$re = '/\r?\n[^\S\r\n]*[([].+[)\]](?:\r?\n(?![^\S\r\n]*[\[\]()]).*)*\r?\n[^\S\r\n]*[\{(].+\n/m';
$str = 'speaker1: hello
speaker2: hello (clears throat), let me show you something Ted Cruz said last week
(begin audio clip)
Ted Cruz (R-TX): My dad did not shoot JFK, why do people keep saying that?
(end audio clip)
speaker1: now isn\'t that interesting';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php