[Freeswitch-users] Proper prompt gain/level

Bryan Smart bryansmart at bryansmart.com
Tue Jun 28 07:25:54 MSD 2011

-v is a multiplier. So, -v 0.2 reduces gain to 20% of original.

It is typical to supply professionally recorded audio with peaks boosted to 0DBFS. That is probably how the prompts were originally supplied. It makes since that -v 0.2 would reduce the max power to 20%, around -15 to -16 DBFS.

The FS build process downloads pre-processed versions of these files. Is there somewhere online that I can find the source recordings+script that produces the pre-processed files that are downloaded by the build process?


On Jun 27, 2011, at 7:32 PM, Michael Collins wrote:

On Mon, Jun 27, 2011 at 3:07 PM, Anthony Minessale <anthony.minessale at gmail.com<mailto:anthony.minessale at gmail.com>> wrote:
Have a look at the 48khz versions of the files, those should be the originals.
Someone runs a batch sox command on them to get them to the other levels.

Just for the record, the sox command used to normalize the sounds is:
sox -v 0.2 $file_in -r $rate -c 1 $file_out

The -v format is the "volume" format and if I read the sox man page correctly it means a "linear amplitude adjustment". What I can't tell from the man page is whether .2 means "reduce by 20%" or "reduce to 20%" or something else. In any case, like Tony says, we are not picky about this as long as it's not pointlessly loud.

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