It used to be that stuffed animals came pre-made with sound buttons only. Now small sound buttons can be purchased separately and added to stuffed animals you bought or made at toy-building workshops. It is best to add sound buttons to the paws of animals as there are usually seams that can be easily undone and re-sewn as opposed to cutting out a portion of the toy's back or side. A child will only have to lightly squeeze the animal's paw to produce a sound.
Purchase a press sound button based on the size and type of sound device you want. Some devices only play music while others only allow you to record your voice or a particular sound. Some do both. Small round buttons are optimal for small and medium-sized stuffed animals 1.
Make a cut along the seam of your plush animal's paws, either foot or hand depending on preference. Insert the button in the paw. Place the button more towards the front of the paw so it does not get lost in the toy's stuffing, which can make the device less audible.
Perform a test run on the toy before sewing the paw back up. If the sound device is audible, sew the paw seams to enclose the device. If not, re-arrange the device and do more test runs until you are satisfied with how well you can hear the sound.
Tips
Use sound devices in handmade plush toys. Choose stuffed animals with soft plush filling when using sound buttons. Some animals are filled with bean bag-type stuffing, which is more likely to interfere with the device.