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

## Description

Find the frequency response of a digital filter

## Usage

 ```1 2``` ```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 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

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17``` ```## 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 May 1, 2019, 6:26 p.m.