digital oscilloscopes

[kowalskil@alpha.montclair.edu]

The experiments listed by John (see below) sound very innovative to me.
The first subject for this semester is "waves" and I would like to try
the demos. My 1995 Vernier Catalog lists "ULI Microphone" but I can not 
find the description of software for it, except for Apple II. 

1) Can a "Digital Oscilloscope" software, mentioned by Ray, be used with ULI?
2) Can the experiments be performed with an internal microphone of MAC? How? 
3) What is used for "triggering sound collection"?
4) Any accessible reference on digital oscilloscopes for common users?

                             Ludwik K.  kowalskiL@alpha.montclair.edu
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Date: Sat, 11 Jan 1997       From: Raymond Rogoway

If you are running mac platforms, try an internet or AOL search for
"Digital Oscilloscope." I've been using it for a year and it is great.
It is shareware and very, very easy to use. I don't know what is
available for Windows platform.
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Date: Sun, 12 Jan 1997       From: Tony Wayne

Go to www.shareware.com and look for software under the topic "Spectrum."
Under the mac platform I found a BUNCH of spectrum software that does what
you are looking for. Now I'm trying to fiqure out which one to buy. -tony
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Date: Mon, 13 Jan 1997       From: John Gastineau

You can do a number of quick and interesting experiments with sound 
software which can display an FFT. 

1. Show that telephone tone signals consist of two frequencies mixed 
in roughly equal amplitude. (Puzzle for you: which digit corresponds 
to a mixture of about 760 and 1325 Hz?) How many frequencies are used 
to create the digits 0-9 plus  * and #?  (Please don't bill me for 
inadvertent calls to Australia.)

2. Take a paper towel cardboard tube. Predict the resonance
frequencies for a tube with two open ends.  Thump the tube near the
mic. Take the FFT of the resulting sound.  The lowest major
frequency component is the fundamental resonance of the tube. Find
the speed of sound from this frequency (which for shorter tubes will
be off a bit due to end effects) Try for longer tubes as well. Try 
closing one end. Predict effects.

3. Take a 4 foot packing tube. Snap fingers at one end, see this 
click in the waveform, see reflection from open (or closed) end. Note 
whether or not click waveform is inverted.  Why? Find speed of sound 
from data. 

4. Beats from tuning forks that are maybe 10Hz apart. 

In any of these experiments it will be important to play with the 
triggering of the sound collection. If  you trigger on too low an 
amplitude, you'll only see noise. If you set the trigger too high, 
you'll not gather any data. My experience with the ULI and microphone 
has been that poor triggering is responsible for half of all 
experimental troubles, and poor data collection rates or lengths for the 
other half.

> On 12 Jan 97 at 10:41, Tony Wayne wrote:
> I have a piece of sound spectrum software for the Macintosh. What
> kind of experiemtns/activities could I use it for. Here are some
> ideas I have; show the appearance sine waves for different pitches,
> show the effect of crossover componants one an audio signal by
> feeding white or pink noise through different value capacitors to 
> a speaker. -tony
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