Visual Analyzer

Amazing Virtual Audio Test Lab for
Windows

Visual Analyser is a freeware Windows application,
written by an Italian engineering student, that converts your soundcard into the
equivalent of an entire rack of Hewlett-Packet audio test gear.  Using both
the soundcard inputs and outputs it creates:

• A dual-trace audio oscilloscope
   
• An audio spectrum analyzer
   
• An RMS or peak-reading AC voltmeter
   
• An audio frequency counter
   
• An audio phase meter that can read the phase
  difference between the two channels
   
• An audio distortion meter that can do SINAD-type
  measurements
   
• An audio function generator that can produce sine,
  square, sawtooth and pulse waves.
   
• An audio sweep generator that can track the scope
  to create audio frequency-response plots.
   
• With some home-brewed external circuitry, an RLC
  Z-meter that can measure inductance and capacitance values

With a high-quality sound card such as the Behringer
UCA202 external USB sound device reviewed here,

   
Behringer
UCA202 Review ,

the capabilities of these virtual instruments come very
close to the classic hardware versions.’ Download this fantastic freeware tool at:

   
http://www.sillanumsoft.org

Versions are available for both 32- and 64-bit Windows
systems. The application will run on any version of Windows from Windows XP
onward.

After downloading and installing the application, starting the program
should yield this screen.

Initially the button in the far upper-left corner will
be “un-pushed” and show “On” (meaning click to turn on the instruments). Click
“Settings” to produce an entire new set of tabs.  Then click “Device” to
show the dialog for choosing the sound card input and output devices to be used.
This dialog can also be used to determine the maximum sample rate and resolution
the sound device is capable of.  OK the selection and then click the “On”
button to start the scope and spectrum analyzer.

You should get a display something like the picture
above, depending on your input signals.  The spectrum analyzer (lower black
window), automatically runs in parallel with the oscilloscope waveform view in
the upper black window to produce two views of the same signal.

In the screen cap, Visual Analyzer’s own
audio generator has been set to create a saw-tooth wave form. A  software
“virtual cable”
was used to loop the generator’s audio output back into the audio
input for the scope and analyzer to yield the scope and analyzer display.  This would be the same as using a
3.5mm-to-3.5mm patch cord to connect the audio output of an actual sound card
back into it’s own Mic or Line input.   With a stereo input sound
device , Visual Analyser will function as a dual-trace scope. 

(Note that nearly all Mic-In jacks on PC
sound systems are monophonic; you must have a device with the “Line-In” third
jack, usually colored blue, to use the dual-trace feature.) 

The controls for the A & B channels of the scope can be
seen in the upper-right corner of the panel. The vertical bar graph indicators
shows input in dB, relative to the maximum input level the sound card can handle
without clipping distortion. I.e. where the soundcard’s analog-to-digital
converter maxes out at the largest numerical value it can produce (216
power for the typical “16-bit” sound card).

Any waveform, other than a pure sine wave, contains a
series of harmonics (integer multiples of the original a.k.a. “fundamental” frequency). The
relative levels of various harmonics depends on the shape of the non-sine
waveform.  In the screen shot above, the spectrum analyzer is clearly
showing the 1KHz fundamental frequency.  The 2nd, 3rd, 4th, 5th and beyond
harmonics of 1Khz are also clearly visible.

To the right of the spectrum analyzer window, circled in
red are checkboxes to turn on and display some of the other instruments. They
pop up in free floating windows as shown below.

The top image below is the audio generator. Note that
with a stereo output system, you can generate two completely separate outputs at
the same time.  I.e. you can use the left and right channels independently.

The middle instrument is an audio voltmeter capable of
reading either RMS or peak AC levels of signals applied to the sound card. The
maximum value that can be read will depend on the input signal handling range of
your particular sound card; usually a max of 1 or 2 volts peak-to-peak. 
DO NOT attempt to look at AC powerline waveforms or similar
higher-voltage signals — your sound card (and possibly the entire PC
motherboard) will be vaporized instantly!!!

The bottom window is an audio frequency counter that
will display the dominant frequency in an incoming audio signal.  This can
be used to read sub-audible tone squelch frequencies (a.k.a. “PL” or “CTCSS”
tones) for mobile radio systems off-the-air. You will need a wide-band
connection to the radio receiver.  The radio’s  discriminator output
(sometimes labeled “9600 baud RX”) at the 6-pin mini-DIN data port is an ideal
point for this kind of measurement. On most radios, the speaker-out jack will
not pass enough of these “sub-audible” tones to be read.  

[Complete details on the 6-pin Mini-DIN data
port, including pin-outs, are here on my website:
6-Pin-MiniDin-Data-Connector ]

This is only a fraction of what
Visual Analyser can do. 
Download this amazing piece of freeware and start playing with it!