Noise Reduction Manual

2 35 chapter 3 click and crackle removal clicks and

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Unformatted text preview: n the normal curve of a waveform. Click/crackle The Click and Crackle Removal function finds these glitches and automatically replaces them to minimize their audibility. Limitations The click and crackle removal algorithm is designed to find and remove pops and clicks, not broadband or long “scratch” noises. After removing any clicks and crackles, it is suggested that you use the Noise Reduction function to remove other background noise. For more information, see Noise Reduction on page 9. CHP. 3 CLICK AND CRACKLE REMOVAL 36 Using Click and Crackle Removal The primary way to use the Click and Crackle Removal function is to select a region in a sound file and have the function detect and try to automatically remove all clicks found. Presets As you will discover, the presets will provide great results without control adjustments. The controls are included for making minor adjustments and for individuals who like to experiment. Several presets are supplied to get you started. In general, either the Default for 78 RPM or the Default for vinyl recordings preset is the best starting point if you have a fast machine (200 MHz or higher). The Basic setting for slower computers preset should be used as a starting point for real-time preview if you experience stuttering during playback. In some host applications, you may be able to disable real-time preview if you continue to experience performance problems. recordings The Click and Crackle Removal presets may be adjusted using the controls. Since each control affects the output significantly, we recommend spending some time trying different variations. As you experiment, you will learn how each control changes the output. In some cases, adjusting a control will not produce significant audible changes. Not detecting the changes is not due to your “understanding” of how to adjust the controls, but rather due to the underlying algorithm. This algorithm is performing many tasks behind the scenes. Explaining the algorithm’s tasks may cause confusion, since they are not intuitive to real-world applications. CLICK AND CRACKLE REMOVAL CHP. 3 37 Click and crackle removal reference This section explains the function of each control in the Click and Crackle Removal dialog box. Sensitivity (1 to 20) The Sensitivity setting determines how sensitive the detection algorithm is to “impulsive” sounds. With settings below 10, only very significant clicks will be removed. Between 10 and 17, smaller clicks will also be removed. Above 17, tiny clicks that cause crackling will also be removed. Vinyl LP recordings can usually be cleaned satisfactorily with settings of 12 to 16. However, some vinyl which has been abused will need higher settings and in extreme cases the maximum setting may do the best job. The best settings for 78 RPM recordings tend to run from 16 to 19, but really noisy 78s may require the maximum setting for best results. When very aggressive Sensitivity settings are necessary to clean up the material at hand, the control can be used to prevent damage to percussive attacks by setting it to 1.0 millisecond or less. Click shape Click shape (1 to 8) The Click shape setting determines the type of clicks the algorithm detects. In most cases, it should be left between 4 and 6. With settings above 6, very small, high-frequency clicks will be more easily detected. With settings below 4, larger pops will be detected more easily. Since the clicks from old 78s are generally made up of a lower frequency distribution than LPs, settings of 3 and 4 tend to detect them better. The clicks from LPs with a greater amount of high frequency content are detected better with larger settings such as 6 or 7. CHP. 3 CLICK AND CRACKLE REMOVAL 38 Max click size (.1 to 3.0 milliseconds) The Max click size setting establishes the longest click that will be detected by the algorithm. In most cases, the default setting of 3 milliseconds works well. Lower settings can be useful if you want to remove only small clicks or crackling. However, if your file has large amounts of cymbals, snare drums, castanets, etc., they could get confused with clicks. So, lower settings (such as 1.0 ms) will prevent these fast attacks from being removed. If you look at the wave form of castanets, brushes on high-hat cymbal, blocks, maracas, or claviers (and numerous others) you will see that their sound waves actually look very similar to clicks, but last for a slightly longer time. If your material has these kinds of percussion sounds the size setting might need to be about 0.8 ms to protect them. However, when this setting is set to a low value, you will often have to manually remove larger pops that are missed by the algorithm. You will have choose a setting based on how much loss is acceptable and how much time you can spend manually de-clicking these missed clicks. Noise level (Low, Medium, High) The Low and Medium noise level settings split the audio input into noise and non-noise portions, and clicks are removed from only the noisy part of the audio....
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This note was uploaded on 05/15/2013 for the course EMUS 201 taught by Professor Pardal during the Winter '10 term at Life.

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