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In acoustics, the sound speed gradient is the rate of change of the speed of sound with distance, for example with depth in the ocean, [1] or height in the Earth's atmosphere. 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 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 .
The noise power from a simple load is equal to kTB, where k is the Boltzmann constant, T is the absolute temperature of the load (for example a resistor), and B is the measurement bandwidth. This makes the noise figure a useful figure of merit for terrestrial systems, where the antenna effective temperature is usually near the standard 290 K ...
One definition of signal-to-noise ratio is the ratio of the power of a signal (meaningful input) to the power of background noise (meaningless or unwanted input): =, where P is average power.
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
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 .
This instrument can determine the salinity, temperature and pressure variables, and then calculate the sound velocity of the water using one of the many formulae available. [ 2 ] Secondly, the speed of sound may be directly measured using a small acoustic transducer and a reflecting surface, mounted at a known distance from the acoustic center ...
EPA-identified maximum to protect against hearing loss and other disruptive effects from noise, such as sleep disturbance, stress, learning detriment, etc. [29] Ambient 0.06 70 TV (set at home level) 1 m 0.02 60 Normal conversation 1 m 2×10 −3 –0.02 40–60 Passenger car (electric) [30] 10 m 0.02–0.20 38-48 Very calm room Ambient 2.00× ...