Ask anyone who's tried to exercise at home in a flat or a shared house, and noise usually comes up before anything else — before price, before features, before how it looks in the room. It makes sense: nobody wants a treadmill that announces itself to the whole building.
A few practical things tend to make more difference than people expect. Where the machine sits matters as much as the machine itself — a firm, level floor transmits far less vibration than a soft or uneven one, and a simple mat underneath can take the edge off both noise and impact. Footwear matters too; a supportive, cushioned shoe absorbs more of the impact than bare feet or thin socks.
Timing helps as well. A short walking session first thing in the morning or during a work break tends to be far less disruptive than one late at night, simply because ambient noise levels are higher during the day.
The other factor worth thinking about before buying is the machine's own footprint — not just its size, but how it's built to be positioned. A treadmill you can push flush against a wall, away from shared floor space, is generally going to feel less intrusive than one sitting in the middle of a room.
None of this guarantees silence. But between placement, footwear and timing, most people find they can fit a walking routine into a shared home without it becoming a source of complaints.