ADI-96 PRO Audio Analyser Online Help Version 1.0

Contents

  Brief Description and Characteristics
  Hotkeys
  Software Audio Analyser
      Overview
      Settings Spectrum Analyser
  Notes on Operation


Brief Description and Characteristics

The DSP software Audio Analyser transforms the ADI-96 PRO into a powerful Spectrum Analyser. As opposed to nearly all current PC based solutions no FFT (Fast Fourier Transform) is used. Although this method needs only little calculation (CPU) power, it offers no useable translation of sound in vision. The 'bands' of a FFT have a constant frequency distance, which results in the higher area in numerous bands, but in the lower frequencies in only some bands. Some manufacturers try to minimize this behaviour, but even then a sine will show an un-symmetrical display and an insufficient band separation.

The DSP of the ADI-96 PRO performes a real bandpass filter calculation, as usual in all professional 'Audio Spectrum Analyzers'. The distance between the filters is not linear, but scaled according to human hearing. Thanks to the external calculations the BeOS software does only display the results. This allows to run a 30 band Analyser with 50 dB range, sharp filters and 100 LED's per band even on an older PC, without driving the computer to its limits.

Thanks to its complete digital operation the Audio Analyser offers features previous unavailable from analog Analysers. These features include freely adjustable attack and release time, a display configurable in many ways, different filters and special display modes. Because of its high-quality AD-conversion the ADI-96 PRO offers its Audio Analyser will precisely show levels down to -120 dB.

Please note that the ADI-96 PRO will operate as high end Mic/Line AD-converter even in Audio Analyser mode! But the functions provided by the 'Dual Mono A/D' software (Low Cut, Delay, Expander, De-esser, NLC, ALC) are not available in Analyser mode.


Hotkeys

Some functions are directly accessible using predefined shortcuts:

Left L
Right R
L+R (Mono) M
Freeze Space
RMS/Peak Meter D

Furthermore there's direct access to the following menu entries:

Help - Contents        F1
Analyser Settings     F2

The keys F5 to F8 offer a fast switch function between four different setups. The setups can be changed anytime, as they consist of the four (supplied) files fastkey5.a96 through fastkey8.a96. Load the according setup using the menu's entry File/Open Setup File, change the settings to your needs. Then store the settings using Save Setup File, but don't change the name! Those four files must reside in the same directory as the main program ana96.x86.


Audio Analyser - Overview

First Usage
Connect the COM-port of your BeOS PC and the RS-232 interface of the ADI-96 PRO using the supplied D-type 9-pin cable. Use 'Boot other function' at the ADI-96 PRO to boot the DSP software 'Audio Analyser'. Start the BeOS software ana96.x86 and check the currently used port (COM1/COM2).

Operation/Settings
The visualization on the screen is not mainly set by the ADI-96 PRO, but by the BeOS software. That's why only some parameters are directly configurable at the device. After starting the software use F2 or the right mouse key to open the window 'Analyser Settings'. Here all parameters can be adjusted in a convenient way. The guidelines of using Remote Control (see manual) are the same for this software.

Analyser Settings
The window Analyser Settings includes four function areas:

INPUT
Choice of input (Mic, Mic phantom powered, Line) per channel, invert phase (180°) per channel, activation of M/S processing. See manual section 7.1.

SPECTRUM ANALYSER
Holds all parameters controlling the display of the audio signal in the analyser window. Additional the display modes are set.

LEVEL M.
Activation of display and configuration of the the RMS/Peak Level meter: Peak Hold Time 0,1 s to 9,9 s, Release 1 dB/s to 100 dB/s

OUTPUT
Configuration of the signal at the digital output: Sample frequency, word length, Dither, word clock and Channel Status. See manual section 7.2.

Storing / Loading / Editing of Setups
The software allows to store, load and edit setups from and to the PC's storage media. No setups will be stored to or loaded from the ADI-96 PRO.


Settings Spectrum Analyser

Type
Number and Quality factor of displayed bands. Available are:

  10 band (1/1 oct. steps), Quality factor 1,4 or 2,5
  15 band (2/3 oct. steps), Quality factor 1,4 or 3
  20 band (1/2 oct. steps), Quality factor 3 or 5
  30 band (1/3 oct. steps), Quality factor 3 or 5

The width of the display window is automatically adjusted to the number of of bands. The values printed on the x-axis are rounded for better readability. At a sample rate of 32 kHz the band 20 kHz isn't available, as no frequencies above 16 kHz are sampled. The choice of Quality factor defines the crosstalk between the bands.

Source
Sets the channel to be displayed. Adjustable to left, right, left plus right (monaural) and left minus right (only stereo).

Rise Time
Rise time of the display, adjustable from 0 ms to 200 ms. Values below 5 ms lead to a display even of shortest peaks. Values around 7 ms will lead to a display which behaves more like the audio heard. Values greater than 30 ms result in a display similar to a VU meter.

Release
Release time of the display, referenced to 20 dB. Adjustable from 0,3 s to 20 s. A good readable display is achieved at around 2 seconds. When measuring using noise signals 20 seconds result in a smooth and well readable display.

Hold Time
Hold time of the optional peak level meter (mode Peak Hold), adjustable from 0,1 s to 9,9 s.

Range
Visible display range. Choose between 30 dB and 50 dB.

Top Level
Highest level displayed in the analyser window. Serves to adapt the display to the actual signal level. Available settings are 0 up to -70 dB in steps of 10 dB.

Mode
Kind of display. Bar shows a solid bar, Point only one LED/segment per band. Peak Hold combines bar and peak display. The peak portion is defined by Hold Time.

Size
Size of the analyser window. Choose between small, medium and big.

Resolution
Range in dB per LED/segment. Choose between 0,5 dB, 1 dB and 2 dB.

Instant Hold
Sets the release time in Bar and Point mode to infinite. In mode Peak Hold only the peak display will be set to infinite release.

Reset
Resets all peak values covered by Hold Time or Instant Hold.

Freeze
Freezes the display to the current state. Snap shot function.


Notes on Operation

The most important application using a Spectrum Analyser is the visualization of frequencies and levels found in music or speech. What you see is what your hear! The Analyser shows levels and frequencies even at the edge of the human ear's abilities. The visual display helps to train your ears, and avoids serious mistakes when mixing to the master tape. Usual studio monitors won't let you hear frequencies below 100 Hz. Simply look on the Audio Analyser to see what's going on in the underground!

Reading the display is not easy for novices because of the huge amount of information it shows. But after some training you'll agree that this tool is a precious help in every day work.

Analysis of Music
Attack and Release time are the most important parameters when trying to achieve a display similar to what you hear. At a very fast attack setting the Analyser will show even shortest peaks down to one sample. But these are only audible when present in several bands and lasting for more than a millisecond. That's why 7 ms Rise Time results in a much better display behaviour. The release time should be set to three different values. A very fast display (1 s) is recommended for example when trying to see the bass which normally hides behind the bass drum. At 2 s the display will be more easier to read and is more friendly to your eyes. Some special applications (like averaging the sound impression or noise measurements) require values around 10 to 20 seconds.

Special Display Modes
The Audio Analyser offers two different envelope modes. Let's look at this example: You want to study the frequency distribution of a bass drum sample.

Method 1: Route the bass drum sample to the Analyser and store the display's contents by hitting Freeze in the right moment. Much more convenient is

Method 2: Use Instant Hold to activate the envelope mode. Play the bass drum sample one time. Thanks to the infinite release time the analyser's result won't vanish from the screen.

Method 3 is mainly used with music. At active Instant Hold and display mode Peak Hold the music is shown as usual, but the peak display above the bars won't be reset. When playing back a 3 minute Pop song an envelope of all frequencies and levels which occured is shown.

Sound Measurements
The combination Equalizer/Analyser is used to correct the misalignment of speakers and room. A test signal (pink noise) is send from the speakers into a special measurement microphone placed at the engineer's preferred listening position. At a release time of 20 seconds, Riste Time 200 ms and active Point mode a display of the overall frequency response is shown. The external Equalizer is now used to correct this curve to a straight line.

Special Applications
At the highest display range (50 dB) and lowest Top Level setting (-70 dB) the Analyser displays all signals down to -120 dBFS. This allows to examine the hum and noise present in the studio's environment. Disturbing frequencies can be classified and removed more exactly. In Left minus Right mode only the stereo signals of a complete mix are shown. This gives some interesting information on the mixing technique.