spray closed cell foam is the most effective, but costly. of course you
dont need much but its a small job.

it deadens sound 2 ways, makes it harder to transmit, and prevents air
passage which ultimately allows sound to pass.

try running a fan or other white noise generator at night to mask the
noise.

new fridges are much more energy efficent but the tradeoff is noise

Since its new you might try living with it for a few days you will
eventually adjust.....

just like to the sound of AC or furnace running or occasional street
noise, your brain says thats normal let him sleep

yur fridge is new so your brain says wake him might be hazardous

over time everything will settle out