#  Data is weighted by sine squared inside a mute zone.
#  The weight is zero when	t <       x * slope0
#  The weight is one  when      t >  tp + x * slopep
#  Suggested defaults: slopep = slope0= 1./1.45 sec/km;  tp=.150 sec
#
subroutine mutter( tp, slope0,slopep, dt,dx, t0,x0, data,nt,nx)
integer it,ix,                                           nt,nx
real t,x, wt,      tp, slope0,slopep, dt,dx, t0,x0, data(nt,nx)
do ix=1,nx {	x= x0+(ix-1)*dx;	x = abs( x)
do it=1,nt {	t= t0+(it-1)*dt;
	if     ( t <      x * slope0)  	wt = 0
	else if( t > tp + x * slopep)	wt = 1.
	else				wt = sin(
		0.5 * 3.14159265 * (t-x*slope0)/(tp+x*(slopep-slope0))) ** 2
	data(it,ix) = data(it,ix) * wt
	}}
return; end