The Oxford DeBuzzer from Sonnox is a plug-in that removes hum and buzz from audio material and is divided two stages - detection and removal. For the process to work well, the fundamental frequency must first be very accurately defined.
The plug-in features several ways of helping isolate the fundamental frequency. First is the Peak Profile that shows the strength of a given nominal frequency in the input signal. Second is the large FFT display which accentuates any frequency components that are consistently present, making them stand out in the plot. It will automatically mark the three highest peaks found, and the nominal frequency can then be set by clicking one of the peaks on the graph.
The third method uses a tone generator in the same way that one can tune a guitar. As the generated tone moves closer to the fundamental, the beat frequency between the tone and the fundamental will become slower and slower. Noise removal is accomplished using a comb filter. The comb filter has multiple tight notches that eliminate the fundamental frequency and associated harmonics.
- Tracking Modes
- Fast, Auto and Freeze modes
- By default the plug-in assumes Auto mode, continuously hunting either side of the nominal frequency for a peak profile
- Once the lock strength rises to be above a certain level, the plug-in automatically sets the nominal frequency to the frequency of the peak found
- If the hum is wandering in frequency, the detector will follow
- Auto Mode is suitable for tracking a weak, slowly wandering fundamental and operates over all three frequency bands
- Fast tracking mode allows the removal filters to automatically follow a quickly wandering fundamental
- Freeze Mode is best used for removing whines and whistles along with the use the FFT to find the frequency of the whines
- Filter Choice
- The default removal filter is a comb filter
- Para-EQ mode overrides the default allowing for use of the parametric EQ sections to remove the fundamental and harmonics
- In Para-EQ mode attenuation can be reduced as frequency is increased using the Slope control
- It is possible to choose to notch out odd and even harmonics, as opposed to only odd harmonics
- The listen section of the Output Panel labeled "Diff" contains an option to listen to the difference between the input and the processed output
- Particularly useful for hearing what has been repaired, and for listening to the quality of the repairs without being distracted by the audio material