phonTools (version 0.2-2.0)

findformants: Find Formants

Description

Find formants given a sound or set of LPC coefficients.

Usage

findformants (sound, fs = 10000, coeffs = NULL, maxbw = 600, 
minformant = 200, verify = TRUE, showbws = FALSE, 
showrejected = TRUE)

Arguments

sound

A numeric vector representing a waveform, or a 'sound' object created with the loadsound() or makesound() functions.

fs

The sampling frequency of the sound. If a 'sound' object is passed this does not need to be specified.

coeffs

If a number is given, this many coefficients are used in the analysis. Alternatively, the LPC (AR filter) coefficients may be passed to the function directly using this parameter. For good results, two coefficients are required for each formants plus 2 or

maxbw

The maximum bandwidth for accepted formants.

minformant

Formants below this frequency are rejected.

verify

If TRUE, a plot is created which allows the user to visually inspect the process.

showbws

If TRUE, formant bandwidths are indicated on the plot.

showrejected

If TRUE, rejected formant locations are indicated.

Value

• A dataframe with the following elements is returned:
• frequency
  The frequencies of formants, in ascending order.
• bandwidth
  The corresponding formant bandwidth.

Details

Formant frequencies are found analytically using the formulas provided in Snell (1993). If Verify = TRUE, the estimated frequency response, formant locations, and a pole-zero plot of the estimated filter are presented. Accepted formants are presented in 5 colors (which are reused if there are more than 5 formants), while rejected formants are presented in black.

References

Snell, R.(1993). "Formant location from LPC analysis data", IEEE Transactions on Speech and Audio Processing, 1(2), pp. 129-134.

Examples

## make a synthetic vowel with a known set of formant frequencies
## and bandwidths
sound = vowelsynth (ffs = c(500,1500,2500,3500,4500),
                    fbw = c(30, 90, 150, 210, 270), f0 = 100)

## compare different plotting options					
findformants (sound)
#findformants (sound, showrejected = FALSE)
#findformants (sound, showbws = TRUE)