If you suspect one of your neighbors is being abused, call the police and report it. Don't wait, don't hesitate. Some people call the police because McDonald's screwed up their order. Call the police.
Talk to your neighbors before you call the cops on them!!!!
If you see someone get physically abused then sure, you're witnessing a crime in progress, call the cops. If you're not then don't. It's wildly inappropriate to call the cops on a hunch.
If you think a neighbor is being abused but are not sure then just be their friend and communicate with them (you're neighbors, it's reasonable for you to have each other's phone numbers and email addresses) until you can discern whether or not you are correct. Cops are good at arresting people. They are not good at mediating. If they get called to a DV situation where they can't arrest someone they have a lot of potential to make things worse.
This "wait and see" approach gets people killed.
Personally, I'd far rather be investigated for something I didn't do than have someone else die because a third party didn't act on their suspicions.
Hunches can be wrong, but they come from somewhere, and they're often right.
Furthermore, abusers are good at getting their victims to never tell anyone about what happens, and often at hiding or destroying evidence, too.