The Language of Ears
The position of the ears is one of the most important indicators of a horses mood and intentions. Ears pricked forward are a sign of alert curiosity and good mood. Ears tucked back are often a sign of relaxation, or even boredom. They may also be a sign that the horse is unwell. The ears pressed flat against the head are a classic sign of bad temper and aggression. It can also signify that the horse is feeling stressed. When the ears flop to either side, it may be a sign of sleepiness or sickness. It is also a typical sign of submission to a more dominant horse.
How Horses Hear
Horses are very sensitive to sound, and can hear high- and low-pitched noises that humans are unable to pick up.
The pinna, or funnel part of the ear, picks up the sound waves and directs them down inside the the head where a network of bones and chambers together with the eardrum transmit and amplify them for special nerves to pick up. These nerves in turn transmit these messages to the brain, which translates the sounds into meaning if they are familiar, or alerts the horse to something strange in its environment if they are not.
A horse does not automatically panic at unfamiliar sound; it will pay attention to it and remember it. If something happens at the same time as the sound, it will, in future, associate the happening with that sound, and this is important part of training and learning.
Horses' hearing is sharper than that of humans; they can hear things like other horses calling, car engines (which they can tell from each other) and doors opening, before a person can pick them up and from much farther away. Horses that are boarded out, for example, soon come to recognize their owners' car engines and associate the noise with the appearance with that particular person. They will often pick up on a sound long before the staff in the stable.
Horses are extremely sensitive to the nature of a sound and it's volume. There is never any need to shout at a horse unless it is a very dominate animal either attacking or really pushing it's weight around, in which case volume can help get the better of it. Tone of voice is usually more effective than volume; a cross growl when a horse is doing wrong, and an up-and-down, pleased tone for praise.
Screaming, and screeching often frighten horses, whereas soft momotones calm them down. However, some sounds which might be thought to frighten them, such as blasting in a quary or police sirens, do not always do so.
Horses are as agitated by constant, raucous sound as humans are. In racing stables, for instance, the best trainers insist on a quiet period during the afternoon after morning work, grooming and the midday feed, so that the horses can lie down and rest or have a sleep.
Some horses prefer a busy atmosphere where they can see and hear what is going on around them, and others like peace and quiet. It is important to watch your horse and try to tell by its behavior and expression which category it falls into. If it seems slightly (or very) tense, its ears flicking around a lot, not resting much during the day, it could be that there is to much noise going on for its liking.
The best thing a person could do for their horse is; getting to really know your horse, watch it's every mood, pay attention to the subtle movements in its ears, and really listen to your horse. It will let you know how it's feeling, if you just listen.