I know a couple who renovated a great old house not too long ago and committed what I consider an egregious error: They removed all of the solid wood interior doors and installed $30 hollow-core numbers instead. I cringed when I found out. What’s the big deal, they wanted to know, so I explained it to them this way: I told them that what they did was the equivalent of taking out their wood floors and putting in laminate. Granted, the old doors needed some repairs—scraping, patching, sanding, painting—but with a little elbow grease, they would have looked like gems. Hollow-core doors are affordable, but they feel like crap, look like crap, and are useless in blocking out noise. Which is why we recommend solid-core doors made from wood, medium density fiberboard, engineered wood, or some other composite material. Doors made from these materials will block sound, feel substantial in your hands, and will have a nice crisp appearance. You can buy them at The Home Depot or Lowe’s, or 84 Lumber; you can also get some nice ones from Simpson Door Co., Tru-Stile Doors, Signamark, and Jeld-Wen. If you really want to be adventurous, stop by your salvage yard; they always have solid wood doors that you can buy for cheap.