How do Horse 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 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 message 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 an 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 an important part of training and learning.
Horses’ hearing is sharper than that of humans; they can hear things like other hoses calling, car engines (which they can tell from each other) and doors opening, before a person can pick them up and from much further away. Horses kept at livery, for example, soon come to recognize their owners’ car engines and associate the noise with the appearance of that particular person. they will often pick up the sound and react to it long before the staff in the yard.
Horses are extremely sensitive to the nature of a sound and its volume. There is never any need to shout at a horse unless it is a very dominant animal either attacking or really pushing its 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 the horse is doing wrong, and an up-and-down, pleased tone for praise.
Screaming and screeching often frighten horses, whereas soft monotones calm them down. However, some sounds shich might be thought to frighten them, such as blasting in a quarry or police sirens, do not always do so.
Horses are as agitated by constant, raucaous sound as human are. In 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 behaviour and expression whch 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 too much noise going on for its liking.
MUSIC
Experiments carried out with mares at the Irish National Stud some years ago showed that horses like 
music, but are selective in their tastes. Most horses like calming and cheerful instrumental music and are agitated by heavy, lound unmelodious music such as rock. Vocal music is also not as welcome to them as instrumental music.
Dressage performed to music is now popular in many countries and the horses really seem to enjoy it. They appear perky, majestic, calm or energetic according to the music chosen for their routine. Like circus horses, they often associate the music with particular movements.
Remember that your horse is a prisoner in its box. You may enjoy having a radio playing while you work, but see whether your horse enjoys it as much as you do. Never leave a radio on all the time as it can really get on a horse’s nerves, andbe selective about the programmes you tune in to, and the type of music played. The horse has to rely on you for both its entertainment and its peace and quiet.
LOVE CALLING!
Another experiment done at the Irish National Stud was that of playing the sound of a stallion calling to an in season mare to study the effect this had on the brood mares stabled in a particular barn. It was found that those in season and ready to mate showed signs of being amenable to the stallion even though he was not present, and those not in season came into season after a very few days of the sound being played to them intermittently.
THE LANGUAGE OF EARS
The position of the ears is one of the most important indicators of a horse’ mood and intentions. Ears pricked forward are a sign of alert curiosity and good mood. Ears pricked forward are a 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 thatthe horse if feeling stressed. When the ears flop to either side, it may be a sign of sleepiness or sickness. It os also a typical sign of submission to a more dominant horse.
The position of the horse’ ears on the sides of its head enables it to hear almost all around it. Each ear can pick up sounds to the front and side learning a gap immediately begind it which it can cover with a small turn of its head.