Trying to understand how waveforms are represented...

[Ral-Clan]

Until the past summer I was working with fairly ancient computers: an old Amiga running Samplitude, and an old Windows 98 PC running Diamond Cut Audio. These programs always displayed waveforms symmetrically (laterally). For instance here is an example waveform in both programs:





Yet the same sound loaded into Audacity on my new PC does not look symmetrical:



And it the DAW application Reaper it looks much like Audacity:


Why is this? I am missing some fundamental piece of information that lets me understand what is going on here.
At first I thought I had a DC offset problem, until I realized it was a different method of displaying the waveform data.

[kozikowski]

Sound waveforms are not symmetrical. I can edit shows from the local radio station by knowing that Debra Baer has a lovely contralto voice and most of it goes negative, unlike most normal humans and everybody else on KPCC. It makes it a snap to find her voice on the timeline.

The Audacity waveforms seem to be accurate as far as they go. I find the dB presentation to be less useful than it should be, but it does seem to be accurate, unlike the peak sound meter, which only measures one half of the waveform.

I once had a damaged sound track which was aggressively non-symmetrical. The damage didn't show up at all on the peak meter.

If I was forced to design a sound editor on a machine with seriously restricted horsepower, I would totally duplicate the top waveform for the bottom and hope nobody notices. Instead of CPU intensive calculations, I can throw that over to the award-winning Amiga graphics module.

I had an A1K.

Koz