My downstairs neighbor complained to management that my walking was too loud. So I bought a treadmill.

Let me be upfront: I am a normal weight adult who wears socks inside and does not stomp. I have lived in this apartment for two and a half years without a single complaint from anyone. About four months ago a new tenant moved into the unit below mine. Within three weeks she had filed two noise complaints with building management saying my footsteps were disruptive during the day. Management came up, walked around my apartment themselves, and told me there was nothing unusual about the sound and that the building was older and sound traveled. They said they'd note it but there was nothing to address. The neighbor then started knocking on my ceiling, which is her floor, at random intervals during the day whenever I moved between rooms. Not late at night. Like 2pm on a tuesday. I started keeping a log with timestamps. Six weeks ago I decided to start working out at home instead of going to the gym, partly for convenience and partly, I will be honest, because I had already decided I was done modifying my behavior for someone whose complaint had been dismissed by management. I bought a treadmill. It is on a thick rubber mat. I use it for 40 minutes every day at 6pm, which is well within quiet hours. The vibration from a treadmill on a rubber mat is actually less impactful than walking because the motion is absorbed. I know this because I looked it up. She filed another complaint two weeks ago. Management reviewed my log, noted the complaint had been filed during documented treadmill hours, and reminded her that exercise equipment is permitted under the lease. I have not changed my 6pm schedule.