First post, by NY00123
Hey there,
Before I get into the details, let me ask just one thing: If someone who is reading this has got a working PC with the relevant properties, please upload a recording! I think it should be OK to do so with a microphone.
Alright, well, it may be true that the IBM 5150, along with PCs released much later, had speakers used to approximate square waves. However, on one of the very first PCs I got to use, I am not sure this is what was approximated. Nowadays, I'd say that the various beeps sounded more like sawtooth waves or "asymmetric" square waves. When I say "asymmetric", I mean that the so-called "duty cycles" of the waves are not 50%.
I think that I have got a good approximation in Audacity (http://audacity.sourceforge.net/), by generating a sawtooth wave and then applying a specific kind of equalization, using a curve file attached to this post.
I have also attempted to make similar sounds in DOSBox, although what you'd see are really quick hacks which attempt to generate "asymmetric" square waves, rather than equalized sawtooth waves. Furthermore, they don't seem to work well with some low-frequency sounds.
To understand better what I'm talking about, here are a few tests that you can make:
1. Play the attached OGG file to have a rough guess of the way a
a 440Hz "beep" would sound on such a PC.
2. Generate a tone with Audacity. Basically, you should generate a Sawtooth tone of some frequency (440Hz seems to work), then ask for Equalization under the "Effect" menu, pick "Save/Manage Curves" and import the XML file I've attached (you should rename it to have the .xml extension first) and finally select it as the curve to use. You may then listen to the result with "Preview" and apply with "OK".
This is, more or less, how I've generated the OGG file.
3. Apply dosbox-svn-pcspkr-non-true-square-wave.diff against a recent revision of DOSBox SVN. It is basically a hackish attempt to replace the true square waves with "asymmetric" ones.
4. However, here it may be more important for some that the sounds in certain games, like Keen 1 and 4, are somewhat more true to the original. This is why I've attached similar diff which combines a different patch from ripa. For the original patch, check out "dosbox_patched4.zip" from the following thread (3rd page):
ripa PC Speaker patch (was Want to use PC Speaker and not Sound Blaster in StarControl 1)
Thanks for any useful info that ones may add!
(Most important, though, is to know what are these sounds exactly.)
NY
