It depends a lot on what your morals are. If you are that close to the neighbors and you witness these things, then you can register a complaint with the local police dept. They will investigate. Most times they already have had other complaints. In a day and age where no one wants to get involved you have to ask yourself something. When you go to sleep do you wonder what is happening over there and if you don't call will someone be injured or worse? Also, if you do call, are you wondering if it will come back on you? You can tell the officer you wish to remain anonymous. And also inform them as to how long this is going on. Domestic violence does not go away by itself. We can be a part of the problem by doing nothing or part of the solution by bringing those to justice. No one should be beat. And if this person has no way out, you may be that way. Another way to think about it is this: If that were my sister and her neighbors did nothing to save her, how would I feel? A lot to think about. I would go with my conscious.
Yes, you must definitely report this to the police. It is not uncommon for this type thing to end in someone being beaten to death by a spouse or life partner. If it is a child that is being beaten/tortured, then you have even more of a moral obligation to protect that child. Do not delay, please. If you are fearful that you are wrong in your assumption; it is better for you to be wrong and report it than for you to be right and not report it. Someone could die next door. Do you want to live the rest of your life with that on your conscience...could you sleep at night know that you let it go on until someone was killed or permanently injured??? Please, report it today!!
If you believe that there is domestic violence then you should definitely report it.
If you are absolutely certain thats what's going on I'd say yes