Horses have a communication ability just like humans even though it is not written. Not only do horses communicate by sound but also by body language and through their senses. They convey moods and information. On this page I will address horse vocalization. I have no agenda here, nor is this based on science--only my experience and observation with our equine friends.
Whinny or Neigh - A whinny or a neigh often denotes a greeting or an affirmation of location. It is the longest of the horse sounds. The pitch can be from low to high depending of the intensity of the communication. It can be heard as far as 3/4 of a mile away. A neigh or whinny is often heard when a horse is happy to see someone or something, is used as a gentle communication with a foal, is used as a location technique such as finding the herd if separated from the herd or perhaps a mare separated from her foal. The neigh is not fear induced but rather a request for information. Usually the ears are pricked forward, the neck held high, and the tail slightly lifted.
Horse Neighing Sound
Nicker - The nicker is a low pitched guttural sound. I equate it with happiness. It is often heard at feeding time, as a greeting of positive engagement and companionship-- moments of tenderness. Also, stallions will give really quiet nickers to their mares in courtship. Mares will give sweet low pitched guttural nickers to their foals. They will also call to their foals with a nicker. This is thought to be an imprinted behavior with offspring.
Snort - The horse usually holds his head high while exhaling through the nose with his mouth shut. The strong exhale creates a vibration or flutter sound in the nostrils. The snort lasts about 1 second. The snort can be heard up to 30 feet away.
Horse Snorting Sound
Squeal - The horse usually squeals with its mouth closed. A squeal varies in length and loudness depending on the intensity of the situation. Often you hear a mare squeal when she did not like something that is happening or is being courted by a male. It can mean irritation with a mare, challenge, aggression or even pleasure. Mares can be really "fickle"! I have also seen mares paw with the front hooves, arch their necks and lunge forward when they squeal. The sound is a powerful exhalation of air through the nose. With stallions and geldings the body posture is usually a head and tail held high. Male horses are usually in the "fight or flight" mode when they squeal. It usually means there is concern, worry or challenge with a gelding or stallion. There is not "guess work" like with a mare.
Blow - The blow is a simple exhale through the nose but the horse has his mouth shut. The blow is much like the snort but without any vibration or fluttering noises. Curiosity, well being, happy anticipation of a good romp and ride, or the greeting of another horse will bring on a blow. The horse's body movement and the situational moment will let you figure out what the blow is all about.
Horse Blow Sound
Grunt or Groan - The grunt or groan can be considered a sign of pain as well as a sign of contentment. Once again, the environmental and situational needs must be considered. For example, if a horse grunts or groans upon landing over a jump it most likely is pain from something. I have heard horrible groaning from horses colicing. If a horse grunts or groans headed back to the barn and is in anticipation of "work day over" and I am headed for a brushing, water, feed, a bath, a great roll in the dirt and freedom in the pasture---it is most likely contentment.
Horse Grunt Sound
Roar or Trumpet - Anger, confusion, fear, rage and pain will bring on a roar or trumpet. It is really a disturbing sound. It is a sound of a horse in some kind of distress.
Horse Trumpeting Sound
Horse Roaring Sound
Scream - The scream sounds like a loud roar of rage. It is very rare to hear a domesticated horse scream. It is usually used during a fight between two horses or when a horse is in excrutiating pain. Some will tell that it is not heard from domestic horses but only horses in the wild. I have heard a domestic horse scream from pain and is most disturbing.
Horse Scream Sound
Sigh - Drawing in a deep breath, then letting it out slowly and audibly through the mouth or nostrils is a horse sigh. A sigh can mean relief from something that is bothering the horse. It can also mean release of tension. Relaxation will also bring on a sigh. Boredom can bring on a sigh. I had several horses that would sigh when being given massage. That was the release of tension. They would also pass gas during massage. When a horse passes gas during a massage it usually means total relaxation and happiness---that is, at least, for the horse not necessarily the person giving the massage.
Horse Sighing Sound
For More Information:Horses Make 8 Sounds to Convey Information, Moods