Audacity CleanSpeech Audio Editor
CleanSpeech is a free alternative to other audio editors that are oriented for
preparation of music. It is derived from Audacity, with
simplifications and enhancements aimed at improving the clarity of speech and
Here are several scenarios where CleanSpeech is appropriate:
- church has backlog of sermons they want to make available for distance listening
(the original name of this freeware was SermonEditor)
- school has backlog of recorded classroom lectures they want to upload
to their website for distance learning
In contrast to most users of audio editors, speech processing has these differences:
- noise reduction is a much bigger factor (originals can be ghastly, equivalent to old 'bootleg tapes')
- leveling is a much bigger factor (soft sections made louder and vice versa)
- dynamic range (dr) is the 'enemy'
- dr works well in 'live performance' to hold attention and make points
- can cause big problems for 'distance listeners'
- won't be able to hear the soft sections that are lost
in the ambient noise and hiss/hum.
- will find themselves reaching for the volume control to
manually cut down shouting and boost whispering
- fidelity to original less critical than leveling ...
with low quality originals, it is ok to tradeoff better clarity for
lower fidelity and more distortion ("that doesn't really sound all
that much like Joe ... like maybe he has a cold, but at least I can
make out what he was saying")
- truly huge files for the masters, and file compression that preserves
as much clarity and quality at 16kbps is very important
- end result is almost always mono
- truncate silence a much bigger issue ... the 'distance listener' can
hit the pause button whereas the instructor may be fine with a five minute gap
while the lab is prepared, for example.
- end-user doing speech processing often bored volunteer with obsolete equipment
- without scripting, it is error prone and beyond tedious to
manually apply the same series of 'effects each time
(stereo-to-mono as applicable, .mp3 to .wav as applicable,
normalize, click-removal, equalization, noise reduction,
leveling, truncate silence, renormalize, resample to 11025,
convert to 16kbps .mp3)
- each 'effect' may take several minutes
- manually starting each effect when the previous one finishes is exasperating
... volunteers would prefer to 'kick on the chain of effects',
take a break, and come back when it is finished.
- typical end-users of other audio editors is a person with a relatively high
level of computer literacy who is willing to spend hours
or days getting a multitrack mix just right for a demo CD.
- may be dozens or hundreds of 'speeches' to process, so batching is very valuable
For both distance learning and sermons, many of the 'speeches' would share common
attributes as far as the noise level and dynamic range used by the speaker.
Once noise-reduction and leveling factors are identified, the same factors
can suffice for some, many, or most of the subsequent speeches.
This can be a huge time saver, and allow overnight processing.