waves_04 - 1 waves_04 SOUND WAVES flute clarinet click for...

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SOUND WAVES waves_04 1 flute clarinet click for sounds
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waves_04: MINDMAP SUMMARY - SOUND WAVES 2 Sound waves, ultrasound, compressional (longitudinal) waves, pressure, particle displacement, medical imaging, superposition principle, stadning waves in air columns, constructive interference, destructive interference, boundary conditions, pipe – open and closed ends, nodes, antinodes, speed of sound in air, period, frequency, wavelength, propagation constant (wave number), angular frequency, normal modes of vibrations, natural frequencies of vibration, fundamental, harmonics, overtones, harmonic series, frequency spectrum, radian, phase, sinusoidal functions, wind musical instruments, beats, beat frequency, Doppler Effect, Doppler radar, shock waves 2 1 2 2 v f f T k T k T f λ ϖ π = = = = = = = beat 1 2 f f f = - o o s s v v f f v v ± = ±
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3 SOUND WAVES IN AIR Longitudinal wave through any medium which can be compressed: gas, liquid, solid Frequency range 20 Hz - 20 kHz (human hearing range) Ultrasound : f > 20 kHz Infrasound : f < 20 Hz Atoms/molecules are displaced in the direction of propagation about there equilibrium positions For medical imaging f = 1-10 MHz Why so large?
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4 0 max 0 max 0 displacement min 0 max 0 min pressure Displacement of molecules Pressure variation SOUND WAVES IN AIR
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5 Ultrasonic sound waves have frequencies greater than 20 kHz and, as the speed of sound is constant for given temperature and medium, they have shorter wavelength. Shorter wavelengths allow them to image smaller objects and ultrasonic waves are, therefore, used as a diagnostic tool and in certain treatments. Internal organs can be examined via the images produced by the reflection and absorption of ultrasonic waves. Use of ultrasonic waves is safer than x-rays but images show less details. Certain organs such as the liver and the spleen are invisible to x-rays but visible to ultrasonic waves. Physicians commonly use ultrasonic waves to observe fetuses. This technique presents far less risk than do x-rays, which deposit more energy in cells and can produce birth defects. ULTRASOUND
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What is the physics of this image? CP 495 6
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7 Flow of blood through the placenta ULTRASOUND
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The speed of a sound wave in a fluid depends on the fluid’s compressibility and inertia. Speed of sound wave in a fluid ρ B v = B : bulk modulus of the fluid : equilibrium density of the fluid V V P B / - Speed of sound wave in a solid rod property inertial property elastic = v Y v = Y : Young’s modulus of the rod ρ : density of the fluid Speed of sound wave in air 331 273 T v = Above formulae not examinable 8
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The loudest tolerable sounds have intensities about 1.0x10 12 times greater than the faintest detectable sounds.
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This note was uploaded on 09/01/2011 for the course YEAR 1 taught by Professor Various during the Three '11 term at University of Sydney.

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waves_04 - 1 waves_04 SOUND WAVES flute clarinet click for...

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