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Video of the propeller of a Bombardier Q400 taken with a digital camera showing the wagon-wheel effect Video of a spinning, patterned paper disc. At a certain speed the sets of spokes appear to slow and rotate in opposite directions.
Noise, static or snow screen captured from a blank VHS tape. Noise, commonly known as static, white noise, static noise, or snow, in analog video, CRTs and television, is a random dot pixel pattern of static displayed when no transmission signal is obtained by the antenna receiver of television sets and other display devices.
Contra-rotating propellers have been found to be between 6% and 16% more efficient than normal propellers. [4] However they can be very noisy, with increases in noise in the axial (forward and aft) direction of up to 30 dB, and tangentially 10 dB. [4] Most of this extra noise can be found in the higher frequencies.
The torsional deflection of a simple cylinder cannot radiate efficiently acoustic noise, but with particular boundary conditions the stator can radiate acoustic noise under torque ripple excitation. [8] Structure-borne noise can also be generated by torque ripple when rotor shaft line vibrations propagate to the frame [9] and shaft line.
Reverse motion (also known as reverse motion photography or reverse action) is a special effect in cinematography whereby the action that is filmed is shown backwards (i.e. time-reversed) on screen. It can either be an in-camera effect or an effect produced with the use of an optical printer .
The amplifying devices in audio and radio equipment are vulnerable to a variety of feedback problems, which can cause distinctive noise in the output. The term motorboating is applied to oscillations whose frequency is below the range of hearing, from 1 to 10 hertz , [ 3 ] so the individual oscillations are heard as pulses.
Back-up beepers or an observer are required by OSHA for earth-moving vehicles with an obstructed view to the rear and no one on the ground to help guide the driver. [9] OSHA regulation 29 CFR Part 1926.601(b)(4) requires "a reverse signal alarm audible above surrounding noise level", but only when the motor vehicle has "an obstructed view to the rear".
Reversing (also known as backing up) is the process of driving a vehicle in the reverse direction in order to maneuver. Rear view mirrors are somewhat standard equipment for this endeavor. Reversing a vehicle is used as an intermediate step to complete a three point turn , J-turn , parallel park , or similar maneuver.