This polished brass bell looks like any other small bell used for summoning staff, producing a small 'ting' with each press of the plunger.

However, hitting the bell with a medium amount of force makes the bell sound like a large church bell, tolling loudly and can be heard by everyone in a 300' radius. This sound will cause plates to rattle, loose objects to move, dust to fall from rafters etc. Other than the user, a DC12 CON check must be made to avoid being deafened for 1d4 minutes.

Finally, if more than 10 lbs of pressure is used to ring the bell by an attuned user, this noise increases in decibels and acts as a Thunderwave spell:

A wave of thunderous force sweeps out from you. Each creature in a 15-foot cube originating from you must make a Constitution saving throw. On a failed save, a creature takes 2d8 thunder damage and is pushed 10 feet away from you. On a successful save, the creature takes half as much damage and isn't pushed.

Everyone, including the user,  must make a DC15 CON check to avoid being deafened for 2d4 minutes. Passing the check halves the time.

In addition, unsecured objects that are completely within the area of effect are automatically pushed 10 feet away from you by the spell's effect, and the spell emits a thunderous boom audible out to 300 feet.

Notes: Deafened, To attune, the Bell and it's owner need to spend 24 hours in a retail environment, such as a shop or a bar etc.