Is ‘preload=”none”‘ a valid parameter in the [audio] shortcode in WordPress 3.6?

I looked at the wp_audio_shortcode function in wp-includes/media.php of the release version of WordPress 3.6. The preload parameter is a valid attribute of the shortcode. However, the default is ‘none’, so in my case it is not needed.

From WordPress 3.6 (release), wp-includes/media.php, function wp_audio_shortcode:

$default_types = wp_get_audio_extensions();
$defaults_atts = array(
    'src'      => '',
    'loop'     => '',
    'autoplay' => '',
    'preload'  => 'none'
);
foreach ( $default_types as $type )
    $defaults_atts[$type] = '';

$atts = shortcode_atts( $defaults_atts, $attr, 'audio' );

So the answer is, yes, it is a valid parameter in the shortcode, but the default value is ‘none’, so in this case it is not needed.