soundgen (version 1.7.0)

filterMS: Filter modulation spectrum

Description

Filters a modulation spectrum by removing a certain range of amplitude modulation (AM) and frequency modulation (FM) frequencies. Conditions can be specified either separately for AM and FM with amCond = ..., fmCond = ..., implying an OR combination of conditions, or jointly on AM and FM with jointCond. jointCond is more general, but using amCond/fmCond is ~100 times faster.

Usage

filterMS(
  ms,
  amCond = NULL,
  fmCond = NULL,
  jointCond = NULL,
  action = c("remove", "preserve")[1],
  plot = TRUE
)

Arguments

ms

a modulation spectrum as returned by modulationSpectrum - a matrix of real or complex values, AM in columns, FM in rows

amCond, fmCond

character strings with valid conditions on amplitude and frequency modulation (see examples)

jointCond

character string with a valid joint condition amplitude and frequency modulation

action

should the defined AM-FM region be removed ('remove') or preserved, while everything else is removed ('preserve')?

plot

if TRUE, plots the filtered modulation spectrum

Value

Returns the filtered modulation spectrum - a matrix of the original dimensions, real or complex.

Examples

# NOT RUN {
ms = modulationSpectrum(soundgen(), samplingRate = 16000,
                        returnComplex = TRUE)$complex
# Remove all AM over 25 Hz
ms_filt = filterMS(ms, amCond = 'abs(am) > 25')

# amCond and fmCond are OR-conditions
filterMS(ms, amCond = 'abs(am) > 15', fmCond = 'abs(fm) > 5', action = 'remove')
filterMS(ms, amCond = 'abs(am) > 15', fmCond = 'abs(fm) > 5', action = 'preserve')
filterMS(ms, amCond = 'abs(am) > 10 & abs(am) < 25', action = 'remove')

# jointCond is an AND-condition
filterMS(ms, jointCond = 'am * fm < 5', action = 'remove')
filterMS(ms, jointCond = 'am^2 + (fm*3)^2 < 200', action = 'preserve')

# So:
filterMS(ms, jointCond = 'abs(am) > 5 | abs(fm) < 5')  # slow but general
# ...is the same as:
filterMS(ms, amCond = 'abs(am) > 5', fmCond = 'abs(fm) < 5')  # fast
# }