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Even though angular velocity, angular
frequency and hertz all have the
dimensions of 1/s, angular velocity and
angular frequency are not expressed in
hertz,[5] but rather in an appropriate
angular unit such as radians per second.
Thus a disc rotating at 60 revolutions
per minute (rpm) is said to be rotating
at either 2π rad/s or1 Hz, where the
former measures the angular
velocity and latter reflects the number
of complete revolutions per second.](https://image.slidesharecdn.com/scienceprojectwork2-140108081531-phpapp01/75/Sound-12-2048.jpg)
More Related Content
Sound
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- 4. Sound isa physical entity, unlike noise which is the perception of sound. Sound is an high pressure wave front through a medium (such as air, or a liquid such as water, or a solid), wherein the wave front is followed by a reciprocal pressure differential behind it. Sound is produced when something disturbs the medium and sets in motion the molecules in the medium.
- 5. How sound isproduced in humans ? In humans, the sound is produced by the voice box or the larynx. Put your fingers on the throat and find a hard bump that seems to move when you swallow. This part of the body is known as the voice box. It is at the upper end of the windpipe. Two vocal cords, are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the passage of air.
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- 9. The hertz isequivalent to cycles per second. In defining the second the CIPM declared that "the standard to be employed is the transition between the hyperfine levels F = 4, M = 0 and F = 3, M = 0 of the ground state 2S1/2 of the cesium 133 atom, unperturbed by external fields, and that the frequency of this transition is assigned the value 9 192 631 770 hertz" thereby effectively defining the hertz and the second
- 12. Even though angularvelocity, angular frequency and hertz all have the dimensions of 1/s, angular velocity and angular frequency are not expressed in hertz,[5] but rather in an appropriate angular unit such as radians per second. Thus a disc rotating at 60 revolutions per minute (rpm) is said to be rotating at either 2π rad/s or1 Hz, where the former measures the angular velocity and latter reflects the number of complete revolutions per second.
- 13. When an SIunit is spelled out in English, it should always begin with a lower case letter (hertz), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase. —Based on The International System of Units, section 5.2.
- 14. Sound pressure level Sound pressure is the difference, in a given medium, between average local pressure and the pressure in the sound wave. A square of this difference (i.e., a square of the deviation from the equilibrium pressure) is usually averaged over time and/or space, and a square root of this average provides a root mean square (RMS) value.
- 15. For example, 1Pa RMS sound pressure (94 dBSPL) in atmospheric air implies that the actual pressure in the sound wave oscillates between (1 atm Pa) and (1 atm Pa), that is between 101323.6 and 101326.4 Pa. Such a tiny (relative to atmospheric) variation in air pressure at an audio frequency is perceived as a deafening sound, and can cause hearing damage, according to the table below.
- 16. As the humanear can detect sounds with a wide range of amplitudes, sound pressure is often measured as a level on a logarithmic decibel scale. The sound pressure level (SPL) or Lpis defined as where p is the root-mean-square sound pressure and pref is a reference sound pressure. Commonly used reference sound pressures, defined in the standard ANSI S1.1-1994, are 20µPa in air and 1 µPa in water. Without a specified reference sound pressure, a
- 17. HOW DOES SOUNDWORK?
- 18. Most sound waves youhear travel through air. Sound waves can also travel through water and even through solid things. You can hear your own voice because your solid skull bones vibrate. Your ears pick up the sound waves. Your ear has three main parts that let you hear. The parts are called the outer ear,
- 19. How the LarynxWorks When a person inhales and exhales, air quietly goes through the larynx. The larynx does not make noise unless the vocal cords vibrate. When a person inhales and exhales, air quietly goes through the larynx. The larynx does not make noise unless the vocal cords vibrate.
- 20. Vocal cordsare muscles that are located inside the larynx.
- 21. The larynx has twovocal cords. When a person speaks or makes a noise, the vocal cords vibrate as the person exhales and thus makes a noise. The longer the vocal stretch, the more different the noise sounds. A person can control
- 22. A persondoes not conciously think about stretching his vocal cords when he speaks. Controlling vocal cords and changing the pitch of one's voice is learned as an infant. The noise made by the larynx combined with the shape of a persons mouth gives each person a unique sounding voice. The way a person moves her mouth, tongue and lips, changes the way the noise from her larynx will sound.
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- 27. VOICE BOX INHUMANS.