f <- 16000
a <- synth(d=1,f=f, cf=2000, am=c(50,10), shape="sine")
b <- synth(d=1,f=f, cf=2000, am=c(25,30), shape="tria")
layout(matrix(c(1,2,3,3),byrow=TRUE,nc=2))
env(a,f=f,colwave="red",title="sound 'a'")
env(b,f=f,colwave="blue",title="sound 'b'")
diffenv(a,b,f=f,plot=TRUE,main="surface difference between 'a' and 'b'")