Noise Reduction Manual

Cross fading prevents audible clicks from being

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Unformatted text preview: ATION CHP. 5 49 APPENDIX A Tips and Frequently Asked Questions This section answers commonly-asked questions encountered when using the Noise Reduction DirectX Plug-In. What is the best order to run the effects when restoring old records? In general, you should remove the impulsive clicks and pops before running Noise Reduction on a file. 1. Run Click and Crackle Removal and then manually remove any clicks the algorithm missed. 2. Run Noise Reduction to capture a noiseprint. (Running multiple passes of Noise Reduction can also help.) Why do I hear stuttering during real-time previewing? If you are experiencing problems when previewing the Noise Reduction plug-in in real-time, there are a couple of things that you can try. Increase the DirectX buffering size in Sound Forge In any of the Noise Reduction plug-in dialogs that have preview capabilities, you can access the Preview Configuration dialog to adjust the DirectX buffering size. 1. Right-click the Noise Reduction plug-in’s title bar. A pop-up menu will appear. 2. From the pop-up menu, choose Preview Configuration. The Real-Time Preview Configuration dialog will appear. Or, right-click near the Name field and choose Configuration from the pop-up menu to display the Real-Time Preview Configuration dialog. APPENDIX A TIPS AND FREQUENTLY ASKED QUESTIONS 50 Or 3. Lower the Buffers to process per second, increase the Total playback buffers or a combination of the two settings to reduce gapping. Use a faster processor with fast floating point arithmetic As of this printing, some high-speed processors lack speed when it comes to floating point arithmetic. It is recommended that you use a processor that is optimized for floating point arithmetic. TIPS AND FREQUENTLY ASKED QUESTIONS APPENDIX A 51 Noise Reduction The following section relates to tips and questions as they apply to Noise Reduction. There are too many controls in Noise Reduction, where do I start? Although there are many controls in Noise Reduction, you can get great results if you learn how to use 4 of them: the Reduce noise by, Reduction, Noise bias, and Capture noiseprint controls. These controls appear on both the General and Noiseprint pages. To start, use the default preset (“Default for fast computers”). Reduce noise by slider Reduction Capture noiseprint Noise bias slider Below is the basic Noise reduction process: 1. Select the noise-only section using your audio editor. 2. Enable the Capture noiseprint check box. 3. Start the processing (by pressing Preview in Sound Forge, or Play in other applications). 4. Select the entire audio file, make sure the Capture noiseprint check box is unchecked and start previewing again. 5. Use the Reduce noise by and Noise bias work controls until you get the results you want. Note: Modifying the Reduction type can further improve the output quality, but is not always necessary. APPENDIX A TIPS AND FREQUENTLY ASKED QUESTIONS 52 Which Noise Reduction mode should I use? In general, Mode 0 will sound the “cleanest,” but can sound unnatural and “electronic” when the noise level is high. Mode 3 will not completely remove the noise, but will sound the most “natural.” Modes 1 and 2 are a compromise between Mode 0 and Mode 3. You may switch between the modes while previewing in real time and decide which one works the best for your needs. When trying the different modes, the Noise bias control should remain near 0 dB when using Mode 0, but it should be raised or lowered for the other modes to find the right balance. Applying Noise Reduction without a noiseprint In some cases, you may use Reduction Mode 2 and 3 without having a noiseprint by doing the following: 1. Choose the Default All for fast computers preset from the Name drop-down list. 2. Preview without selecting the Capture noiseprint check box. 3. Use the Noise bias control (with large values that are either positive or negative) and vary the Reduce noise by control to find an optimal setting. We recommend setting the Reduce noise by control to 10 dB or less, since you will probably be removing a bit of high-end frequencies. It is common to get good results with minimal control adjustments. Capturing a noiseprint on the fly You may capture a noiseprint during playback by enabling and disabling the Capture noiseprint check box. However, the audio that you are hearing might not be completely synchronized with what is being sent to the plug-in internally. When the segment of noise-only material is small, we recommend not using this method. TIPS AND FREQUENTLY ASKED QUESTIONS APPENDIX A 53 Creating noiseprint envelopes manually You may manually create noiseprint envelopes. This feature, used properly, can be a powerful technique. Use this technique when there are no sections with noise-only material. The following procedure is for practice and uses minimal settings to help you understand how this feature works. As you get accustomed to creating your own envelopes, you may create and work with custom envelopes with 6 points that will approx...
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