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Controlling the reverberant time is usually a matter of increasing the amount of absorption in the room. Classical music also benefits from a long trailing reverberant field as it allows the instruments to excite the room. This is particularly effective when listening to choirs or Gregorian chant. Back before the modern public address system, churches were designed with long reverberation to carry the voice. This is the long trailing echo that you can hear in an old church. Reducing flutter echo is easily done by placing panels on opposing parallel walls in such a way that the echo cannot sustain itself. Flutter echo is mostly caused by reflective parallel surfaces that allow the echo to sustain itself. While classical music benefits from a long reverb, communication via spoken word vastly improves with shorter decay times.Ĭlap your hands in an empty room and you will hear the sound ricochet off the walls, ceiling and floor. The more panels you put up, the more energy you will absorb. Reducing the reverb decay time is usually a matter of increasing the amount of absorption in the room. Controlling first order reflections is usually the first plan of action. Because they usually arrive a few moments after the direct sound, they can interfere causing what is known as phase cancellation or comb-filtering and can make hearing what is being said difficult. These powerful reflections occur as sound echoes off nearby walls. This is the message that is being communicated and usually the most important. The direct or initial sound is the sound coming from your mouth, the instrument being played, or from the loudspeaker. Adding sound absorption to a room can easily turn a dreadful sounding space into one that is comfortable, quite effective for communication. Controlling the ambiance or reverberant field is generally done by mounting acoustic panels on the walls or hanging them from the ceiling. They can be powerful primary or first order reflections that echo off nearby surfaces, or be secondary reflections that create a reverberant field. These competing sounds are called reflections. This causes an effect known as ‘ear fatigue’ – whereby we have to work hard at listening and speak louder to be heard in an attempt to overpower other competing sounds. Once the room’s natural threshold is exceeded, conversation and communication requires much more attention.
#How does acoustic echo cancellation work full
For instance, a teacher quietly speaking in a classroom is very different than one yelling above a room full of excited kids. Without treatment, sound will echo off the walls, floor and ceiling and reach a point where the room’s ability to handle and dissipate energy has been exceeded.
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And in a recording studio, controlling the acoustics allows us to create a predictable outcome so that the recording will translate to other audio systems with relative confidence.
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In a hotel lobby or restaurant, it may simply be an attempt at controlling the reverberant time to make communication between patrons more comfortable.
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In a factory, it may have to do with safety paging. In an airport, it may be flight announcements. In a church, this may be the spoken word. Or more simply stated: taking the clutter out of the sound so that you can clearly hear the message. In general terms, controlling sound is all about improving intelligibility or our ability to comprehend what is being communicated.