Likely the act of splitting wood already has your neighbors sensitive. I doubt quieting it down a bit will help much.
I'd actually go to town court about this if necessary. We have those ordinances in the town where the family home is in NY. But the ordinances deal with nosie, and are in place because of landscaping businesses, primarily. You cannot operate a leaf blower or lawn mower etc before 7 AM, which is reasonable. There is absolutely no regulation dealing with a private homeowner using hand tools, or snowblowers even.
If you are doing work for yourself on your property and using hand tools, it is reasonable for you to occcasionally be working in your yard evenings, even making a bit of noise with hand tools, until about 7 PM. After that, it's best to restrict yard activities to quiet ones...raking, cleaning, hand gardening, etc. On the other hand, I could see every single night, especially from a new neighbor, of whack, whack, whack getting old soon. People are usually pretty resistant to change.
The object of such rules is always to prevent offensive noise at unreasonable time. For instance, loud music outside is not allowed after 10 PM. Dogs cannot be permitted to bark continuously for over ten minutes. These are not unreasonable in towns where homes are side to side and back to back on 1/10 to 1/4 acre lots. Everythin g you do that is noisy impacts others.
If you are splitting wood at night after work and after dinner, you may be disturbing people who are trying to get their kids to do homework or go to bed. There are kids who will be distracted by such activities as a neighbor splitting wood. Or you may be disturbing folks who are just tired and have been listening to noise all day and want some peace and quiet.
If you are splitting after dinner, and for some reason MUST do some splitting after dinner, try splitting as soon as you get home, and eating later. Or, better yet, split on the weekend and stack during the week. Stacking needs to be done, is good exercise, and is quiet. Furthermore, any neighbor looking out and seeing you clean up in the evening will likely be pleased, as opposed to irritated. If not many people heat with wood near you, the sudden appearance of large amounts of wood dropped off in the front or side yard of a new neighbor may have folks worried about what your yard is going to like all the time, and its impact on their property value. Make it clear that the actual wood processing is primarily for a few months, and as the wood is processed it will be stacked in neat, attractive stacks, placed as considerately as you can place them.
In a suburban area, having logs dropped off and processing them in a front yard is almost akin to running a business, in its impact on neighbors, compared to the impact of most people's activities.
Basically, try to put yourself in your neighbor's shoes, and then deal with him/her the way you'd want them to deal with you.
Maybe invite them over to watch a basketball or baseball game on the TV with you, over a buffet meal. If it's chilly, have a nice little fire going. Try talking tree species between innings. Explain about the need for dry wood in order to burn cleanly and not pollute the air in the neighborhood, hence your anxiety to get your wood split and stacked before summer, so it has time to dry properly. Make them want you to get it done quickly.
You really should be able to get the wood split weekends if necessary. Surely there is no ordinance against homeowner yard work Saturdays and Sunday afternoons?
I'd be thinking more along these lines, than trying to find a tool that makes splitting a little quieter.
I bet its the entire activity that is disturbing (as in concerning) people, not just the noise.
{It would not bother me to have a neighbor splitting wood, but i grew up with my Dad working every minute he was home, at one thing or another. On the other hand, I wouldn't be terribly happy about truckloads of wood regularly being dropped off next door if I lived on a suburban lot...unless I knew it would only happen a few times a year. }