IVR - Recording in G.711 mu-Law Format

Audacity Help Forum Windows
1

Can I use Audacity 2.0.5. to record my voice for use in a telephone exchange system? I am new to Audacity so am not sure how to change the various settings and whether it is technically feasible anyway. Please see the required recording format specifications below. Any guidance and help much appreciated. Elaine

"Recording Format Specifications
Following are the sequence of steps to be carried out for recording the voice prompts :

  1. All recorded phrases must be encoded and digitized with the following parameters.

• Format: G.711 mu-Law
• Bit Rate: 64 kbps
• Bits/Sample: 8
• Sample Rate: 8 kHz
• Channels: Mono

  1. The final standard and custom phrase recordings in English stored in .wav format on individual Data CD-ROMs (individual CDs for standard and custom speech).

  2. Each phrase recording must be stored in a separate .wav file."

2

If the file is stereo, click above Mute/Solo (where the “Hz” is) and choose Tracks > Stereo Track to Mono.

  1. Set Project Rate bottom left to 8000 Hz.
  2. File > Export… .
  3. Choose “Other uncompressed files”.
  4. Click the “Options…” button.
  5. Choose “WAV (Microsoft)” header.
  6. Choose “U-Law” Encoding (this sets 8-bit, and with 8000 Hz project sample rate means you have 64 kbps bit rate).
  7. Click OK.
  8. Name the file.
  9. Click Save.


Audacity does not burn CD’s, but you can do this yourself, ensuring you burn a data CD and not a music or audio CD.


Gale

3

Many thanks Gale. That’s really helpful.

When I listen back to the recorded audio it sounds extremely slow - is this what you would expect?

In your view, is it worth spending the time doing background atmos noise removal for short phrases for IVR?


Elaine

4

Hi Gale

Apologies, another query.

When I look at the Properties/details of the exported files it shows an audio bit rate of 352kbps rather than 64kbps. How can I change this?

Many thanks for your help.

Elaine

5

No. You have not followed the instructions correctly.

I would guess that you used the track drop-down menu to change the sample rate. That is not the way to do it.
To set the sample rate of the exported file to 8000 Hz you need to set the “Project Rate” to 8000.
The Project Rate setting is in the lower left corner of the main Audacity window.

That’s the same problem. If you set the project rate to 8000, then the exported file will have a sample rate of 8000 Hz and the bit rate will be 64 kbps.

6

On a noisy telephone system? No in my opinion, unless the noise is very high.


Gale