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A sound speed gradient leads to refraction of sound wavefronts in the direction of lower sound speed, causing the sound rays to follow a curved path. The radius of curvature of the sound path is inversely proportional to the gradient. [2] When the sun warms the Earth's surface, there is a negative temperature gradient in atmosphere.
In the atmosphere, vertical gradients of wind speed and temperature lead to refraction. [1] The wind speed is usually increasing with height, which leads to a downward bending of the sound rays towards the ground. The same holds if the temperature is increasing with height . If the temperature is decreasing with height and the wind speed is low ...
The decrease of the speed of sound with height is referred to as a negative sound speed gradient. However, there are variations in this trend above 11 km . In particular, in the stratosphere above about 20 km , the speed of sound increases with height, due to an increase in temperature from heating within the ozone layer .
Gradient noise is a type of noise commonly used as a procedural texture primitive in computer graphics. It is conceptually different from [ further explanation needed ] , and often confused with, value noise .
Noise that has a frequency spectrum of predominantly zero power level over all frequencies except for a few narrow bands or spikes. Note: An example of black noise in a facsimile transmission system is the spectrum that might be obtained when scanning a black area in which there are a few random white spots. Thus, in the time domain, a few ...
The speed of sound depends on the medium the waves pass through, and is a fundamental property of the material. The first significant effort towards measurement of the speed of sound was made by Isaac Newton. He believed the speed of sound in a particular substance was equal to the square root of the pressure acting on it divided by its density:
The gradient of F is then normal to the hypersurface. Similarly, an affine algebraic hypersurface may be defined by an equation F(x 1, ..., x n) = 0, where F is a polynomial. The gradient of F is zero at a singular point of the hypersurface (this is the definition of a singular point). At a non-singular point, it is a nonzero normal vector.
Perlin noise is a type of gradient noise developed by Ken Perlin in 1983. It has many uses, including but not limited to: procedurally generating terrain , applying pseudo-random changes to a variable, and assisting in the creation of image textures .