Our hearing is one of our most important senses, necessary for basic communication, speech and awareness. But have you ever stopped to think, what exactly is sound? And how do our ears actually work?
Sound is caused by something emitting energy in the form of a vibration. Areas of high and low pressure move outwards creating a form of longitudinal wave (a wave which vibrates in the direction of travel). The amplitude (volume) and frequency (pitch) of the sound wave depends on what the source is and the amount of energy supplied outwards.
But how do we sense and process these sound waves? That’s the job of our ears. The ear is an extremely clever organ, consisting of a collection of tiny bones, tubes and membranes (namely the ear drum) which process the sound and send it to the brain. The funnel-like shape of the ear is effective at collecting the sound wave and filtering it through the ear passage, where it causes vibrations of the ear drum. The signal is gradually converted into an electrical signal by the rest of the ear, and this is then sent to the brain.
Many species use sound, not only to communicate but to assess the nature of their surroundings, dependant on the way they interact with emitted sound waves. For example, if you screamed in a large, empty room, the sound of your voice would sound a lot different than if you were to make the same noise in a smaller furnished room. Studying the interaction of sound waves with certain materials can tell scientists a lot of information about that material.
Ultrasound is another important area of study, especially in construction and medicine. High frequency sound waves are sent through the area of interest, for example the human body or an iron girder, and the waves that are reflected back to the receiver tell us about the internal structure of the object.
Information from http://www.sciencemadesimple.co.uk/activity-blogs/sound