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How an Audio Feedback Suppressor Works

Views: 5     Author: Site Editor     Publish Time: 2023-03-15      Origin: Site

Feedback is a real problem in live sound. It can be caused by a multitude of things. And if you're not a professional audio engineer, it's hard to know how to get rid of it without damaging your audience's ears or ruining your show.

The fastest (less than 0.2 sec) feedback suppressor on the market, the FBQ1000 is a powerful and versatile tool that can help you get through just about any live sound challenge. Use it to knock out feedback dead in its tracks for your mains and monitors, or as a sophisticated parametric equalizer to fine-tune the acoustics of your next gig.

Detecting and eliminating feedback quickly is easy with the FBQ1000's ultra-fast feedback detection algorithm, which intelligently locates up to 12 feedback frequencies per channel. Once identified, it sets extremely narrow notch filters to "destroy" feedback frequencies while the useful signal is left virtually unaffected.

Auto Mode continuously monitors the mix and resets programmed filters automatically, while Manual Mode allows you to tweak up to 24 fully parametric filters for frequency, bandwidth and gain. Open MIDI architecture makes future firmware updates and flexible communication with other gear simple.

The FBQ1000's Set-and-Forget default setting is designed to instantly get your feedback destroyer up and running. And when you want a more advanced approach, Single-Shot mode can automatically detect and destroy feedback plus lock the filter until you reset it manually. For more control, you can also program up to 24 fully parametric filters in Manual Mode for individual frequency, bandwidth and gain.

Stop audio feedback before it becomes a problem. Whether you’re a FOH engineer ringing out a PA, a singer performing in front of a small PA or a DJ controlling sound at a party, a feedback suppressor is an essential tool to keep your sound clear and undistorted.

A feedback suppressor uses an algorithm to detect and eliminate audio feedback before it even reaches the human ear, quickly and precisely eliminating any problems with sound quality. The algorithm automatically places a narrow notch filter at each frequency that feeds back, reducing the gain of that specific frequency.

Ultra-precise, 1/80-octave filters carve out offending frequencies with pinpoint precision, preserving as much of the surrounding frequency spectrum as possible. This process occurs in milliseconds and is complete before the human ear can notice anything wrong.

The latest in auto-notching algorithms deploy notches as necessary for each detected feedback frequency. Each notch is assigned an appropriate depth based on the notch step size and a maximum depth value.

Most auto-notching algorithms also allow the user to allocate a fixed (static) or floating (dynamic) set of filters. The filter with the oldest floating value is re-deployed for new frequencies as needed.

Feedback suppression using an adaptive filter model depends on an accurate model of the loudspeaker to microphone acoustic path. An inaccurate model can result in additional distortion whereas an accurate model can provide up to 10 dB of additional gain before feedback.

An audio feedback suppressor interrupts a feedback loop to eliminate audible ringing, squealing or screeching sound. Acoustic feedback is often the result of irregularities in microphones, loudspeakers and room acoustics.

The typical audio feedback suppression algorithm uses a very narrow notch filter (atten G) to reduce the gain at the feedback frequency where the feedback occurs. This method is more accurate than the manual approach where the engineer guessed where the feedback occurred and manually pulled down a fader to reduce the gain at that point in time.

AFS is also a very DSP intensive solution that requires a considerable amount of processing power. This is particularly true when comparing it to a solution that relies on adaptive filtering algorithms and decorrelation functions.

The algorithm constantly monitors incoming audio for the presence of feedback and places narrow notch filters at each frequency that feeds back, reducing the gain of each offending frequency with ultra-precise 1/80-octave filters. This process takes just milliseconds and is complete before the human ear can detect any offending frequencies.

Unlike many competitors' feedback eliminators, dbx's AFS can remove up to 6 feedback frequencies at any given moment. This allows it to be more effective and prevents multiple cases of runaway feedback.

The filters are adapted to the dynamically changing environment, notching out feedback as it arises. If the need for feedback suppression at a certain frequency no longer exists, then the filter is lifted and can be reused for new frequencies. This is especially helpful in venues that change their frequency response as the performance progresses.

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