Koetting is dangerously unreliable and as someone with experience in electroencephalography, take it from me that syncing your brain to this or that frequency has nothing to do with interacting with spirits. In fact, you are much more likely to put yourself into a confused state and become more receptive to any unwanted psychic influence, and / or underlying psychological illnesses. If you nonetheless want to ignore this advice and try anyways, find yourself a qualified neurotherapist who might actually be able to help you entrain your brainwaves in order to help address your problems... Unlike Koetting.
Now, if you want better advice, please provide us with more specific information about your problems, why you believe a spirit to be their cause, and what you have already tried.