Digital signal processing, or DSP for short, is the act of changing and manipulating digital signals. In our use-case as audiophiles the digital signal is audio, but be aware that the digital signal can be other things in different industries. There are many different ways to change an audio signal, and many different purposes to do so. Here are some of the most common DSPs you will come across in audio editing software and hardware:
Equalization (EQ): EQ is a tool that gives us the ability to boost or attenuate a range of frequencies in a sound. EQ is probably the most common DSP available to sound engineers. One such use case for EQ is removing unwanted sounds from a recording—If your dialogue recording has an annoying hum in the low end, then an EQ will allow you attenuate the low-end frequencies to make the hum nearly inaudible.
Compression: Compression is a tool that will level-out the dynamic range of a signal. For example, if your recording is too quiet at some parts and too loud at others, you can use a compressor to even-out the overall loudness of the whole recording, essentially making the quiet parts louder and the louder parts quieter.
Limiters: These are very similar to compressors except they have a hard ceiling. This means that an audio signal will never pass the volume at which you specify. Comparatively, a compressor will be gentler and slow push the audio signal below your specified volume.
Gates: These DSPs are the reverse of a limiter, where they will cut off an audio signal if it gets too quiet.
Expanders: These are like the inverse of a compressor, where they will attenuate sounds that are very quiet but not remove them entirely (like a gate will.)
Reverb: Short for reverberation, reverb is an effect that causes a sound to persist for a longer deration as a multitude of reflections. This essentially mimics the reflective properties of a large room, where sound waves can bounce around for a long period of time, which causes a sonic “tail” that slowly gets quieter until it’s inaudible.
Delay: This is an effect that duplicates a sound and plays it back after a period of time. A delay unit will usually allow you to choose how many times to duplicate the sound and how loud the duplication is. This effect, like reverb, mimics the acoustic properties of a room, where sound can bounce off of walls.
These are the main DSPs that you’ll encounter as a sound engineer. There are countless other tools out there, but more or less they are just variations and combinations these foundational ones.
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