To go through level 40 on 100 floors, what you need to do is mute the volume or turn it down completely. The elevator door will then open when it is silent and you will b able to pass that level. The site http://100floorsanswers.com/ should help you with other levels if you get stuck.
Turn the volume all the way down. If you're playing on a mobile device, press the volume button down all the way. If you're playing on an iPod or similar device, I think you just turn down the volume. Screenshots: http://www.freeappgg.com/floor-40.html