Definition: Problems with the respiratory system, especially the larynx can cause a horse to make a roaring noise, especially when cantering or galloping. Roaring may be annoying but relativly harmless in a pleasure horse if the cause is known and taken care of. Some horses make a snorting noise with each stride of the canter or lope. However, sudden roaring, or roaring in a performance horse needs veterinary attention. Have your veterinarian check your horse if it roars to be sure that no medical treatment is required.