Noise Reduction Manual

A decibel measurement by itself is technically

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Unformatted text preview: r, we at Sonic Foundry are guilty of the above mentioned crime of nomenclature as well. In this text, whenever we write -12 dB, we are usually referring to -12 dBfs or digital full scale. DirectX A set of API’s designed by Microsoft for multimedia development. A DirectX plug-in, such as the Sonic Foundry Noise Reduction DirectX plug-in, uses the DirectX Media Runtime 6.0 API. Because DirectX Media Runtime 6.0 is a standard API, a DirectX plug-in can be used in any application that supports it. APPENDIX B GLOSSARY 64 Dynamic noise Noise which varies in amplitude and frequency content over time. These noises, such as cars driving by, cannot be effectively eliminated by the Noise Reduction plug-in. Fast Fourier Transform (FFT) By breaking up a waveform into small windows and analyzing them, it is possible to display the waveform as single frequency components with discrete amplitudes. When you get a noiseprint in the Noise Reduction plug-in, you are performing an FFT analysis on the noise. Fit Size The number of discrete points that the Noise Reduction plug-in will operate on. Generally, the greater this number, the more precise the algorithm can function. FFT Size When capturing the noiseprint, this is the number of samples contained in each analysis window. The higher this number, the more precise the analysis. However, after 2048 samples the amount of quality gained versus the added amount of processing time is low. Frequency The number of times something happens in a particular time interval. In the measurement of sound, frequency is defined as cycles per second or Hertz. Humans perceive frequency as pitch. The higher the frequency, the higher the pitch and vice versa. Glitch Any unpleasant, garbled, grungy sound in your waveform. The Click and Crackle Removal plug-in can remove these types of noise. High-shelf The Noise Reduction plug-in comes with an EQ section that can compensate for highfrequency loss during the noise reduction process. The High-shelf will boost all frequencies above the set cutoff frequency. Hertz (Hz) The metric unit for frequency, or cycles per second. Interpolate To interpolate is to make a logical guess as to what happened between two points in time. The Click and Crackle Removal plug-in can use interpolation as one of its means to remove clicks and glitches. GLOSSARY APPENDIX B 65 Noiseprint The noiseprint is an FFT analysis of the noise in your recording. The Noise Reduction plugin uses the noiseprint to determine the envelope it then uses to remove the noise. Overlap During the FFT analysis of the noise, the Overlap control determines controls the amount of overlap between frequency analysis windows. Overlapping allows for more accuracy of the analysis. Some overlap is necessary for accurate frequency analysis; however, it is not recommended that you increase the overlap past 75%. The processing time will greatly increase, but the quality will not increase proportionally. Residual Output The residual output of the Noise Reduction plug-in is the sound data that is being stripped out of the sound file. Listening to this output can be beneficial to determine how much of the source material is being thrown out with the noise. Sample In a 16-bit, 44.1 kHz sound file, a sample is one single 16-bit value that is 1/44100 seconds long. A single sound file (which contains millions of the above) can also be called a sample. Steady-state noise Noise that does not vary much in average amplitude and frequency content. The Noise Reduction plug-in reduces this type of noise very well. Windowing The windowing controls in the Noise Reduction plug-in determine the size and the overlap of the windows used during the FFT analysis of the noise. For more information, see Windowing area on page 26. APPENDIX B GLOSSARY 66 GLOSSARY APPENDIX B i Index Click removal amount, 43 A Activation code, 7 Click shape slider, 37 Assignable FX, pre-fader function, 61 Clicks, removing, 43 Attack speed slider, 16, 44 Clipped peak restoration, 45–47 using, 46 with Sound Forge, 58 Attack speed, defined, 16 Attenuation slider, 46 Audio Plug-in Chainer (Sound Forge), 55 Clipped peak restoration reference, 46 Attenuation slider, 46 Cross fade edges, 47 Enable post limiter, 47 Buffer size, increasing, 49 Code activation, 7 B Computer ID number, 7 C Computer requirements, 5 Cakewalk Pro Audio using Noise Reduction with, 13 Click and crackle removal, 35–39 limitations, 35 retaining cymbal hits, 62 tips and FAQ, 62 using, 36 with Sound Forge, 56 Click and crackle removal reference, 37 Click shape slider, 37 Keep residual output, 39 Max click size slider, 38 Noise level, 38 Remove low-frequency rumble, 39 Sensitivity slider, 37 Click and crackle vs. Vinyl restoration, 62 Cross fade edges, defined, 47 E Eight-bit files, 54 Email technical support, 8 Envelope point creating manually, 53 Envelope points adjusting, 19 adjusting for high-frequency, 54 fitting, 21 moving group, 20 moving one, 20 resetting, 21 INDEX ii Envelopes, 29 amplitude, 30 I European contact...
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