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SOUND a range of compression wave frequencies to which the human ear is sensitive

SOUND a range of compression wave frequencies to which the human ear is sensitive. The audio spectrum extends from approximately 20 Hz to 20,000 Hz. Range of Some Common Sounds. Intensity Range for Some Common Sounds. Sounds are produced by vibrating matter. 1. reeds. 3. membranes.

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SOUND a range of compression wave frequencies to which the human ear is sensitive

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  1. SOUND a range of compression wave frequencies to which the human ear is sensitive

  2. Theaudio spectrum extends from approximately 20 Hzto20,000 Hz.

  3. Range of Some Common Sounds

  4. Intensity Range for Some Common Sounds

  5. Sounds are produced byvibrating matter. 1. reeds 3. membranes 4. air columns 2. strings Sound is a mechanical wave (longitudinal). It will not travel through a vacuum.

  6. Sounds possess the characteristics and properties that are common to all waves.

  7. Just like all longitudinal (compression) waves, sound waves possess a velocity, frequency, wavelength, phase, period, and amplitude. Sound waves also reflect, refract, diffract, and interfere.

  8. The velocity of sound in air depends on the air temperature. The speed of sound in dry air is 331.5 m/s at 0 ºC. This speed increases with temperature: about 0.6 m/s for every 1 ºC increase in temperature.

  9. Sound Probs. • What is the speed of sound in air if the temperature is 306 K? • Find the f of a sound wave moving in air at room temp (20 C) with a wavelength of .667 m. • What are the smallest and largest wavelengths that the human ear can detect at 20 C? • If you clap your hands and hear the echo from a distant wall .20 s later, how far away is the wall? • What is the frequency of sound in air at 20 C having a wavelength equal to the diameter of a 38 cm woofer loud speaker? Of a 7.6 cm tweeter?

  10. Sound generally travels fastest in solids and slowest in gases, but there are some exceptions. Medium Velocity (m/s) Medium Velocity (m/s) Air 330 Carbon dioxide 260 Helium 930 Hydrogen 1270 Oxygen 320 Water 1460 Sea water 1520 Mercury 1450 Glass 5500 Granite 5950 Lead 1230 Pine wood 3320 Copper 3800 Aluminium 5100

  11. The human ear relates amplitude to loudness and frequency to pitch.

  12. Listen to various sound frequencies here and mixtures of sound waves here. Click here to make your own sound waves. You should hear that frequency relates to pitch and amplitude relates to loudness (for a given frequency).

  13. Sound waves refract. Click here to view a simulation of the refraction of sound waves.

  14. *Fact* All objects have a natural frequency of vibration. Resonance- the inducing of vibrations of a natural rate by a vibrating source having the same frequency

  15. A resonant air column is simply a standing longitudinal wave system, much like standing waves on a string. closed-pipe resonator tube in which one end is open and the other end is closed open-pipe resonator tube in which both ends are open

  16. A closed pipe resonates when the length of the air column is approximately an odd number of quarter wavelengths. l = {(1,3,5,7,…)/4} * l • With a slight correction for tube diameter, • we find that the resonant wavelength of a • closed pipe is given by the formula: • = 4 (l + 0.4d), where  is the wavelength of sound, l is the length of the closed pipe, and d is the diameter of the pipe.

  17. An open pipe resonates when the length of the air column is approximately an even number of quarter wavelengths long. l = {(2,4,6,8,…)/4} * l • With a slight correction for tube diameter, • we find that the resonant wavelength of an • open pipe is given by the formula: • = 2 (l + 0.8d), where  is the wavelength of sound, l is the length of the closed pipe, and d is the diameter of the pipe.

  18. Oscilliscope video (saved in TAMU file) • http://scientist.wetpaint.com/page/'The+Speed+of+Sound+in+AIR+using+RESONANCE'+Lab?t=anon

  19. Sound and strings • Velocity depends on tension and mass per unit length of the string. V=√(FT/μ) FT=Force of tension in string μ=mass/unit length of string A piano string is 1.10 m long and has a mass of 9.00 g. How much tension must the string be under if it is to vibrate at a fundamental frequency of 131 Hz? What are the frequencies of the first four harmonics?

  20. Click here to see a simulation of standing waves in a resonant tube (closed and open). Learn more about resonance here.

  21. Why aren’t there “black keys”between every two “white keys”on a piano keyboard?

  22. Can you look at this chart of notes and frequencies for the “white keys” and decide where “black keys” should be placed?

  23. Now look at a graph of those values. Does this graph help you decide?

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