ultrason

CONT: Les ultrasons sont des vibrations produites dans la matière à une fréquence supérieure à la limite d'audibilité des sons, qui dépend de l'âge (15 Hz à 20 kHz). La limite supérieure est de plusieurs milliers de kilohertz.
OBS: ultrason : Cette graphie, puisée des Rectifications de l'orthographe recommandées par le Conseil supérieur de la langue française, est attestée dans le Petit Robert (2006).

CONT: Originally sound referred entirely to what is heard. Later, however, interest developed in sounds which human beings cannot hear, either because the frequency is too low (infrasound) or too high (ultrasound).
CONT: Sound waves of extremely high frequencies are an important tool in probing basic properties of matter and in gaining a better understanding of important physical phenomena, such as thermal vibrations and superconductivity. The frequencies of the sound waves that are used for such purposes often exceed the audible range (ultrasound) and may be as high as several billion cycles per second (hypersound).