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Trumpet Acoustics
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Trumpet Acoustics |
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Rijke Tube
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Rijke's tube turns heat into sound, by creating a self-amplifying standing wave. It is an entertaining phenomenon in acoustics and is an excellent example of resonance. P. L. Rijke was a professor of physics at the Leiden University in the Netherlands when, in 1859, he discovered a way of using heat to sustain a sound in a cylindrical tube open at both ends. He used a glass tube, about 0.8 m long and 3.5 cm in diameter. Inside it, about 20 cm from one end, he placed a disc of wire gauze as shown in the figure at right. Friction with the walls of the tube is sufficient to keep the gauze in position. With the tube vertical and the gauze in the lower half, he heated the gauze with a flame until it was glowing red hot. Upon removing the flame, he obtained a loud sound from the tube which lasted until the gauze cooled down (about 10 s). It is safer in modern reproductions of this experiment to use a Pyrex tube or, better still, one made of metal.
Source : Wikipedia |
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Beats
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In acoustics, a beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is the difference between the two frequencies.
With tuning instruments that can produce sustained tones, beats can readily be recognized. Tuning two tones to a unison will present a peculiar effect: when the two tones are close in pitch but not yet identical, the difference in frequency generates the beating. The volume varies like in a tremolo as the sounds alternately interfere constructively and destructively. When the two tones gradually approach unison, the beating slows down and disappears.
Source : Wikipedia |
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Mersenne's Laws
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Mersenne's Laws |
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AM, FM and Balanced Modulation
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Three important types of Modulations are discussed. Amplitude Modulation, Frequency Modulation and Balance Modulation are discussed. Two signals are considered in modulation. The Carrier signal and the Modulator signal. |
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Reflection of Pulses
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Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection. In acoustics, reflection causes echoes and is... |
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Sound Reflection from Concave Surfaces
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Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection. In acoustics, reflection causes echoes and is... |
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Sound Refraction - Sound Lens
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Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one medium to another. Refraction of light is the most commonly observed example, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another or when water waves move into water of a different depth. Refraction is described by Snell's law. In optics, refraction occurs when light waves travel from a medium with a given refractive index to a medium with another. At the b... |
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Standing Waves in Air Columns
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Standing Waves in Air Columns is demonstrated. Nodes and antinodes are excited by a tuning fork for pipes that are open-open and open-closed. A classic demonstration of the Rayleigh's Criteria (widely used in studying combustion stability in aircraft, rocket and gas turbine engines) is demonstrated using a heated wire gauze placed inside a pipe at a suitable location inside the tube. This is called the Rijke Tube experiment. |
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Frequency, Amplitude and Tone Quality
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Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency. For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles, or periods, per unit time. In physics and engineering disciplines, such as opt... |
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