Their mum Jenny Packham, who is an audiologist, said it was a fun activity for her daughters to take part in but she also wanted to support the charity because of her line of work.
Everyone who decorated a T-shirt made a gold coin donation and the proceeds would go to The Hearing House and the Southern Cochlear Implant Programme.
Rotorua Museum events and engagement co-ordinator Tori Williams said it was the first time the museum had partnered with Loud Shirt Day, and the day had been a success.
"Today was a trial but it's been successful so I hope to continue with something similar next year," she said.
Williams had seen a wide range of different creations from the children including tie-dying and painting castles and dragons on T-shirts.
Loud Shirt Day is on Friday. For more information or to donate to this charity go to www.loudshirtdaynz.org
