![]() The molecules are in constant motion, traveling randomly and at great speed. Even a tiny region of air contains vast numbers of air molecules. (25 degrees C)Īir, like all matter, consists of molecules. Speed of sound in various mediumsĭistilled water at 77 degrees F. These terms, as well as others used in discussing sound, are best understood through an examination of sound waves and their behavior. Objective, measurable qualities of sound include frequency and intensity, which are related to pitch and loudness. Pitch and loudness, however, are subjective qualities they depend in part on the hearer's sense of hearing. ![]() Sound can be described in terms of pitch-from the low rumble of distant thunder to the high-pitched buzzing of a mosquito-and loudness. It is impossible to list them all, because anything that imparts a disturbance to an elastic medium (as, for example, an exploding firecracker to the surrounding air) is a source of sound. ![]() Familiar kinds include the vibration of a person's vocal cords, vibrating strings (piano, violin), a vibrating column of air (trumpet, flute), and vibrating solids (a door when someone knocks). ![]() The medium need not be air metal, wood, stone, glass, water, and many other substances conduct sound, many of them better than air. Technically, sound is defined as a mechanical disturbance traveling through an elastic medium-a material that tends to return to its original condition after being deformed. Wavelength is the distance between any point on a wave and the corresponding point on the next wave. Ultrasound is sound with frequencies above the range of human hearing-that is, above 20,000 hertz. Sound quality distinguishes between notes of the same frequency and intensity that are produced by different musical instruments. Sound quality, also called timbre, is a characteristic of musical sounds. Sound medium is a substance in which sound waves travel. Resonance frequency is the frequency at which an object would vibrate naturally if disturbed. Rarefaction is a region in a sound wave in which the density of the sound medium is less than normal. Pitch is the degree of highness or lowness of a sound as we hear it. Noise is a sound that is unpleasant, annoying, and distracting. Loudness refers to how strong a sound seems when we hear it. Intensity of a sound is a measure of the power of its waves. One hertz equals one cycle (vibration, or sound wave) per second. Hertz is the unit used to measure frequency of sound waves. A 3,000-hertz tone of 0 dB is the softest sound that a normal human ear can hear.įrequency of a sound is the number of sound waves that pass a given point each second. Terms used in the study of soundĪcoustics is the science of sound and of its effects on people.Ĭondensation is a region in a sound wave in which the sound medium is denser than normal.ĭecibel (dB) is the unit used to measure the intensity of a sound. There is also sound that cannot be heard, however: infrasound, below the range of human hearing, and ultrasound, above the range of human hearing. When they strike the ear, these waves produce the sensation of sound. When a drum is struck, the drumhead vibrates and the vibrations are transmitted through the air in the form of waves.
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