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DC Offset
DC offset occurs when hardware, such as a sound card, adds DC current to a recorded audio signal. This current results in a recorded
waveform that is not centered around the baseline (-infinity). Glitches and other unexpected results can occur when sound effects are
applied to files that contain DC offsets. Sound Forge software can compensate for this DC offset by adding a constant value to the
samples in the sound file.
In the following example, the red line represents the baseline. The lower waveform exhibits DC offset; note that the waveform is
centered approximately 2 dB above the baseline.
Decibel (dB)
A unit used to represent a ratio between two numbers using a logarithmic scale. For example, when comparing the numbers 14 and 7,
you could say 14 is two times greater than the number 7; or you could say 14 is 6 dB greater than the number 7. Where did we pull that
6 dB from? Engineers use the equation dB = 20 x log (V1/V2) when comparing two instantaneous values. Decibels are commonly used
when dealing with sound because the ear perceives loudness in a logarithmic scale.
In Sound Forge software, most measurements are given in decibels. For example, if you want to double the amplitude of a sound, you
apply a 6 dB gain. A sample value of 32,767 (maximum positive sample value for 16-bit sound) can be referred to as having a value of 0
dB. Likewise, a sample value of 16,384 can be referred to having a value of -6 dB.
Device Driver
A program that enables Windows to connect different hardware and software. For example, a sound card device driver is used by
Windows software to control sound card recording and playback.
Destructive Editing
Destructive editing is the type of editing whereby all cuts, deletes, mixes and other processes are actually processed to the sound file.
Any time you delete a section of a sound file in Sound Forge software, the sound file on disk is actually rewritten without the deleted
section.
See also Nondestructive Editing on page 352.
Digital Rights Management (DRM)
A system for delivering songs, videos, and other media over the Internet in a file format that protects copyrighted material. Current
proposals include some form of certificates that validate copyright ownership and restrict unauthorized redistribution.
Digital Signal Processing (DSP)
A general term describing anything that alters digital data. Signal processors have existed for a very long time (tone controls, distortion
boxes, wah-wah pedals) in the analog (electrical) domain. Digital Signal Processors alter the data after it has been digitized by using a
combination of programming and mathematical techniques. DSP techniques are used to perform many effects such as equalization and
reverb simulation.
Since most DSP is performed with simple arithmetic operations (additions and multiplications), both your computer’s processor and
specialized DSP chips can be used to perform any DSP operation. The difference is that DSP chips are optimized specifically for
mathematical functions while your computer’s microprocessor is not. This results in a difference in processing speed.
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