Contents

About Audio Lab

Menus:

File Menu

Edit Menu

Wave Menu

Effects Menu

Tools Menu

Options Menu

Glossary


File Menu

The File Menu is very similar to other Windows applications and contains the usual  commands for manipulating files (New, Open, Save, Save As, and Quit). Audio Lab can load and save 8 bit resolution mono WaveAudio (.WAV extension) and Creative Labs  (.VOC extension) files.

Common Dialog boxes are used for the Open and Save As menu  items, and their operation is the same as in any other application which uses them.

Audio Lab supports Drag-and-Drop from the File Manager, and attempt to load any  .WAV or .VOC file that is dragged using the mouse from the File Manager and dropped  into Audio Lab. (See the Microsoft Windows User's Guide).


Edit Menu

The Edit Menu contains several standard Edit commands (Cut, Copy, Paste, Select All,  Clear), but the rest are specific to Audio Lab. These menu items are only available during  certain circumstances, described below:

Cut Unmarked Areas: When a block is marked, everything outside the block is removed  using this command.

Paste Mix: After a block of samples has been cut or copied, it is possible to mix the block  into a waveform at another position, with the result that both sounds can be heard  simultaneously. A Dialog Box will appear asking for the proportion of sound to be 'mixed  in' to the waveform.

Paste RingMod: Multiplies samples by the samples that have previously been cut (the same as a ring modulator). This gives a 'science-fiction' or 'robotic' effect depending on what samples are used. Sine waves (or similar, such as a sampled whistle) are recommended, and the effect is often used on speech waveforms. It could also be used to make someone's voice unrecognizable. Both waveforms must be loud, or the resulting waveform will tend to be very quiet.

Repeat Marked Block: This command makes space in the waveform equivalent to the  size of the marked block of samples, and then pastes the marked block of samples into that  position.

Set Marked Block: Opens a Dialog Box that allows the exact edges of the marked block  to be specified. If a block has been marked before this menu item is chosen, the edges of  the current marked block will be shown in the dialog box.


Wave Menu

The Wave Menu gives control over the playback and recording of waveforms, with menu  items having the same effect as their namesakes on a tape recorder, for example. The  Media Controller menu item will open the Media Controller, a special window that shows  a view of what is currently being played or recorded.


Effects Menu

This menu contains options that perform special effects on the waveform.

Reverse: Reverses the order of the samples in the waveform. This has the same effects as  playing a record or cassette tape backwards. Reversing a reversed sound puts the samples  back in their original order.

Invert: Turns the waveform 'upside down'. Like reverse, inverting a waveform twice gives  the original waveform. This is useful for stereo recordings, where it is often possible to  cancel the vocals in the recording by inverting one of the channels.

Volume Ramp: This menu item creates a dialog box that allows you to specify an upper  and a lower volume that will be 'faded' between. This effect is identical to turning the  volume on an amplifer from one setting to another over a period of time.

Silence: Changes all sample values to zero, which represents silence. This is useful for  'silencing' background noise between sounds, such as between sentences where someone is  speaking, or between musical performances.

Echo: This effect simulates an echo. The Dialog Box used to specify the echo contains 3  main controls.

1. Echo Amount - the volume of the echo, on a scale relative to the original sound  of 0 to 100.

2. Delay Time - the time before the echo is heard, in thousandths of a second. The time before the human ear can detect a distinct echo is around 20 milliseconds. Any echoes of this duration simulate effects such as making a single vocal track sound like a 'chorus'. Several echoes in the range of 20-100 milliseconds, with different amplitudes, can be used to create reverberation, to give 'dry' sounding waveforms more ambience.

3. Feedback - specifies whether the echo will occur only once, or whether the first  echo will be echoed itself repeatedly until the end of the waveform or marked  block. This is useful for creating effects where a sound keeps 'reflecting' off the  sides of a cave (for example), gradually fading away.

Ring Modulate: This effect is done by multiplying each sample by itself. The result of this  is that the frequency content of the waveform is changed so that it contains the sum and  difference frequencies of all the frequencies in the original waveform.

Example: If a waveform contains sine waves of frequency 800 Hz and 700 Hz, ring modulation will replace the waveform with one containing (800 - 700) = 100 Hz and (800 + 700) = 1500 Hz.

Spectrum Invert: The frequency-domain relative of the Reverse effect. This effect inverts the spectrum of the waveform, so that low frequencies become high frequencies, and vice-versa.

Example: A waveform of a 1 kHz sine wave sampled at 10 kHz  would be replaced by a sine wave of 9 kHz. This effect often produces odd-sounding results that are not really useful, such as the inverted spectrum of speech. However, it does have applications in creating new sound effects or instruments and the most 'interesting' results come from using these types of waveforms with this effect.


Tools Menu

This menu has options that are useful for manipulating the sound.

Sampling Rate: Changes the speed at which the sound is played back or recorded. All  waveform-audio devices have a fixed upper and lower limit on the sampling rate. When the  sampling rate is changed, the pitch of the waveform is changed proportionally.

Set Volume: Allows changing the volume of the waveform by multiplying each value in  the waveform by a constant. Note: If the volume is increased by too great an amount, the  waveform may be clipped, and hence sound distorted. Many volume changes over wide  ranges will eventually distort the waveform.

Max Volume: Increases the volume of the waveform to the maximum that is possible  before clipping occurs.

Noise Gate: Sets all samples below a specified volume to zero. This is an easy way of  silencing all sound below a certain volume, such as background noise between words and  sentences during speech. However, it will also have an effect on the 'wanted' part of the  waveform which will likely contain samples below the specifed volume. Recommended  values for reducing background noise are between 5 and 10 probably cause distortion, depending on the nature of the waveform.

Quantize: Reduces the dynamic range of the waveform. Each time the number of bits  specified is decreased by one, the dynamic range will decrease by approximately 6  decibels. This is useful when preparing sound to be compressed - quantizing the waveform  to the maximum desired level of background noise will produce the best compression.

Change Sign: Changes the waveform samples from the range -128 to + 127, to 0 to 255. This menu item is mainly useful when RAW waveform data has been loaded, but it sounds very badly distorted. Often the distortion is caused by the 'sign' of the waveform samples being incorrect.

Add Samples: Adds a number of samples to the waveform. If there is no marked block  specified, they will be added to the end of the waveform. If not, the samples will be  inserted at the left-most edge of the marked block.


Options Menu

This menu lets you choose input and output (recording and playback) devices that will be  used by Audio Lab. The name of each waveform-audio device (as reported by its Windows  driver) can be selected, and the capabilities of each device can be seen in the Dialog Box. If there are no sound drivers installed, the only option will be to choose "(none)".


Glossary

Background Noise: A low-level 'hiss' sound that is present in all digitised waveforms to some  extent, which is caused by Quantization Error. Using a higher resolution to store the file minimises  background noise at the expense of increased storage space. If the resolution is decreased by too  much, the background noise will increase until it is heard as distortion.

Clipping: Distortion caused by sample values being calculated that are too high or too low to be  stored. These are 'clipped' to the highest or lowest value, respectively, before being stored. Unlike  clipping caused by overloading an amplifier, clipping in digital audio cannot cause damage.

Digitising: See Recording.

Dynamic Range: See Resolution.

Files: A waveform stored on the hard disk of the computer. There are two methods of loading and  saving files with Audio Lab: WAV files and VOC files. The only difference is that WAV files are  structure better than VOC files, and are the standard for use with Microsoft Windows Multimedia  products. New files should generally be stored in WAV format.

Frequency: Roughly corresponds to the pitch of a sound. Low-frequency sounds have lower pitch  than high-frequency sounds. A waveform is usually made up of several frequencies combined.

Playback: Playing back each sample stored in a waveform, one after the other, at a certain  sampling rate.

Quantization Error: The error introduced into a waveform when it is digitized. Higher-resolution  samples have smaller quantization error, because they have a larger range of numbers that can be  used to approximate to the original waveform.

Recording: Converting a sound into a digital waveform stored in the computer, via a Waveform-Input device such as a Soundblaster sound card attached to a microphone.

Resolution: The resolution of a sample determines the accuracy of a sample. There are two main  resolutions - 8 bit and 16 bit. 8 bit samples approximate voltages to an integer value between 0 and  255, while 16 bit samples approximate voltages to a value of between 0 and 65,535. 16 bit samples  are used to store high-quality music (e.g. Compact Disks), and are capable of storing waveforms  255 times more accurately than 8 bit samples, while only using twice the storage space.

Sample: A number that represents the voltage of a waveform at a precise instant. Samples have  resolution (the accuracy with which they can store samples) and size, which increases with  resolution.

Sampling Rate: The speed at which samples are recorded or replayed. This is measured in Hertz or  KiloHertz and typical values are between 4,000 Hz (samples per second) and 44,100Hz (the  sampling rate used by Compact Disks). Higher sampling rates correspond to higher quality and  greater storage space. Also, it is impossible for a waveform stored at a certain sampling rate to  contain a frequency of greater than half of that sampling rate.

VOC File: See Files.

WAV File: See Files.

Waveform: A sequence of samples, one after the other, that are played back or recorded at a  certain sampling rate to make up a sound. The higher the samping rate, the faster the waveform will be played back.


About
About Audio Lab

Audio Lab V1.1D

Copyright (C) 1994 Hamish Hubbard

All Rights Reseved

Audio Lab is a digitised sound editing program that runs under Windows 3.1. It graphically displays waveforms representing sounds that can be recorded (with the appropriate hardware) or loaded from disk, processed, and then saved again. Using these displays, cut and paste operations can be done on the waveform and special effects such as echo and fading in/out can be applied.

Thanks to Borland International (N.Z.) Ltd for their donation of Borland C++ which was used to write this program for entry into the New Zealand Software Awards. This program won the Under-18 division.

Hardware requirements:

A Windows 3.1 / OS/2 2.1 compatible computer, preferably running in 386 Enhanced mode

with virtual memory enabled.

A VGA-compatible (or better) graphics adaptor.

Mouse or other pointing device.

Approximately 850k of free hard disk space.

A sound card that can support waveform audio through a Windows 3.1 driver is recommended.

A driver is included that is compatible with the internal speaker (playback only).

Software requirements:

Windows 3.1 or OS/2 2.1 with Win-OS/2 installed.

E-mail:

Hamish_Hubbard@kcbbs.gen.nz

Enigma BBS: +64-9-480-0931

Powerlink BBS: +64-9-525-5492