I would suggest taking a close look at NH RSA 644:2, Disorderly Conduct, and specifically Section III A as it applies to loud or unreasonable noise from a private place which can be heard in another private place, etc. Admittedly the average sensibility standard is subjective but what you describe certainly seems to fit. Since this is a State criminal statute you avoid the issues with the Town Ordinance. If I had this issue I would have a form prepared addressed to the offender stating the date, time, place and nature of the conduct and a request to immediately cease, perhaps pointing out that if the conduct continues, then the conduct becomes a misdemeanor rather than just a violation. See Section VI. Perhaps also give them a copy of the Statute.
http://www.gencourt.state.nh.us/rsa/.../644/644-2.htm