhigh - Higher Frequency at Gain GBW

• Flow - Lower Frequency at Gain GBW

• Qa-Quality Factor

• S-Slope Parameter for Shelving Filters

Regardless of the specification chosen, there are some conditions that apply to the specification parameters. These are as follows:

• Specifications for parametric equalizers must be given in decibels

• To boost the input signal, set G0 > Gref; to cut, set Gref > G0

• For boost: G0 > Gp > GBW > Gst > Gref; For cut: G0 < Gp < GBW < Gst < Gref

• Bandwidth must satisfy: BWst > BW > BWp

d = fdesign.parameq(... fs) adds the input sampling frequency. Fs must be specified as a scalar trailing the other numerical values provided, and is assumed to be in Hz.

Examples

Design a Chebyshev Type II parametric equalizer filter that cuts by 12 dB:

d = fdesign.parameq('N,Flow,Fhigh,Gref,G0,GBW,Gst',...
       4,.3,.5,0,-12,-10,-1);
 Hd = design(d,'cheby2');
 fvtool(Hd)

Design a 4th order audio lowpass (F0 = 0) shelving filter with cutoff frequency of Fc = 0.25, quality factor Qa =10, and boost gain of G0 = 8 dB:

d = fdesign.parameq('N,F0,Fc,Qa,G0',4,0,0.25,10,8);
Hd = design(d);
fvtool(Hd)

Design 4th-order highpass shelving filters with S=1.5 and S=3:

N=4;
F0 = 1;
Fc = .4; % Cutoff Frequency
G0 = 10;
S = 1.5;
S2=3;
f = fdesign.parameq('N,F0,Fc,S,G0',N,F0,Fc,S,G0);
h1 = design(f);
f.S=3;
h2=design(f);
hfvt=fvtool([h1 h2]);
set(hfvt,'Filters',[h1 h2]);
legend(hfvt,'S=1.5','S=3'); 

Version History

Introduced in R2011a

R2022a: fdesign.parameq will be removed

The fdesign.parameq filter specification object will be removed in a future release. Existing instances of the object continue to run. For new code, use the designParamEQ (Audio Toolbox) function instead.

Update Code

This table shows how the object is typically used and explains how to update the existing code to use the designParamEQ function. The designParamEQ function requires Audio Toolbox™.

Discouraged Usage	Recommended Replacement
Design based on Filter Bandwidth Fs = 48e3; N = 2; Q = 10; G = 9; % 9 dB % Normalized center frequency Wo1 = 2000/(Fs/2); Wo2 = 12000/(Fs/2); % Normalized bandwidth BW1 = Wo1/Q; BW2 = Wo2/Q; PEQ = fdesign.parameq('N,F0,BW,Gref,G0,GBW',N,Wo1,BW1,0,G,4.5); BQ1 = design(PEQ,'SystemObject',true); PEQ.BW = BW2; PEQ.F0 = Wo2; BQ2 = design(PEQ,'SystemObject',true); % Visualize the filters hfvt = fvtool(BQ1,BQ2,'Fs',Fs,'Color','white'); legend(hfvt,'BW1 = 200 Hz; Q = 10','BW2 = 1200 Hz; Q = 10');	Design based on Filter Bandwidth Fs = 48e3; N = 2; Q = 10; G = 9; % 9 dB % Normalized center frequency Wo1 = 2000/(Fs/2); Wo2 = 12000/(Fs/2); % Normalized bandwidth BW1 = Wo1/Q; BW2 = Wo2/Q; [B1,A1] = designParamEQ(N,G,Wo1,BW1); [B2,A2] = designParamEQ(N,G,Wo2,BW2); BQ1 = dsp.BiquadFilter('SOSMatrix',[B1.',[1,A1.']]); BQ2 = dsp.BiquadFilter('SOSMatrix',[B2.',[1,A2.']]); % Visualize the filters hfvt = fvtool(BQ1,BQ2,'Fs',Fs,'Color','white'); legend(hfvt,'BW1 = 200 Hz; Q = 10','BW2 = 1200 Hz; Q = 10');
Design based on Quality factor Fs = 48e3; N = 2; G = 15; % 15 dB % Quality factor Q1 = 0.48; Q2 = 1/sqrt(2); % Normalized center frequency % F0 = 1 designs a highpass filter % F0 can either be 0 or 1 in this configuration F0 = 1; % Cutoff Frequency Fc = 6e3/(Fs/2); PEQ = fdesign.parameq('N,F0,Fc,Qa,G0',N,F0,Fc,Q1,G); BQ1 = design(PEQ,'SystemObject',true); PEQ.Qa = Q2; BQ2 = design(PEQ,'SystemObject',true); % Visualize the filters hfvt = fvtool(BQ1,BQ2,'Fs',Fs,'Color','white'); legend(hfvt,'Q = 0.48','Q = 0.7071');	Design based on Quality factor Fs = 48e3; N = 2; G = 15; % 15 dB % Quality factor Q1 = 0.48; Q2 = 1/sqrt(2); % Normalized center frequency Wo = 6000/(Fs/2); % Normalized bandwidth BW1 = Wo/Q1; BW2 = Wo/Q2; [B1,A1] = designParamEQ(N,G,Wo,BW1); [B2,A2] = designParamEQ(N,G,Wo,BW2); BQ1 = dsp.BiquadFilter('SOSMatrix',[B1.',[1,A1.']]); BQ2 = dsp.BiquadFilter('SOSMatrix',[B2.',[1,A2.']]); % Visualize the filters hfvt = fvtool(BQ1,BQ2,'Fs',Fs,'Color','white'); legend(hfvt,'Q = 0.48','Q = 0.7071');
Low shelf and high shelf filters Fs = 48e3; N = 4; G = 10; % 10 dB % Normalized center frequency Wo1 = 0; % Lowpass filter % Corresponds to Fs/2 (Hz) or pi (rad/sample) Wo2 = 1; % Highpass filter % Bandwidth occurs at 7.4 dB in this case BW = 1000/(Fs/2); PEQ = fdesign.parameq('N,F0,BW,Gref,G0,GBW',N,Wo1,BW,0,G,3); BQ1 = design(PEQ,'SystemObject',true); PEQ.F0 = Wo2; BQ2 = design(PEQ,'SystemObject',true); % Visualize the filters hfvt = fvtool(BQ1,BQ2,'Fs',Fs,'Color','white'); legend(hfvt,'Low Shelf Filter','High Shelf Filter');	Low shelf and high shelf filters Fs = 48e3; N = 4; G = 10; % 10 dB % Normalized center frequency Wo1 = 0; % Lowpass filter % Corresponds to Fs/2 (Hz) or pi (rad/sample) Wo2 = 1; % Highpass filter % Bandwidth occurs at 7.4 dB in this case BW = 1000/(Fs/2); [B1,A1] = designParamEQ(N,G,Wo1,BW); [B2,A2] = designParamEQ(N,G,Wo2,BW); BQ1 = dsp.BiquadFilter('SOSMatrix',[B1.',[ones(2,1),A1.']]); BQ2 = dsp.BiquadFilter('SOSMatrix',[B2.',[ones(2,1),A2.']]); % Visualize the filters hfvt = fvtool(BQ1,BQ2,'Fs',Fs,'Color','white'); legend(hfvt,'Low Shelf Filter','High Shelf Filter');