
            Digital Function Generator for NeXTSTEP
           Real Time Sine Generator -Demo Version 1.4,  June  1994

                           Copyright  1993-1994,   DIGITAL  RECORDINGS,   All Rights Reserved

                                                            Topics covered

                            ** Installation Instructions
**.......................................................
                         General  Information
............................................................................
                               Use  of  DFG  in  Teaching  and  Research
....................................
                            Software  Specifications /
Parameters.............................................
                            DFG
Modules.........................................................................................
                            How  to  use  the  DFG_P Module
....................................................
                            Variables and Buttons used in the
Software...................................
                               General Information about Digital Recordings
.............................
                               Software for NeXTSTEP developed at Digital Recordings ......
                            Your  Satisfaction  and  Your
Suggestions......................................
                            More
Information..................................................................................

Warning: Please decrease  Volume  on  NeXTSTEP Computer  (or  on  external amplifier) to
avoid  damage  to  speakers  or  your  hearing !

**  Installation  Instructions  **

7       Copy DFG_RT file to the directory of choice (eg.  Apps ).
7       Read  this Help  file  for further information about DFG and how to use it.


General  Information 

DFG_RT module was written for real-time synthesis of the sinusoidal
(pure tone) signal.  Signals are generated in real time and do not
require the DSP processor (which is not available in some NeXTSTEP
computers). Therefore this software will run on all NeXTSTEP computers
equipped in D/A converters.  Signal is generated in RAM and for this
reason no hard disk space is required for operation of the DFG_RT
program.  This program works very nicely with Digital  Oscilloscope
and Spectrum Analyzer (both applications come with NeXT) and any
recording / editing software.  Playback and recording/analysis of
the signal could be done simultaneously since DSP chip is not used
and main processor is used only 2->3% during signal production.

The Digital Function Generator (DFG) software has been developed
under NeXTSTEP Release 3.2 by DIGITAL  RECORDINGS - Advanced R & D,
Halifax, Nova Scotia, Canada. It works on Motorola and Intel - based
NeXTSTEP computers with NeXTSTEP-supported D/A converters. Soon it
will be also available for Sun and HP computers running NeXTSTEP.

The DFG / NeXT combination is a powerful tool for generating arbitrary
sounds of arbitrary complexity and ultimate quality. Since DFG does
not use DSP resources (Motorola 56001 chip) and since it uses only
2-3% of the CPU time, it can run simultaneously with such applications
as  the Digital  Oscilloscope  and Spectrum  Analyzer (both
applications come with NeXT). Therefore, the single DFG/NeXT
combination can be used to perform sophisticated tests and
experiments, since it can synthesize and analyze signals at the same
time. The DFG is an ideal signal source for many applications in
the field of acoustics, psychoacoustics, physics, architecture,
audiology, electronics, electroacoustics, vibration measurements
and transducer testing.


Use  of  DFG  in  Teaching  and  Research

In the past  DFG software has been used successfully  in various
research and projects and in the teaching of various courses related
to acoustics, psychoacoustics, hearing aids, instrumentation,
electronics, audiology and speech pathology.

In particular, the Principles of Digital Audio module, illustrated
by this demo,  has been used to generate  pure tones and white noise,
to illustrate concepts of signal amplitude, frequency, phase,
interference, coherence, incoherence, signal ramping, beats and
virtual pitch. Also, it has been used to demonstrate quantization,
dithering, aliasing / hard clipping / harmonic/ intermodulation
distortions, etc.

Students generated signals according to parameters input through
the Graphical User Interface and listened to these signals via
headphones or an amplifier with a set of speakers.  The A/D64x
Interface from Singular Solutions was used to input the generated
signal back to the NeXT computer, so the signal could then be
displayed on the Oscilloscope and Spectrum Analyzer. The same
interface was used to digitally transfer generated test signals to
a DAT (Digital Audio Tape) recorder. These recordings were used in
various experiments conducted in electronic and acoustical labs.

The quality of signals generated with DFG is higher than the quality
of signals available on most test CDs. Also, DFG can generate a much
wider variety of test signals than are available on CDs. This proved
to be very helpful in both teaching and research.

Teachers' and students' satisfaction with DFG has been very high.
Concepts which have often been difficult or even impossible to
demonstrate with standard equipment, can now be easily demonstrated,
both acoustically and visually, with the DFG/NeXT/A/D64x combination.
This dramatically increased the speed of learning and the level of
understanding.

Users' remarks about DFG Software :

We have been using the DFG software on a NeXT computer both for
doing research and for teaching.  DFG has proved to be an excellent
companion to courses on acoustics and psychoacoustics.  Teachers in
our department have used the software for generating stimuli to
demonstrate hearing phenomena to students in our classes.  In
addition, DFG's user-friendly visual interface has enabled our
students to have 'hands-on" experience of acoustics and digital
signal processing concepts without having to spend a lot of time
learning about digital sound synthesis.  In my research, I have used
the DFG modules to generate stimuli for running psychoacoustics and
auditory pattern perception experiments.

Dr. Valter Ciocca
Dept. of Speech & Hearing Sciences
University of Hong Kong, Hong Kong


The five modules of Digital Function Generator are excellent sound
sources for digital synthesis on the NeXT workstation. For the
generation of pure tones in arbitrary and/or complex situations
these programs are fast, efficient and easy to use. I have used them
extensively in combination with such standard NeXT sound programs
as Paul Lansky's cmix and realtime and SoundWorks from Metaresearch.
As a composer, I feel my suite of NeXT software tools greatly enhanced
with them not only in contributing to my composing, but in what I
have learned about tone generation and architecture through analysis
of their results.  The interfaces of the five DFG modules are also
among the best I have seen among all NeXTSTEP software I have
auditioned. I found tech support from Digital Recordings to be fast,
efficient and thorough. I recommend Digital Function Generator highly
to any composer seriously working in a NeXTSTEP environment.

Charles Dvorak, composer
Pacific Palisades, California, USA


Digital Function Generator software is available for over one year
in the Sound Engineering Dept. of the Technical University of Gdansk.
It has been  widely  used in the following laboratories:
o       Laboratory of Principles of Digital Technology,   
o       Laboratory of Psychophysiology of Hearing, 
o       Laboratory of Musical Acoustics, 
o       Laboratory of Sound Synthesis Methods. 
I found this software exceptionally flexible. It was conceived in
such a way that it is possible to use it to both:  to demonstrate
principles of digitally generated sound  and to replace many
standalone devices used as a standard equipment of sound engineering
laboratories. The first mentioned feature is particularly useful in
the Laboratory of Principles of Digital Technology. The DFG is the
first commercially available tool for the demonstration and explaining
the dither effect and its influence on the quality of low-bit
quantized audio. Using this feature students may observe the
dependence of subjective quality of generated waves on the dither
presence and parameters.  The capability of producing almost any
wave using additive synthesis module is widely exploited in the
Laboratory of Psychophysiology of Hearing. The software is applied
to demonstration of the bits perception, the masking effect, the
threshold of hearing, the threshold of nonlinear distortion
perception, the dynamic scale of hearing sense and many others.
Hitherto, I was compelled to use 5 or 6 heavy and expensive standalone
devices. Now, I have direct access to all such functions and I feel
not constrained by the necessity to reconfigure the hardware layout
during the experiments.  The sound synthesis is also the basic tool
used to the Laboratory of Sound Synthesis Methods. Once again the
flexibility of the software is applicable to the generation of
diversified signal patterns.

The exceptional quality of the NeXT audio channel being clever
exploited by the software allows for producing sound patterns having
very high resolution. Consequently, the NeXT work-station provided
with the DFG software is becoming step by step the main device in
our laboratories. Presently, we use this platform for almost every
subjective or objective testing in the domain of pure tones or
synthetic waves.

Bozena Kostek, Ph.D., P. Eng. 
Sound Engineering Dept., Faculty of  Electronics
Technical University of  Gdansk, Gdansk, Poland


Software  Specifications / Parameters 

Stereo output - different waveforms can be synthesized in two independent channels. 

Frequency adjustable continuously from 0 to 20,000 Hz.

Frequency stability +/- 0.0001 Hz (accuracy of the quartz clock).

Amplitude adjustable continuously from -140 to  0 dB  or from 0 to 32,767.

Phase adjustable continuously from 0 to 360 degrees.

S/N ratio = 95 dB (with dither).

No harmonic and no intermodulation distortion.

DFG does not use DSP resources (Motorola DSP 56001 processor),
therefore the DFG, Digital Oscilloscope and Spectrum Analyzer can
run simultaneously.

The simultaneous playback of sound by DFG and the recording of this
sound via microphone input  or the stereo  A/D interface (from
Singular Solutions, Ariel or MetaResearch) allows for very flexible
testing and experimental procedures.

Generated sounds are written to standard stereo, linear 16-bit
soundfiles (*.snd). These files can be used in other sound
applications such as sound editors. Complex sounds can be saved for
fast retrieval and playback.

Available Signals: sine wave, square wave, triangular wave, sawtooth
wave, pulse, white noise, AM, FM and AFM modulation, frequency sweep,
amplitude sweep, amplitude plus frequency sweep, additive synthesis,
etc.


DFG  Modules

The Digital Function Generator software consists of five modules:

Principles of Digital Audio - for generating  pure tones and white
noise, to illustrate concepts of signal amplitude, frequency, phase,
interference, coherence, incoherence, signal ramping, additive
synthesis, beats, virtual pitch as well as  to demonstrate
quantization, dithering, aliasing / hard clipping / harmonic /
intermodulation  distortions, etc.

Modulation (AM, FM, AFM) - for generating amplitude modulated tones
(AM), frequency modulated tones (FM) and amplitude plus frequency
modulated tones (AFM).

Additive Synthesis - for generating complex sounds synthesized from
their Fourier components.  Amplitude,  Frequency and Phase of each
stereo component is adjustable continuously.

Sweep Generator (AS, FS & AFS) - for generating linear, logarithmic,
up or down types of amplitude sweeps (AS), frequency sweeps (FS)
and amplitude plus frequency sweeps (AFS).

Function Generator - for generating waves such as sine, square,
triangular, sawtooth, pulse and to generate white noise.


How  to  use  the  DFG_RT  Module

Warning: Please decrease  Volume  on  NeXTSTEP Computer  (or  on
external amplifier) to  avoid  damage  to  speakers  or  your
hearing !

DFG software is intuitive to use and was designed with ergonomics
in mind. However, we recommend that you read the following
instructions before using the software.

7       To start the application, double click on DFG_RT icon.

7       Press "Play" button to produce signal.  This will play signal for 100 sec.

7       You can change any parameters on the DFG_RT screen to change parameters in real time.

7       Press "Stop" button to stop signal or wait for 100 sec and signal will be turned
"OFF".

7       More than one DFG_RT panel can be opened at the same time. One panel can produce one
signal while the other is producing another signal. This is useful during demonstrations.


Variables  and  Buttons  Used  in  the  Software
 
The following is a short description of variables and buttons used in the software :

The L channel / L+R/ R channel switch allows signal to be synthesized in L, R or both channels
at once. This could be changed in real time during playback.

Frequency is any integer number from 1 to 20,000 and represents the
frequency of the signal in Hz. Please avoid loud levels when listening
through the built-in speaker, since it can cause damage to it.
Practical range for this speaker is from 100 Hz to 15,000 Hz. For
best results use headphones or an external amplifier and speakers.
Frequency could be changed in real time during playback by using
provided buttons or by direct number entry in the window. This method
is more reliable than slider.  Please note - in DFG_RTdemo version
frequency is limited to 200 Hz to 2000 Hz.
	
Dither is added to all signals to eliminate the harmonic and
intermodulation distortion generated in typical generators.

Amplitude of signal is adjusted to maximum to provide S/N = 95 dB
(with good D/A converters).


General Information about Digital Recordings and our products

Digital Recordings is a small High-Tech company formed in 1985. Our company is primarily
involved in the following Services / Consulting / Research areas :

o    Advanced Research and Development in Acoustics
o    Digital & Analog Sound Recording and Editing
o    Digital Signal and Sound Processing (DSP & DSdP)
o    Audio / Acoustical Consulting & Systems Design
o    Computerized Data Acquisition & Systems Design
o    Software and Hardware Development for NeXTSTEP 
         (we are Registered NeXTSTEP Developer)

Inventions / New Techniques / Novel Products / Scientific Contributions :

o    DCC High-Precision Time of Flight Method
o    Ultrasonic Computerized Tomography Scanner
o    Tomographic Thermal-Wave Scanner
o    DSA (Digital Speech Aid) for stutterers
o    DFG (Digital Function Generator) Software
o    New theory on the origins of Life
 
We consider NeXTSTEP to be the best operating system on the market
today. Its features and object-oriented development environment lead
the industry. This is why we decided to develop software and hardware
products for the NeXTSTEP computers. Currently we are working on
many new products for NeXTSTEP in the area of sound and DSP. Below
is a short description of our commercial software product for
NeXTSTEP.

Our most recent research project is in the area of speech disorders.
We have developed a new, revolutionary electronic device called DSA
(Digital Speech Aid) for elimination of stuttering.  DSA works
similarly to the Hearing Aid and is in the process of being patented
internationally.


Software for NeXTSTEP developed at Digital Recordings

Digital Function Generator (DFG)

Product availability:         shipping now

The Digital Function Generator (DFG) software has been developed
under NeXTSTEP Release 3.2.  It runs under system 2.0 and 3.2 on
all types and configurations of NeXTSTEP computers. The DFG/NeXT
combination is a powerful tool for generating arbitrary, stereo
16-bit sounds of arbitrary complexity and ultimate quality.

DFG consists of 5 modules. The Principles of Digital Audio module
allows synthesis of pure tones and white noise and it can be used
to illustrate concepts of signal amplitude, frequency, phase,
interference, coherence, incoherence, signal ramping, additive
synthesis, beats, virtual pitch, quantization, dithering, aliasing
/ hard clipping / harmonic / intermodulation  distortions, etc.
The Modulation panel allows synthesis of Amplitude, Frequency or
Amplitude and Frequency Modulated tones. The Additive Synthesis
module allows synthesis of complex sounds from their Fourier
components. The Sweep Generator module is for producing arbitrary
amplitude, frequency or amplitude and frequency sweeps. The Function
Generator module can be used to synthesize sine, square, triangular,
sawtooth, pulse and white noise signals.

Since DFG does not use DSP resources (Motorola 56001 chip) and since
it uses only 2-3% of the CPU time, it can run simultaneously with
such applications as  the Digital  Oscilloscope  and Spectrum
Analyzer (both applications come with NeXT).  Therefore, the single
DFG/NeXT combination can be used to perform sophisticated tests and
experiments, since it can synthesize and analyze signals at the same
time.

DFG is an ideal signal source for research and teaching in the fields
of acoustics, psychoacoustics, physics, architecture, audiology,
electronics, electroacoustics, vibration measurements and transducer
testing. Academic discounts are available. A free demo version of
this software can be provided.


Digital Function Generator - Extended

Product availability:         June 1994

The Digital Function Generator -Extended (DFG_EX) software is being
developed under NeXTSTEP Release 3.2.  It runs under system 2.0 and
3.2 on all types and configurations of NeXTSTEP computers.

DFG_EX is a DFG-enhancing set of software modules for construction
and playback of arbitrary,stereo 16-bit sounds. Since DFG_EX does
not use DSP resources, it can run simultaneously with such
applications as the Digital  Oscilloscope and Spectrum Analyzer.
The current version of the DFG_EX software consists of 4 modules:

o    Sound Sequencer - for construction and playback of arbitrary sound sequences
o    File Editor / Mixer - for precise editing and mixing of sound files
o    Sound Presenter - for simultaneous and convenient playback of many sound files
o    An enhanced version of DFG Noise Generator, for generating noise with  uniform, 
     triangular, and gaussian PDF (Probability Density Function). 

DFG_EX is an ideal signal source for many teaching and research
applications in the fields of acoustics, psychoacoustics, physics,
audiology, electronics, electroacoustics, audio and vibration
measurements. Academic discounts are available.


Digital Psychoacoustic Laboratory

Product availability:         September 1994

The Digital Psychoacoustic Laboratory (DPL) software is being
developed under NeXTSTEP Release 3.2.  It runs under system 2.0 and
3.2 on all types and configurations of NeXTSTEP computers.

DPL is a DFG-enhancing set of software modules for performing
experiments related to psychoacoustics. It includes various
presentation panels for automatic testing of subject's responses.

Soundfiles produced by DFG (Digital Function Generator), DFG_EX
(Digital Function Generator-Extended) or other sound generating
applications are stored in a "Sound Box" folder, from which they
can be retrieved in sequence or in random order by the DPL software.
Subject's responses are recorded in a data file for later analysis.

DPL is an ideal tool for teaching and research in the fields of
acoustics, audio, psychoacoustics, neurology, audiology and speech
pathology. Academic discounts are available.


Digital Audiometer

Product availability:         December 1994

Digital Audiometer, software plus hardware, enables investigations
of threshold of hearing in the frequency range from 20 Hz to 20,000
Hz, with frequency resolution of 1Hz and amplitude resolution of
1dB. All standard tests are available. Moreover, some special hearing
evaluation procedures were implemented, which are seldom applied in
practice today due to technical problems. Various non-standard tests
are available for investigation of DLs (Difference Limens), temporal
resolution, etc. Digital Audiometer allows for an easy assessment
of intensity, frequency and temporal resolving capabilities of the
normal and impaired auditory systems.

Calibration of the audiometer is not required due to the stability
of the digital circuitry. This new audiometer allows for a more
accurate evaluation of hearing loss, auditory problems and
capabilities. It is particularly important for the new generation
of more advanced Digital and semi-Digital Hearing Aids.

Digital Audiometer is being developed under NeXTSTEP Release 3.2 in
collaboration with the Sound Engineering Department of the Technical
University of Gdansk, Gdansk, Poland. It runs under system 2.0 and
3.2 on all types and configurations of NeXTSTEP computers. Academic
discounts are available.


Digital Sound Restoration Laboratory

Product availability:         December 1994

Digital Sound Restoration Laboratory (DSR-Lab) is a NEXTSTEP 3.2
application designed for digital restoration of sound from old
records or magnetic tapes. An artificial intelligence learning
algorithm, based on neural networks, is used for the detection and
elimination of scratches and similar types of impulse noise. Another
artificial intelligence learning algorithm, implementing the Wiener
adaptive filtering procedures, is used for noise suppression.

The neural network approach, used in the DSR-Lab, brings a "human
touch" to the recognition of clicks and noise, because the training
process is based on a human perception. This in turn leads to an
obvious supremacy of the DSR-Lab algorithms over other methods that
exist today for the detection of impulse sounds and noise in the
old recordings. Also, the processing speed achieved with the DSR-Lab
algorithms is much higher than with other algorithms.

The DSR-Lab application is being developed under NeXTSTEP Release
3.2 in collaboration with Sound Engineering Department of the
Technical University of Gdansk, Gdansk, Poland. Academic discounts
are available.


ASCII File Filter

Product availability:         shipping now

The ASCII_Filter program was written for filtering out of the
non-ASCII characters from ASCII files. Transmission  errors, wrongly
entered characters, etc., are only a few reasons for non-ASCII
characters making their ways into ASCII files. Tasks such as Kermit
file transfer, transfer of files from one application to another
and compiling corrupted source code often results in errors when
such corrupted files are involved. Since standard editors will not
display some of these characters, detecting them becomes not an easy
task.

Second application of the ASCII_Filter program is a conversion of
ASCII files and non-ASCII files between different platforms. The
following conversions are currently possible: DOS->Mac, DOS->UNIX,
UNIX->Mac and Mac->UNIX.

Third application of the ASCII_Filter program is an exchange of
arbitrary characters (decimal value 0->255) in the ASCII or non-ASCII
file into arbitrary characters (decimal value 0->255). ASCII_Filter
displays also the number of characters of given type and the total
number of characters in the input file.


TOP SECRET

Product availability:         June 1994

TOP_SECRET software is being developed to protect privacy of
communication between people doing research and classified work.
NeXTmail and other types of communication software can be used with
encrypted files. TOP_SECRET can be also used for encryption of
confidential files on the hard disk in order to protect them from
unauthorized access.

TOP_SECRET works on all types of files. Level of protection is
adjustable. For increased security one can use several different
keys in order to "open" a file. Each key could be in hands of a
different person. Loss of one or several keys will not jeopardize
security of protected files. Keys and algorithms could be changed
and modified in order to customize TOP_SECRET for a particular
application and level of security.

TOP_SECRET is based on the latest algorithms in the Chaos Theory.
For all practical purposes probability of unauthorized decoding of
encrypted information is equal to 0. Academic discounts are available.


Your Feedback on DFG_RT

We hope that you will find this program useful. It provides at low
cost very high quality real-time generator, which could be used in
teaching and reasearch in the fields of physics, acoustics,
electronics, audio engineering, mechanics etc.

We are looking forward to your feedback regarding the use and
improvements of this program.  All suggestions regarding the DFG_RT
software and its use will be greatly appreciated.

Please feel free to use and to distribute DFG_RTdemo software to
other NeXTSTEP users.


More  Information

For more information about the DFG_RT software and other products and how to order them 
please contact:

        DIGITAL  RECORDINGS - Advanced R & D    5959   Spring  Garden   Road,   Suite 1103
        Halifax, Nova  Scotia  B3H - 1Y5, Canada

        Tel. / Fax.            (902) 429-9622
        E-mail :            mmieszko@ac.dal.ca

 

