Recording Telephone Greetings Using Computer Audio Files

Since I've been doing radio spots for my work, it was only natural for me to also record our telephone "Event Line" (a listing of our upcoming performances). Naturally, I figured that simply using the same method I'd been using for the radio spots should work fine, with the addition of holding a phone or headset up to a speaker. The results were less than spectacular, to say the least.

After doing some research, I found a way to interface an audio device (such as a computer line out or an output from my M-Audio Fast Track Pro) with a telephone line. For less than $20, I built such an interface. Here are the items I used (from RadioShack):

279-391 Modular-to-spade 12" line cord (clearance item, but my local store had it)

274-658 4-Position Barrier Strip (for neat connection of the wires)

273-1374 1:1 Isolation Transformer

42-2372 12-Ft. Shielded Cable, RCA Plug to Tinned Wires

270-1802 Small Project Enclosure (so I don't have to see the bare wires)

274-320 Mono Phono Jack to 1/4" Mono Plug Adapter (2-Pack) (gives me the option of either an RCA or 1/4" phone jack output)

Here is how to wire the line cord, transformer, and audio cable:

To use the interface, I first called the voicemail number (on a cordless phone) and went through the key presses necessary to actually record the greeting. At just the right moment, I plugged the 1/4" phone plug into the headphone output of my M-Audio Fast Track Pro (the telephone interface was plugged into a different outlet from the cordless phone). After some trial and error, I figured out that I had to unplug the homemade interface to able to use any of the touch tones after I played the audio file (the interface "seizes" the line after it is plugged in, like a music-on-hold device). After more experimentation, I got a decent-sounding greeting, complete with background music.

Though somewhat content with the above solution, I figured there had to be a way to send sound directly from my computer to the voicemail server. I found a such a method—Skype. I set the microphone in Skype to be the Creative Audigy 2, and in the Audigy 2 control panel, I set it to use "What U Hear." You can figure out the rest....

With either of the above solutions, don't be surprised by the lack of audio quality—telephones only use the 300-3400 Hz frequency range. As I discovered, it's best for the source audio file to be EQ'd to sound like telephone audio (full-frequency content only adds distortion to the greeting). For this, I used the 15-band EQ plug-in for Audacity.

Just to play around with Skype, I called Brandon, but instead of using a cheapie computer headset, I used my voice-over recording setup (MXL DRK microphone, M-Audio Fast Track Pro, and a pair of Koss Pro4A headphones). Brandon (and his wife) noted the richness of the sound quality compared with me calling from a normal phone. I also called a couple of other friends, and they also noted that. Of course, that setup is a bit overkill for Skype.



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