All refrigerators “work” by a process of “pumping heat” from the inside of the box (including the freezer) to a compressor / condenser outside of the box which gives off heat in the condenser coils (which can be on the bottom of the box, as @john65pennington suggests, or sometimes in a vertical array on the back – though this isn’t so common on modern appliances). When the compressor is operating (because the sensors inside the freezer or refrigerator compartments sense a need to remove some excess heat), then it makes a sort of humming noise, as any functional pump will. On a modern appliance you won’t hear that unless you’re close to it, or unless the dwelling is absolutely silent otherwise and you have good hearing.
On the other hand, as others have also suggested, the modern machines with ice-making capability make more noise: the water runs intermittently as new layers of ice are made in the ice-building chamber / tray, and the crushers work if you have chosen (and have an option for) crushed ice dispensing, and the entire tray makes and ejects ice until the sensor that says “stop making ice; the tray is full” signals the process to halt until the ice is consumed. The ice making, ejecting and dispensing process is pretty loud – and until enough ice is made and stored in the freezer, it can be an ongoing (though not “continuous”) process.
So if you’ve just purchased the machine, and especially if you’ve recently loaded it with hot / warm / room-temperature perishables, then the machine will work to attain its operating temperature. That process normally won’t take more than a couple of hours, even from a standing (room temperature) start. The ice-making process can take longer, especially if you’re using the ice as it is created.