harmo.pl

#!/usr/bin/perl
# Oona Räisänen 2014
use warnings;

$fs = 48000;
$f  = 200;
$pi = 3.141592653589793238;

open(U,"|sox -t .raw -c 1 -r $fs -b 16 -e signed - sines.wav");

$p = 0;
for $step (1,1,1,1..120,120,120,120,120,120,120) {
  $n = 0;
  $steplen = 0.5*$fs * (1-$step/131);

  while ($n < $steplen) {

    $a = 0;
    $a += harmo($_, $p) for (1..$step-1);
    if ($n < 400 && ($prevstep // 0) != $step) {
      $a += harmo($step, $p) * ($n/400);
    } else {
      $a += harmo($step, $p);
    }

    $n++;
    $p++;

    print U pack("s",$a);
  }
  $prevstep = $step;
}

close(U);

sub harmo {
  ($ord,$ph) = @_;
  my $ampf = .5 * -(2/($ord*$pi))* (-1)**$ord;
  $ampf * 32000 * sin ( $ph / $fs * ($ord*$f) * 2 * $pi);
}