38 terms

BCCA Chapter 8A Digital Sound

STUDY
PLAY
digital audio
music, speech, and other sounds represented in binary format for use in digital devices
music or voice that has been digitized into files using sampling techniques; sometimes referred to as waveform audio.
How is audio digitized?
1. a sound wave is sliced into vertical segments called samples
2. each sample is numbered
3. the height of each same is converted into a binary number
4. the sample number and binary number are stored
sampling rate
the number of times per second a sound is measured during the recording process
expressed in hertz (Hz)
higher sampling rates increase the quality of the sound recording, but require more storage space than lower sampling rates
from the Learning Objectives:
Why are some digital audio files so huge?
1. higher sampling rates increase the quality of the sound recording, but require more storage space
2. uncompressed
audio compression
techniques used to reduce the size of files that contain audio data
removes bits that represent extraneous noise and sounds that are beyond the frequencies of normal hearing
compressed audio files
require less storage space than uncompressed files and can be transmitted faster over a network
sound card
responsible for transforming the bits stored in an audio file into music, sound effects, and narrations
a circuit board that gives the computer the ability to accept audio input from a microphone, play sound files, and produce audio output through speakers or headphones
integrated audio
sound card circuitry that is build into the circuitry of a digital device, wherease a sound card is usually plugged into an expansion slot
digital signal processor
circuitry that is used to process, record, and play back audio files
three important tasks:
1. transforms digital bits into analog waves when you play a digital audio file
2. transforms analog waves into digital bits when you make a sound recording
3. handles compression and decompression, if necessary
From the Learning Objectives:
How do computers and portable media players such as iPods store digital music?
digital audio is stored in a variety or file formats
AAC
MP3
Ogg Vorbis
WAV
WMA
how do sound cards use a digital signal processor to convert bits into analog signals?
1. microprocessor sends compressed digital data to the sound card
2. sound card's digital signal processor decompresses data and converts it to analog signals
3. sound card sends analog signals to speakers
hardware needed for digital audio?
headphones, OR
speakers (built-in or plug in), and
microphone (built-in or plug in)
AAC
(Advanced Audio Coding)
audio file extension: .aac, .m4p, or .mp4
a file format (MPEG-4) that provides highly compressed audio files with very little loss of sound quality and is promoted by Apple on its iTunes Web site
MP3
(also called MPEG-1 Layer 3)
audio file extension: .mp3
a file format that provides highly compressed audio files with very little loss of sound quality
Ogg Vorbis
audio file extension: .ogg
an open source audio file format
WAV
audio file extension: .wav
an audio file format that was Windows' original sound format
WMA
(Windows Media Audio)
audio file extension: . wma
a file format that is promoted by Microsoft and provides highly compressed audio files with very little loss of sound quality
audio or media player
software needed to play a digital audio file
usually included in computer's operating system, or packaged with your sound card, or installed on a handheld device
usually supports several audio file formats
Web-based audio
digital audio files can be embedded into a Web page using HTML5 <audio> tag
often delivered in a streaming format to avoid lengthy delays while the entire audio file is downloading
streaming audio
an audio file format that allows the audio clip to begin before the file is entirely downloaded
audio converter software
changes audio files from one format to another
digital audio extraction
"ripping"
the process of copying files from an audio CD and converting them into a format that can be stored and accessed from a computer storage device, such as a hard disk
CDs use digital format CDDA
ripping converts and compresses
synthesized sound
artificially created (synthesized)
classified as MIDI
from the Learning Objectives:
What is the difference between digital audio and MIDI?
one is sound recorded
the other is sound synthesized
MIDI
(Musical Instrument Digital Interface)
a standardized way in which sound and music are encoded and transmitted between digital devices that play music
contain instructions for creating the pitch, volume, and duration of notes that sound like various musical instruments
stored with file extensions: .mid, .cmf., rol
MIDI sequence
digitally encoded MIDI music stored on a digital device, such as a computer of MIDI instrument
wavetable
(sometimes called a patch set)
set of pre-recorded instrument sounds in MIDI format
contained on a MIDI-capable sound card
sound card receives a MIDI instruction for piano middle C, accesses the piano's middle C patch, routes it to the speaker to play
MIDI advantages and disadvantages
more compact than digital audio files
does not produce high-quality vocals
does not have the full resonance (tone) of real sound
good for adding background music to multimedia projects
speech synthesis
process by which machines produce sound that resembles spoken words
speech recognition
the ability of a machine to understand spoken words
phoneme
basic sound unit
synthesizers string together these to form words
text-to-speech software
software that generates speech based on written text that is played back through a computer's sound card
how does speech recognition work?
system collects words spoken into a microphone connected to sound card
sound card's digital processor transforms analog sound into digital data
speech recognition software analyzes the sound of your voice and converts to phonemes
software compares phonemes to dictionary to determine language (English, French, Spanish)
software displays word on screen or use it to carry out a command
from the end of section A:
sampling
__________ rate refers to the number of times per second that a sound is measured during the recording process.
from the end of section A:
integrated
When sound card circuitry is incorporated into a computer system board, it is often referred to as __________ audio.
from the end of section A:
extraction
The process of ripping tracks from an audio CD to a digital format such as MP3 is call digital audio __________.
from the end of section A:
wavetable
MIDI sound is generated from a (n) __________ (or patch set), which is a set of prerecorded musical instrument sounds.
from the end of section A:
recognition
When a telephone-based airline voice response system asks you to say your flight number, it processes you response using speech __________ software.