#----------------------------------------------------- 
#  Use of seewave to produce a gated sinusoidal wave
#
#  GdA 21/5/2016
#-----------------------------------------------------

library(seewave)

sinusoidal <- function(nu=440, t.max=1/nu, sampling=44100) {
   sin(2*pi*nu*seq(0, t.max, length.out=t.max*sampling))
}

nu       <- 440     # Hz
t.max    <-  10     # seconds
sampling <- 192000  # Hz (samples/s)  (41000,  96000, 192000)
Ampl     <-  0.2    # relative amplitude

n.off <- 10  # nr of periods OFF
n.on  <- 10  # nr of periods oscillating (ON)

wave.sin <- Ampl*sinusoidal(nu, sampling=sampling)  # 1 period
npw      <- length(wave.sin)                        # nr of points 
wave.off <- rep(0, npw)                             # zero (OFF) for 1T 

T <- 1/nu                   # period
n.periods <- t.max/T        # nr of periods in t.max
n.cycles <-  t.max / ( (n.off + n.on) * T)   # nr of OFF/ON periods

# build the gated wave 
wave <- rep( c( rep(wave.off, n.off),
                rep(wave.sin[1:(npw-1)], n.on)      # (*)  
              ), n.cycles)  
                           # (*) overlapping zero's are removed [ "1:(npw-1)" ]

# uncomment to inspect the resulting wave 
# plot(wave[1:20000], ty='l') 

# save wave as wav file
savewav(wave, f=sampling)

# play it (or comment the line to play from console)
system("play wave.wav")