The Redstone Doorbell is placed on the wall near the door of the house and it gives different sounds from different blocks.
In order to make a Redstone Doorbell, you first need to make a small house exterior like structure. Make spruce wood walls and roof of a house and use an iron door at the front as shown in the image below.
Make another spruce wood wall on the right side and use a redstone lamp in this wall. Add a birch button on the lamp and place four wool blocks at the back side of the lamp. Add redstone dust on the first one.
Add two note blocks and one redstone repeater as shown in the image below. Set the repeater to maximum delay.
Press the birch button on the lamp to ring the bell.
But it doesn’t sound well. You can try gold blocks instead of the wool blocks as different blocks have different sounds.