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In September 1981, Tellabs introduced the industry's first echo canceller, an advance over the original echo suppressors that synthesized an echo and electronically subtracted it. By 1990, Tellabs had grown to 2,000 employees at 25 locations globally and sales of $211 million.
The performance of an echo canceller is measured in echo return loss enhancement (ERLE), [3] [9] which is the amount of additional signal loss applied by the echo canceller. Most echo cancellers are able to apply 18 to 35 dB ERLE. The total signal loss of the echo (ACOM) is the sum of the ERL and ERLE. [9] [10]
Adaptive feedback cancellation originated during the evolution of the hearing aid. The hearing aid became digital, and as such feedback cancellation was needed. In 1980 a directional microphone was introduced in the digital hearing aid, and adaptive feedback cancellation was created to block external noise that the microphone picked up. Today ...
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Adaptive noise cancelling is a signal processing technique that is highly effective in suppressing additive interference or noise corrupting a received target signal at the main or primary sensor in certain common situations where the interference is known and is accessible but unavoidable and where the target signal and the interference are unrelated, that is, uncorrelated [1] [2] [3].
When the delay is equal to the symbol period, the blocks are denoted as symbol-spaced, while if is a fraction of the symbol period the blocks are said to be fractionally-spaced. [2] Other minimizing functions are least mean square LMS or zero forcing ZF while the architecture can be a Decision Feedback or further improved by means of known ...
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A noise-cancellation speaker emits a sound wave with the same amplitude but with an inverted phase (also known as antiphase) relative to the original sound. The waves combine to form a new wave, in a process called interference , and effectively cancel each other out – an effect which is called destructive interference .