# freqresponse: Frequency Response In phonTools: Tools for Phonetic and Acoustic Analyses

 freqresponse R Documentation

## Frequency Response

### Description

Find the frequency response of a digital filter

### Usage

``````freqresponse (b, a, fs = 0, add = FALSE, show = TRUE,
steps = 1000,...)
``````

### Arguments

 `b` The moving-average (MA), numerator coefficients of the filter. `a` The autoregressive (AR), denominator coefficients of the filter. Please note that the leading 1 at a[0] is not assumed. `fs` The sampling frequency of the sound. If this is not given calculations are presented as if fs = 1. `add` If TRUE, the frequency response plot is added to an existing plot. `show` If TRUE, the frequency response of the estimated filter is plotted. `steps` The number of steps between zero and the Nyquist frequency. `...` Additional arguments are passed to internal plotting functions.

### Details

This function plots (and optionally returns) the frequency response for the digital filter whose transfer function is determined by the numerator and denominator filter coefficients given in b and a.

### Value

A dataframe with two columns (frequency and response) that can be used to redraw the frequency response if required. The 'response' value corresponds to dB. magnitude below peak.

### Author(s)

Santiago Barreda <sbarreda@ucdavis.edu>

### References

Lyons, R. G. (2004). Understanding Digital Signal Processing (2nd ed.). Prentice Hall.

### Examples

``````
## make a synthetic vowel with a known set of formant frequencies
#sound = vowelsynth (ffs = c(500,1500,2500,3500,4500),
#fbw = c(30, 80, 150, 200, 220),f0 = 100, dur = 100)

#plot (sound)

## let the LPC function estimate the filter used to generate the vowel
#coeffs = lpc (sound, show = FALSE)

## compare frequency response of estimated filter to vowel spectrum
#spectralslice (sound, col = 4, preemphasisf = 50)
#freqresponse (1, coeffs, add = TRUE, fs = 10000)

## generate a sinc function
#filt = sinc (seq (-15,15,1/2), normalized = TRUE)
## treat it as a low-pass FIR filter and inspect its frequency response
#freqresponse (filt, 1)

``````

phonTools documentation built on Nov. 21, 2023, 1:07 a.m.