Unless you have a high-end studio, and an isolation booth, and mastering
software, and a good knowledge of how to normalize the sample to be suitable
for use as prompts, the best way to record good quality prompts is to use a
telephone set in a quiet room.
The trick with "quiet" is that our brains automatically filter out noises
that we hear; so well in fact that we think a room is quiet, and in reality
there is all kinds of noise (such as airflow noise from the HVAC system,
fans in the PC, etc). Those kinds of background noises cause aliasing in the
sample, which makes for annoying background static, or just a shitty
recording, for no good reason.
So you use a closet, or a car (engine off) connected by a 75' patch cord, or
wrap a foam mattress around your head, or . . . OK, I'm being silly, but the
trick is to eliminate ALL sound. The more creepy quiet, the better. Also,
the beauty of Asterisk is that you can record on a different system, and
just transfer the recording to where you need it.
Why is the telephone such a great way to record? Because a phone by design
filters out the exact frequencies that the telephone network can't handle
anyway, and the output is the correct resolution, sampling frequency (mu-law
8000K mono), and is properly normalized as well.
Not to be annoying, but I'll say it again. Make sure the background noise is
gone. Don't be afraid to go to almost silly lengths to make this happen.
Phone and silence. Those two things will pretty much guarantee good quality
prompts every time.
Here's a bit of dialplan code to get you started:
exten => _XXXX,1,Wait(1)
exten => _XXXX,n,Record(/tmp/${EXTEN}.sln)
exten => _XXXX,n,Wait(1)
exten => _XXXX,n,Playback(/tmp/${EXTEN})
exten => _XXXX,n,Hangup()
Bruce Nik wrote:
> Hello everyone,
>
> I would like to know what type of tricks, tools, and
> environment you use to achieve the best sound quality
> possible for Asterisk IVRs. I am looking into in-house
> solutions rather than professional sound recorders or Digium
> voice overs. Do you use a Doller Store microphone? Do you use
> any specific software? Does a really expensive Sony
> microphone makes much of a difference (3-way microphone)? Do
> sound effects to normalize the sound help afterwards? How
> many Mhz do you set the sound at? Stereo? Mono? Do you close
> the windows when recording ? :) any feedback would be appreciated.
>
> Thanks,
> Bruce
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