DG1: Audio 2

PEAKS GLOSSARY

AIFF
Apple's Audio Interchange File Format used for recording and storing digital audio.It is also Peak 's default file format and is supported by many Macintosh software applications.
AUDIO CARD (third-party audio card, audio expansion card; audio recording/playback card)
A third-party expansion card that plus into a NuBus or PCI or PCMCIA slot in your Macintosh. These cards enhance a computer's audio recording and playback capabilities.
BIT RESOLUTION (BIT RATE)
Describes how many bits -as in "0s " and "1s "-are available to describe a digital recording.In practice, the bit resolution defines the dynamic range of a sound, whereas the sample rate defines the frequency range. 16-bit audio is the professional Compact Disc standard; 8-bit audio is suitable for less demanding applications, such as multimedia presentations. More bits result in better quality, but also require more hard drive storage space. Also refer to dynamic range, frequency,and sample rate.
CLIPPING
A type of audio distortion that occurs when a source signal (such as >from an audio CD player) is recorded at such a high level that the recording device (such as a Macintosh running Peak) runs out of "headroom." It can also occur when a signal is played back from a audio source into an audio destination at an excessive level, such as when a mixing console feeds a signal to a power amplifier at an extremely high level. In either case, clipping represents a mismatch in level between an audio source and an audio destination. When digital clipping occurs, such as during digital recording, the results can be a harsh "crackling" or "raspy" sound.
dB (decibel)
This is the most common unit used for measuring the level of audio. The greater the number of decibels, the higher the audio signal. Within Peak, the record and playback meters show a signal's relative level in terms of dB. There are many different kinds of decibel scales, but for the purposes of using Peak,"dB" can be used to describe the relative gain of different passages of audio, or to describe the available headroom during recording. Also refer to gain and headroom.
DSP
DSP stands for digital signal processing. In the world of audio, DSP refers to manipulating a digital audio signal by processes such as level changes, reverberation, delay,  or other such effects. Peak uses DSP to perform many of its audio processing tasks -including those found in the DSP menu or Toolbar.
DYNAMIC RANGE
In audio recording terminology, dynamic range refers to the range in level between the quietest and loudest passages of a selection of audio. It is usually expressed in decibels. Bit resolution determines a recording 's dynamic range. An 8-bit recording has 256 available levels, which translates into a dynamic range of 48dB. This may be suitable for some applications, but it may also sound noisy, since the difference in gain between the loudest passages and the quietest passages (which may contain hiss and other potential noise) is not that great. A 16-bit recording has 65,536 available levels, which translates into a high-quality dynamic range of 96dB. As a rule of thumb, you can calculate dynamic range in decibels by multiplying the bit rate by "6." Also refer to bit resolution, decibel, and gain.
FADE-IN/FADE-OUT
A fade-in is a process where the gain of an audio signal is increased from zero (silence) to its full volume. A fade-out is a process where the gain of an audio signal is decreased from its full volume to zero (silence).
FREQUENCY
Sound consists of waves, which occur in cycles. Frequency refers to how frequently these wave cycles occur in a given period of time (generally, one second). The higher the frequency of a sound, the higher its "pitch" as perceived by human ears. Frequency is measured in Hertz (Hz), or cycles per second. Roughly speaking, humans are able to hear sounds in the frequency range between 20Hz and 20,000Hz (20kHz).
GAIN
1) The process of amplifying a signal.
2) A way to express relative signal levels for audio. For instance, by adding 6 decibels of level to a signal, we double the perceived loudness of the signal. Also refer to decibel and headroom.
HEADROOM
Describes how much gain is left before a signal induces clipping or distortion. When recording with Peak, the record meters indicate how much headroom is left before clipping. When playing back audio in Peak, the meter strip at the bottom of the screen will indicate this as well. Most professional audio engineers leave between 3dB and 12dB of headroom while recording, to minimize the possibility of clipping. If you leave too much headroom, however, your signal may be recorded at too low a level, and you may end up with excessive noise or hiss. Also refer to clipping, decibel,and gain.
HZ (HERTZ)
This is the unit of measurement for frequency, and refers to the number how many "cycles per second" a sound wave generates. In the world of sound, the higher the number of Hertz, the higher the frequencyof a sound and hence the higher its "pitch" as perceived by human ears. A thousand Hertz can be expressed as 1kHz (one kilohertz), so that 20,000 Hertz may also be referred to as 20kHz.
LOOP
Loops are used to sustain or repeat a section of audio. They can be used for material that you intend to transfer to a sampler, or simply for playback within Peak itself.
PLUG-INS
Plug-Ins are optional software enhancements for Peak that are available from BIAS and other developers that support either the Adobe Premiere Audio Plug-In Standard, the Digidesign AudioSuite and TDM standards, and the Steinberg VST standard. By installing plug-ins in Peak's Plug-Ins folder, you can enhance Peak's audio editing and processing capabilities with tools such as filtering, reverberation, chorusing and flanging, noise reduction, spatialization, and more.
QUICKTIME
This is an audio format developed by Apple Computer for QuickTime-based multimedia. It is supported by all Macintosh software applications that support QuickTime. The QuickTime format is best if you plan to use an audio document in multimedia applications that support QuickTime, such as Adobe Premiere or Macromedia Director.
SAMPLE
(verb) Sampling refers to the act of recording audio material digitally by a sampling instrument or other digital recording device. See sampler and sample rate.
SAMPLE
(noun) A sample refers to audio material which has recorded digitally or "sampled" by a sampling instrument or other digital recording device. Sample also refers to a single wave-cycle" snapshot" of sound. See also sampler and sample rate.
SAMPLER
A sampler is an electronic instrument capable of digitally recording or "sampling" a sound and playing it back from a keyboard or other controller. Samplers are used extensively in all areas of audio production, ranging from recording and performance, to film production and sound design. See sample rate.
SAMPLE RATE
Sample rate describes how frequently an analog audio signal is been "sampled" or analyzed as it is recorded and converted to a digital medium. Sample rate directly affects audio fidelity in terms of upper frequency response: the higher the sample rate, the higher the available frequency response. A fundamental principle of sampling states that to accurately capture a sound, the sample rate must be at least twice the highest frequency in the sound. The standard sample rate for Compact Discs is 44.1 kHz. The following are common sample rates which are supported by many Macintosh computers and Peak software.
96.000KHz
This is the standard sample rate for Digital Video Disc (DVD) audio, and is often used by sound editors working in audio post-production for DVD. This rate results in an upper frequency response of 48kHz - well above the range of human hearing.
48.000KHz
This is one of two standard sample rates for digital audio tape (DAT) recorders, and is often used by sound editors working in audio post-production for video or film. This rate results in an upper frequency response of 24kHz- well above the range of human hearing.
44.100kHz
This is the standard sample rate for Compact Discs, digital audio tape (DAT) recorders, and high-fidelity audio applications on Macintosh and PC-compatible computers with 16-bit playback capability. It is colloquially called "forty-four one" (as in 44.1kHz). Most sound engineers working in music production - or anything that may be distributed on a CD - work at this rate. This rate results in an upper frequency response of 22,050Hz - above most people 's hearing range.
22.050kHz & 11.025kHz
These sample rates are sometimes used for lower-fidelity audio playback on Macintosh and PC-compatible computers. Many games, web-sites and other multimedia productions utilize 22.050kHz (or lower)8-bit audio, since it uses half the disc space of CD-quality audio. The 22.050kHz sample rate results in an upper frequency response of 12.025kHz; this may sound "muffled," since most people can hear considerably higher frequencies than 12.025kHz. Also refer to bit resolution, frequency, and Hertz.


FORMATOS

AIFF
 This is Apple 's Audio Interchange File Format.It is also Peak 's default file format and is supported by many Macintosh software applications.
Sound Designer II
 This is Digidesign 's audio file format for its digital audio products. Use this format if you wish to use an audio document in a Digidesign audio application.
.au
 This file format is commonly used on the World Wide Web and in Java audio applets. It is supported by many platforms and programs.
WAVE
 This is Microsoft 's Windows Audio File Format.It is supported by many Window 's software applications and some Macintosh applications. The WAVE format is best if you plan to use an audio document in an application that supports or requires WAVE format files.
QuickTime
This is Apple 's audio file format fo QuickTime-based multimedia. It is supported by all Macintosh software applications that support QuickTime.The QuickTime format is best if you plan to use an audio document in multimedia applications that support QuickTime, such as Adobe Premiere or Macromedia Director ™.
Raw
This is the header-less raw file format that may be useful for some game platforms.
RealAudio
 This is the file format for RealNet-works ™ RealAudio 5.0, 3.0 and 2.5 Encoders, used for preparing audio for streaming over the internet.
System 7 Sounds
 This the Apple audio file format used for Macintosh Operating System Sounds.
JAM image files
 This is the JAM audio image file format. JAM audio image files may be created in Peak and used in Adaptec JAM for burning audio CDs.
Sonic AIFF
 The file format used by Sonic Solutions audio workstations.
.paf
 This is the file format used by Ensoniq's Paris audio system. Note this file format favors mono and dual mono files.
Shockwave
 This is the file format used for Macromedia's Shockwave, for preparing audio for streaming over the internet.
MPEG-3 (MP3)
 This saves your document in MPEG-3 format.
MP4, etc.


HD STORAGE/ ARMAZENAMENTO

[O tamanho do ficheiro sonoro é directamente afectado pela 'sample rate' e pela 'bit resolution' da gravação digital: maior fidelidade/maior ficheiro.]

16-bit/44.1Khz/mono=5MB/min, stereo=10MB/min. 24-bit/44.1Hz/st=15MB.min.