Download speed limit met php

[code]
<?php
$file = "test.mp3";
$speed = 500.0;

 
if(file_exists($file) && is_file($file)) {
header("Cache-control: private");
header("Content-Type: application/octet-stream"); 
header("Content-Length: ".filesize($file));
header("Content-Disposition: filename=$file"); 
flush();
$fd = fopen($file, "r");

	while(!feof($fd)) {
	
	echo fread($fd, round($speed*1024));
	flush();
	sleep(1);
   }
   
fclose ($fd);
}
?>
[/code]