Description

A notch filter whose transfer functions are the complements of the reson opcode.

Syntax

kres aresonk ksig, kcf, kbw [, iscl] [, iskip]

Initialization

iscl (optional, default=0) -- coded scaling factor for resonators. A value of 1 signifies a peak response factor of 1, i.e. all frequencies other than kcf are attenuated in accordance with the (normalized) response curve. A value of 2 raises the response factor so that its overall RMS value equals 1. (This intended equalization of input and output power assumes all frequencies are physically present; hence it is most applicable to white noise.) A zero value signifies no scaling of the signal, leaving that to some later adjustment (see balance). The default value is 0.

iskip (optional, default=0) -- initial disposition of internal data space. Since filtering incorporates a feedback loop of previous output, the initial status of the storage space used is significant. A zero value will clear the space; a non-zero value will allow previous information to remain. The default value is 0.

Performance

kres -- the output signal at control-rate.

ksig -- the input signal at control-rate.

kcf -- the center frequency of the filter, or frequency position of the peak response.

kbw -- bandwidth of the filter (the Hz difference between the upper and lower half-power points).

aresonk is a filter whose transfer functions is the complement of resonk. Thus aresonk is a notch filter whose transfer functions represents the “filtered out” aspects of their complements. However, power scaling is not normalized in aresonk but remains the true complement of the corresponding unit.

Examples

Here is an example of the aresonk opcode. It uses the file aresonk.csd.

<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac     ;;;RT audio out
;-iadc    ;;;uncomment -iadc if RT audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o aresonk.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>
sr = 44100
ksmps = 32
nchnls = 2
0dbfs = 1

gisin ftgen 0, 0, 2^10, 10, 1

instr 1

ksig	randomh	400, 1800, 150
aout	poscil	.2, 1000+ksig, gisin
	outs	aout, aout
endin

instr 2

ksig	randomh	400, 1800, 150
kbw	line	1, p3, 600	; vary bandwith
ksig	aresonk	ksig, 800, kbw
aout	poscil	.2, 1000+ksig, gisin
	outs	aout, aout
endin

</CsInstruments>
<CsScore>
i 1 0 5
i 2 5.5 5
e
</CsScore>
</CsoundSynthesizer>

See also

Standard Filters: Control signal filters