How to make CCITT mu-law files for older IVR systems using Audacity

Hey, there!

I came THIS close to spending nearly $400 this weekend that I didn’t need to.

I was saved by experimentation. And I’m going to save you too – especially if you do IVR work for older phone tree systems.

Here’s how.

(And do refer back to this little snippet of a screenshot when I reveal this Secret.)

So, what’s the secret of using Audacity to create phone prompt WAV files for ancient IVR systems?

I do a lot of IVR work – and it’s one of my most popular classes. I’m the on-hold voice, the voice you get mad at while you’re waiting for the opportunity to get mad at a real live person, for many of the Fortune 5000, including AOL.

AOL has systems that go back decades (I’ve been their voice since 1988), and although I can send them WAV or MP3 files for the modern systems they use, those older legacy systems are really picky about what kind of files they can play to callers.

In fact, they are so old and outdated that most sound converters don’t even offer the option to convert regular old WAV files into what these older systems want.

(For you techies, the older systems don’t want standard PCM encoded 16 bit 44.1K full fidelity WAV files, they want CCITT mu-law encoded 8 bit 8K files. Why? Storage was a premium consideration in The Old Days – these files are tiny compared to standard WAV files.)

I recently revamped my studio, and got rid of a number of older Windows machines, one of which had an app built into the operating system that would convert these files just fine.

But…alas, no longer do I have that tool at my disposal.

And after hours of testing every Macintosh sound editing and conversion software out there, including Switch, Sound Converter, Fission, ProTools, ffmpeg and front-ends for ffmpeg, And I finally found an expensive solution: BarbaBatch. The demo worked like a charm on my files.

Problem: BarbaBatch costs $395. Ick. But, I was ready to buy it – I mean, AOL pays me big bucks to do their phone prompts, and they need to be kept happy.

But, I kept searching. And searching, and searching. And in the week hours of Sunday morning, I stumbled on a process, posted not on a VO site, but on a Cisco tech site, that would allow me to use good old Audacity:

First, record and normalize your prompt in mono.

Then, in the lower left hand corner of your Audacity project screen, change the Project Rate to 8000 (it will most likely be at 44100).

Then, export your file using the “Other Uncompressed Files” option in the Save dialog box, and choose WAV (Microsoft) as your Header and U-law as your Encoding in the drop down menus. Then, save your file with the .wav extension.

Voila. CCITT mu-law (aka U-law) 8k 8-bit mono wav files.

My client at AOL confirmed that they worked perfectly on their older systems, and actually sounded better than any of the BarbaBatch converted samples.

Nothing about this process was even remotely intuitive, but it worked. And as a VO artist with a home studio and a bent to serve clients, these are the little skills you never know whether or not you’ll need – until you need them.

I hope this helps. And I hope you get the kind of IVR gig that I’ve had with AOL for the last 28 years or so – and NEED this!


3 Responses to How to make CCITT mu-law files for older IVR systems using Audacity

  1. Earl Hinton August 7, 2013 at 3:16 pm #

    I’ve used Audacity a few months ago but had forgotten the steps to save as an 8bit 8KHz Mu law wave file. This article has certainly saved me some time from fumbling around. I manage and coordinated all of the voice announcements in our Avaya Communication Manager and I’m always looking for sound advice. I rarely record any of the announcements in my own voice, however I will bookmark for future reference.

    E. Hinton
    Telecom Mgr.
    Affinity Health Plan

  2. Mike Coon February 8, 2014 at 2:04 pm #

    Thanks David!

  3. Mark June 26, 2014 at 2:52 pm #

    I’d been working with Avaya for many years and had figured this out at one point. However, after taking a 5yr break I had forgotten–thanks for the reminder!

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