A simple way to introduce everyday noises and unfamiliar objects so they register as background, not threats.
Vacuum cleaners, traffic, thunderstorms, and doorbells can become triggers for fearful or reactive adult dogs. Calm, manageable introductions during puppyhood can help build familiarity, but one exposure does not determine the whole outcome.
Introduce a new sound or object at low intensity or from far away — the vacuum off and visible before it's on, traffic from across a quiet street before a busy one. Watch your puppy's body language rather than a fixed distance; relaxed and curious is the target. If the vacuum already causes hiding, barking or chasing, use Puppy Scared of the Vacuum to separate its sound, movement and approach.
Treats, calm praise, or a favorite toy alongside the new thing build a positive association faster than exposure alone. The goal is for your puppy to associate the trigger with good things happening, not just to "get used to it."
If your puppy backs away, that's useful information, not something to push through. Increase distance, lower the intensity, and try again — moving too fast is the most common way well-meaning exposure backfires.
Vacuum, hairdryer, doorbell, umbrella opening, wheeled suitcases, hats, uniforms, stairs, different flooring — a little variety across a few weeks covers far more ground than repeating the same one thing. There's no need to rush through the whole list at once.