🐴 How can horses produce low and high sounds at the same time?

The horse's whinny impresses with its unique acoustic signature, clearly blending low and high tones. How does this equine achieve such a sound mix? This question led a research team to closely examine the vocal mechanisms of this animal.

Their observations, published in the journal Current Biology, indicate that horses employ a remarkable vocal technique. They simultaneously generate two distinct sounds: a low tone originating from the vibration of their vocal cords, and a high-pitched whistle produced within their very larynx. This combination allows for the emission of denser messages in a single vocalization.


To decipher this phenomenon, scientists analyzed the vocal anatomy of horses and conducted precise acoustic measurements. By combining approaches from veterinary medicine and sound physics, they were able to locate the origin of the whistle. It comes from an air turbulence in the larynx, similar to a human whistle but generated internally.

Tests using helium confirmed this observation. By passing this gas through horse larynxes, the researchers noted that the frequency of the whistle increased, while the low sound remained stable. This divergence confirms that the two acoustic components are created by independent mechanisms.

This ability, called biphonation, appears as an evolutionary adaptation. It allows horses to communicate diverse information, such as their emotional state, in a single vocal emission. Przewalski's horses, close relatives of domestic horses, also possess this characteristic, which is not the case for donkeys or zebras.

This work offers new insight into vocal diversity among mammals. By understanding how horses developed this technique, it becomes possible to better grasp the evolution of animal communication.

The potential implications extend beyond basic research. They could, for example, facilitate better understanding between horses and humans, in activities such as horseback riding or equine welfare management. Future research will focus on how these signals are perceived and interpreted in the natural environment.