Actually the correct lyrics to this intro are:

I'm sure it's getting darker
Don't make a sound
Don't make a sound

You hold the answer deep within your own mind
Death in it's most hideous form

Someone else on here pointed this out.

You can hear the "I'm sure it's getting darker, Don't make a sound, Don't make a sound" around 0:00 through 0:10. It's clearer around 0:05 to 0:07. It's very faint and you can only hear "Darker" and Don't make a sound, Don't make a sound" if you aren't listening closely. This may be different for some people but, if you listen to this over and over again, or see this when after you have listened to this intro, it's possible you won't hear it. So wait about an hour or two and then listen it again.