The AM Forum

I am doing a class presentation on speech compression and its application in AM transmitters. I need a way to capture speech waveforms and present them using power point and a digital overhead projector. Read “I need really good resolution so I can point out asymmetry, effects of compression, etc”. Our Agilent storage scopes at school won’t cut it at all.
 
Also:

For the live demo I would like to play a prerecorded voice file, run it through my compressor, and capture the output so I can visually compare it to the original uncompressed source.

Audacity does exactly what I need except the resolution of the waveforms is just to low to be useful for this project. Someone suggested using a SDR freeware package that has a good time domain display along with running Audacity as a playback device. Well that or a good scope freeware package. FYI my laptop has L-R in if needed.

Suggestions appreciated!!

Best Regards
Ted / KC9LKE

Download a free copy of Alberto's "Spectran" It should do everything you want and runs with a computer sound card.

With Audacity you should be able to expand the waveform in question. Speech patterns will be hard to capture. Single tones are not realistic.
Maybe Frank has the answer.

 

Thanks guys:

I’ll try Spectran and also see if I can expand the waveform graph on Audacity. A friend is betting that we can increase the resolution of the graph in Audacity, to a point, with a better sound card, more points. He’s pushing so I’ll give it a try.

Right Fred! A tone gives no frame of reference. Run it through a compressor and its still a sine wave, big wup. I’m addressing a group of ….oh I’ll leave that alone. I need to show a before and after speech pattern for “obvious” proof.

I’ll report what I come up with if it’s positive.

Thanks again.
Ted   

Alberto is a great guy contact him with questions. Search on "Weak Signals"
for his email address. He is involved with Perseus SDR RX. Software.

You can set the sample rate to at least 24 bits in Audacity. If that's not enough, then you'll never have enough. How this is displayed in Audacity is another issue. But unless you are realling zooming in, you should never see the individual points in an audio waveform.

All:
After following your suggestions and some time experimenting with Audacity, I found it will work out fine. In the beginning I was in rush mode, and 16 hours sleep for the week.
Thanks again!

Best Regards
Ted / KC9LKE 

Please post this work when you get it ready. Excellent subject.

haha the digital tools are great. The alternative is to capture scope video and pick out frames of interest as in the olden days.