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Negative indicate the echo is stronger than the original signal, which if left unchecked would cause audio feedback. 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 internal electronic circuitry of an active noise-canceling mic attempts to subtract noise signal from the primary microphone. The circuit may employ passive or active noise canceling techniques to filter out the noise, producing an output signal that has a lower noise floor and a higher signal-to-noise ratio .
Echo removal is the process of removing echo and reverberation artifacts from audio signals. The reverberation is typically modeled as the convolution of a (sometimes time-varying) impulse response with a hypothetical clean input signal, where both the clean input signal (which is to be recovered) and the impulse response are unknown.
Acoustic echo cancellation (AEC) is a processing algorithm that uses the knowledge of audio output to monitor audio input and filter from it noises that echo back after some time delay. If unattended, these echoes can be re-amplified several times, leading to problems including:
To maximize gain before feedback, the amount of sound energy that is fed back to the microphones must be reduced as much as is practical.As sound pressure falls off with 1/r with respect to the distance r in free space, or up to a distance known as reverberation distance in closed spaces (and the energy density with 1/r²), it is important to keep the microphones at a large enough distance ...
If it detects an answering machine message, the dialer hangs up. Often, even when the system correctly detects a person answering the call, no agent may be available, resulting in a "silent call". Call screening with a multi-second message like "please say who you are, and I may pick up the phone" will frustrate such automated calls. [citation ...
ASIO 2.3 introduced monitoring for dropouts in the audio stream. [4] ASIO bypasses the normal audio path from a user application through layers of intermediary operating system software so that an application connects directly to the sound card hardware. Each layer that is bypassed means a reduction in latency (the delay between an application ...
A special case of hot mic is the microphone gaffe, in which the microphone is actively collecting and transmitting sound gathered near a subject who is unaware that their remarks are being transmitted and recorded, allowing unintended listeners or viewers to hear parts of conversations not intended for public consumption. Such errors usually ...