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Sunday, May 14, 2006

Great Sound on a Budget: Compression 101

Direct link to the mp3: http://www.archive.org/download/FDA-14-Compression/FDA-14-Compression.mp3

▼ Notes and News
• Welcome - feedback at digiaudio.podcast@gmail.com, show notes and archives at http://digiaudio.blogspot.com
• Superb podcast on audio - Sine Language (S I N E) at http://www.audio2u.com/sinelanguage.htm. By Bruce Willianms a pro audio engineer. I recommend subscribing right away. RSS feed at http://www.audio2u.com/xml/sl.xml. Compression episode: http://www.audio2u.com/pod/sl004.mp3
. My Del.icio.us Audio bookmarks are at http://del.icio.us/ghankstef/audio (html) http://del.icio.us/rss/ghankstef/audio (rss)
• Thinking of re-branding this podcast as "Getting Started with Podcast Audio" ;et me know what you think. I think I've missed some opportunity with the current title even though I like it. People searching might find it more easily.
▼ Using compression to get help great sound
• Why do we need compression and what is it for?
• The dynamic range, the difference between the soft and loudest parts of your audio signal, is typically too dynamic when recording your voice. This means the softest part is hard to hear, particularly over background noise
• Compression can limit the louder parts and boost the softer parts and limit the louder parts - thus reducing the dynamic range and leveling the the audio to some extent
• Demo before and after
▼ Most compressors have 4 parameters to set: threshold, attack, release and output gain.
• Recommendations from Bruce Williams of Sine Language podcast
• Threshold - the point at which to start compressing. If you just want to control peaks (limiting loudest parts) you can set it higher, such as -1db. Start at -10 and adjust to your liking
• Attack - how quickly to start compressing. Start at 10 milleseconds
• Release 100 milleseconds
• Output gain - since you are quieting the louder parts, you may want to boost the output.
▼ How to
• Great news - good free compressors out there:
• Use good mic technique - get close either use pop screen or move slightly off center
• Record an unprocessed signal - try to keep your peaks between -3b and -6db if you can. This may take some trial and error
• By the way this is where a hardware compressor is better. If you're too loud and go over 0 db (clip) the hardware compressor will push down on the signal and make sure is is sent to your computer under 0 db. Without the hardware compressor - you just have to make sure you don't clip
• Get close to mic but not right up against (unless you have a foam pop filter). If no filter move slightly above left or above right
Add compression: here are the settings I used for this podcast:


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