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RE: Scan wave files for silence
To: CRTech <crtech@crtech.org>
Subject: RE: Scan wave files for silence
From: Mike Shane <mshane@salemomaha.com>
Date: Tue, 4 Apr 2017 05:40:21 +0000
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Thread-topic: [CRTech] Scan wave files for silence

All flavors/versions of Adobe Audition have this feature.  I have found you can get the usable product you’re looking for more easily by first compressing the audio.  The curve I use only compresses the top above a threshold of about -12 dBfs or less by a ratio of no greater than 6:1 and amplifies the whole selection by 5 dB.  To make this curve I started with one of the stock Soft Limiters and then modified it slightly.  So I should say it’s limiting, not compressing.


When I do this I use a saved routine that first normalizes the audio to 85%, then does the limiting, then normalizes the result to 85% again.


My “sweet spot” settings for the delete silence function are -38 for more than 140ms for silence, -34 for more than 25ms for audio, and continuous silence limit usually at 250 but I vary it depending on the desired result.


I don’t know if this was fixed in later versions but I found the Stretch function will often leave little droppings in the file of a single phoneme or more that is repeated, making the speaker sound as if he is stuttering.  The early versions of Cool Edit (prior to 2000) actually did a better job and didn’t leave these, however doing a Delete Silence function on the file before a Stretch/Shrink will usually keep the artifacts from forming.  Or you can just edit them out fairly easily if it’s a short file.  But if you don’t compress or limit the audio before using the Delete Silence feature, you will indeed probably end up with an unusable file.


Just for experimentation, I have used it on Chuck Swindoll with the continuous silence limit set to 500 or 1000ms and it still finds enough to delete to knock a minute or more off the time. 


We record our local talk shows with the spot breaks minused out which leaves a file with very large gaps.  I have some settings I use to deal with that too.  Something like -58 and -54 and limit continuous to 5 or 10 thousand.  And you can create every production director’s trick of shortening a spot by having the VO overlap itself at pauses for phrasing.  Just do the limit function, set Delete Silence for about 100ms of continuous silence, run it, and you have your desired effect without any editing.  It helps if your mic gate is set at a level that will take out or reduce the level of breathing in or you edit those out first. 


The best thing about the Delete Silence function is that you can undo it.


For the original poster, you can use this function and click the “Scan for Silence Now…” button.  Then it will find the breaks and –not– remove them but tell you how many it found and how much time they amounted to in total.  I think to get the granularity you want, a continuous silence limit of 0 will be needed.


Mike Shane

Salem Media Group Omaha


From: Willie Barnett [mailto:wbradiolists@gmail.com]
Sent: Monday, April 03, 2017 9:10 AM
To: CRTech
Subject: Re: [CRTech] Scan wave files for silence


I've used "Cool Edit" to do exactly this, when I was actively involved in Production work at WFIF. :) I did, however, find a method where the find/remove silence *DID* result in not only a usable product, but a natural-sounding one. :) Finding any silence longer than 750ms, and limiting them to 750ms seemed to be the "sweet spot". ;) It worked VERY well at reducing 31 minute files to the necessary 28 minutes. :)

It took a bunch of trial & error with MANY do/undo cycles to come up with that 750ms setting... but I share it willingly and gladly. :)

As for scanning for dropped moments in LONG recordings... Cool Edit (Adobe Audition) will do that nicely, with the right parameters.




On Mon, Apr 3, 2017 at 9:40 AM, George Lake <galakejr@gmail.com> wrote:

Adobe Audition 5.0 has a built in find silence feature.  I used to use it to edit our pastors 45 minute sermon down to 30 minutes.  After removing all the none essentials and still finding the sermon to long, I use the find silence feature to shorten the pauses in his delivery.  By the way, find and remove silence in this scenario does not return a usable product!


The feature allows for customized levels for 'silence detection' and 'audio restored'.  It would also allow for the replacement of a given length (or longer) of silence with a a predetermined length of silence, and then leave a marker in the file in all the locations where the function had been executed.



References: Scan wave files for silence
(Nathaniel Steele <nathaniel.steele@icloud.com>, 31 Mar 2017 21:56:14 -0000)
Re: Scan wave files for silence
("Allard, Mark G" <MGAllard@unwsp.edu>, 1 Apr 2017 14:50:51 -0000)
Re: Scan wave files for silence
(dave allen <crtech-mail@reyware.us>, 1 Apr 2017 15:00:05 -0000)
Re: Scan wave files for silence
(Nathaniel Steele <nathaniel.steele@icloud.com>, 1 Apr 2017 17:57:31 -0000)
Re: Scan wave files for silence
(George Lake <galakejr@gmail.com>, 3 Apr 2017 13:41:25 -0000)
Re: Scan wave files for silence
(Willie Barnett <wbradiolists@gmail.com>, 3 Apr 2017 14:09:56 -0000)
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