A system, comprising: a first host associated with a presenter, which in operation, runs an application or presents a presentation material to share at a conference call; a voice audio engine running on the first host, which in operation, accepts a voice conference audio stream from the rest of the conference call; a sound mixing component running on the first host, which in operation, accepts and provides a mix of the voice conference audio stream and a computer audio stream of the application or presentation material to a switch engine and to one or more speakers associated with the presenter; said switch engine running on the first host, which in operation, accepts as a first audio input a microphone audio stream captured by a microphone associated with the presenter, the microphone audio stream including the presenter audio as well as possible feedback from the mix of the voice conference audio stream and the computer audio stream captured by the microphone from the one or more speakers, and accepts as a second audio input the mix of the voice conference audio stream and the computer audio stream captured from the sound mixing component; selects and outputs only one of the first and second audio inputs as its audio output to the voice audio engine upon a triggering signal; wherein, in operation, when the first audio input is selected as the audio output from the switch engine, the voice audio engine processes the voice conference audio stream and the mix of the computer audio stream and voice conference audio stream from the sound mixing component to cancel the feedback of the voice conference audio stream from the first audio input, thereby producing a cleaned presenter audio stream, and transmits the cleaned presenter audio stream to the rest of the conference. a first host associated with a presenter, which in operation, runs an application or presents a presentation material to share at a conference call; a voice audio engine running on the first host, which in operation, accepts a voice conference audio stream from the rest of the conference call; a sound mixing component running on the first host, which in operation, accepts and provides a mix of the voice conference audio stream and a computer audio stream of the application or presentation material to a switch engine and to one or more speakers associated with the presenter; said switch engine running on the first host, which in operation, accepts as a first audio input a microphone audio stream captured by a microphone associated with the presenter, the microphone audio stream including the presenter audio as well as possible feedback from the mix of the voice conference audio stream and the computer audio stream captured by the microphone from the one or more speakers, and accepts as a second audio input the mix of the voice conference audio stream and the computer audio stream captured from the sound mixing component; selects and outputs only one of the first and second audio inputs as its audio output to the voice audio engine upon a triggering signal; wherein, in operation, when the first audio input is selected as the audio output from the switch engine, the voice audio engine processes the voice conference audio stream and the mix of the computer audio stream and voice conference audio stream from the sound mixing component to cancel the feedback of the voice conference audio stream from the first audio input, thereby producing a cleaned presenter audio stream, and transmits the cleaned presenter audio stream to the rest of the conference. accepts as a first audio input a microphone audio stream captured by a microphone associated with the presenter, the microphone audio stream including the presenter audio as well as possible feedback from the mix of the voice conference audio stream and the computer audio stream captured by the microphone from the one or more speakers, and accepts as a second audio input the mix of the voice conference audio stream and the computer audio stream captured from the sound mixing component; selects and outputs only one of the first and second audio inputs as its audio output to the voice audio engine upon a triggering signal;