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Modern particulate samplers use a volumetric flow control system that pulls air through the particle separator at the velocity required to achieve the desired cutpoint. For air pollution applications, the definition of "particulate" does not include uncombined water , and water from a particulate sample must be removed before it is weighed.
A sampler is an electronic musical instrument that records and plays back samples (portions of sound recordings). Samples may comprise elements such as rhythm, melody, speech, sound effects or longer portions of music. The mid-20th century saw the introduction of keyboard instruments that played sounds recorded on tape, such as the Mellotron.
The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air, is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn), or 1 km in 2.91 s or one mile in 4.69 s.
An impactor is a device that classifies particles present in a sample of air or gas into known size ranges. It does this by drawing the air sample through a cascade of progressively finer nozzles. The air jets from these nozzles impact on plane sampling surfaces and each stage collects finer particles than its predecessor.
The virtual temperature of an air parcel is the temperature that dry air would have if its pressure and density were equal to those of a sample of moist air. As a rule of thumb, an atmospheric vertical velocity of 1 m/s (3.3 ft/s) can alter a TV observation by 1.6 °C (2.9 °F).
For example, Compact Disc Digital Audio and Digital Audio Tape systems use different sampling rates, and American television, European television, and movies all use different frame rates. Sample-rate conversion prevents changes in speed and pitch that would otherwise occur when transferring recorded material between such systems.
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The simplest way to change the duration or pitch of an audio recording is to change the playback speed. For a digital audio recording, this can be accomplished through sample rate conversion. When using this method, the frequencies in the recording are always scaled at the same ratio as the speed, transposing its perceived pitch up or down in ...