Vitamin A is a group of unsaturated nutritional organic compounds, that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids, and beta-carotene. Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system and good vision.itamin A can be found in two principal forms in foods 1  : Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance. 2  Since the pure alcohol form is unstable, the vitamin is found in tissues in a form of retinyl ester.
pure tone is a tone with a sinusoidal waveform reciting tone such as psalm tone and recitative as in gregorian chants timbre the quality of a musical note or sound that distinguishes different types of sound production tonality a system of music based on a key center or tonic tone control a typically electronic control for affecting frequency content of an audio signal tone linguistics the pitch and pitch changes in words of certain languages tone musical instrument the audible characteristics of a musician s sound
Once in your ear, those sound waves cause your ear drum to vibrate. This sends signals to your brain that you heard a sound. Sound waves can be represented as a wavy line. Music and sounds associated with music such as bells and birds chirping create regular sound wave patterns such as this. Noises such as doors closing, traffic, or blenders make erratic wave patterns like this. The real difference between noises and music is in the patterns of their sounds waves. We tend to find regular, orderly sound waves much more appealing and label them as musical sounds. Sound waves can move through solids, liquids, and gases. Sometimes, itâs hard to image sound as something that can move.