#!/usr/bin/perl -w

# Rename this to fm-28.pl to get it to run on Windows (after
# installing Perl)

$rate= 44100;
$mf= 28/$rate;		# Modulation frequency

$lfmid= 207/$rate;	# Carrier centre
$lfwid= 100/$rate;	# Carrier width
$lfph= 0;		# Phase for frequency 
$lph= 0;		# Phase for signal

$rfmid= 193/$rate;	# Carrier centre
$rfwid= 100/$rate;	# Carrier width
$rfph= 0;		# Phase for frequency 
$rph= 0;		# Phase for signal

$twopi= 4 * atan2(1,0);

sub u32 { return pack "V", $_[0]; }

die unless open OUT, ">out.wav";

$cnt= $rate * 10;
$len= $cnt * 4;
print OUT "RIFF" . u32($len + 36) . "WAVE" . "fmt " . u32(16) . u32(0x00020001) .
    u32(44100) . u32(44100*4) . u32(0x0004 + 0x10000*(4*4)) . "data" . u32($len);

while ($cnt-- > 0) {
    $lfph += $mf;
    $lph += $lfmid + $lfwid * sin($lfph * $twopi);
    $ll= sin($lph * $twopi);
    $rfph += $mf;
    $rph += $rfmid + $rfwid * sin($rfph * $twopi);
    $rr= sin($rph * $twopi);
    
    print OUT pack("vv", $ll * 16834, $rr * 16384);
}
    
close OUT;