Digital Music Midterm Exam Terms
MP3
Stands for MPEG-1, Audio Layer 3. It is a digital audio file format. It is currently the most popular format on the web because of its high sound quality and small file size.
Impedance
A measure of electrical resistance specified in ohms.
Decibel
A unit of measurement (named after Alexander Graham Bell) that describes the strength of a signal relative to a standard reference.
Peak
Maximum instantaneous level of a signal.
Hertz
A unit of measurement denoting frequency, originally measured as cycles per second.
Digital Audio
Refers to a way of synthesizing sound. In this format sound waves are broken down and assigned a numerical value, represented by groups of 1s and 0s. When these groups of numbers are read by a receiver or amplifier, they are converted back into sound. This kind of mathematical precision creates crisp, clean sounds.
VU
A visual meter designed to interpret signal levels in roughly the same way as the human ear, which responds more closely to the average levels of sounds rather than to the peak levels.
Fade Out
A feature of most audio editing software that allows the user to apply a gradual amplitude decrease over some segment of the sound.
Analog
The traditional means of recording and reproducing sound, using fluctuating electronic voltages to replicate audio waveforms. The origin of the term is that the electrical signal can be thought of as being analogous to the original signal.
Ripping
This is the process of taking audio data from your CD and making it into a sound file on your computer.
Frequency
The rate per second at which an oscillating body vibrates. Usually measured in Hertz(Hz).
Attenuate
To make lower in level.
Encoding
This is the name for the process in which larger sound files are compressed into smaller ones. When you convert a file from WAV format into an MP3 file, you are doing this.
Overload
A condition in which a system is given too high an input level. A common cause of distortion or product failure.
Amplifier
A device which increases signal level (loudness). They typically increase voltage, current or both.
AMP
Unit of electrical current.
Ohm
Unit of electrical resistance.
Compression
In audio, it means to reduce the dynamic range of a signal.
Wavelength
The distance the sound wave travels to complete one cycle. The distance between one peak or crest of a sine wave and the next corresponding peak or crest.
CDR
A record able compact disc format, allowing just one record cycle (it cannot be erased and reused).
Byte
A piece of digital data comprising (normally) eight bits.
MIC level
The low level signal generated by a microphone. This must be amplified many times to increase it to line level.
Pitch
A continuous frequency over time.
Stereo
From the Greek meaning solid. The purpose is not to give you separate right and left channels but to provide the illusion of a three-dimensional, holographic image between the speakers.
Bandwidth
A means of specifying the range of frequencies passed by an electronic circuit such as an amplifier, mixer or filter. The frequency range is usually measured at the points where the level drops by 3dB relative to the maximum. It is the total frequency range of the system, usually specified as something like: 20-20,000Hz plus or minus 3 db.
Line Level
The high level input or output analog signal generated by direct connection.
Distortion
Anything that alters the musical signal (a process often found desirable by guitar players).
Dynamic Range
The difference between the loudest (maximum output level) and quietest (residual noise floor) sounds produced in an audio system without distortion.
Sample rate
A digital representation of an analog signal created by checking, or recording, the analog voltage a fixed number of times per second. CD quality is 44.1kHz; per second.
Cycle
One complete vibration of a sound source or its electrical equivalent. One of these is would be expressed as 1 Hertz.
Codec
Acronym for Compressor-Decompressor; the complicated mathematical algorithms used to create and read compressed digital audio files.
Decoding
This is the process whereby the information in a compressed digital audio file is read so that it can be played and heard.
Balance
The relative levels of the left and right channels of a stereo recording, or the relative levels of the various instruments and voices within a mix.
Normalization
An automatic process available in most audio software whereby the gain of all program material is adjusted so the peak level will just arrive at 0 doffs.
XLR
Type of connector commonly used to carry balanced audio signals, including the feeds from microphones.
Condenser
A high quality type of microphone that needs a power source.
Aliasing
When an analog signal is sampled for conversion into a digital data stream, the sampling frequency must be at least twice that of the highest frequency component of the input signal. If this rule is disobeyed, the sampling process becomes ambiguous as there are insufficient points to define each cycle of the waveform, resulting in enharmonic (false) frequencies being added to the audible signal.
Burning
This term usually refers to the act of writing information (data, music, etc.) on to a compact disc.
Jitter
Timing variations, a tendency towards lack of synchronization caused by electrical changes. Technically the unexpected (and unwanted) phase shift of digital pulses over a transmission medium. A discrepancy between when a digital edge transition is supposed to occur and when it actually does occur.
Buffering
The method for temporarily storing or delaying data samples before processing or conversion.
CD
Abbreviation for a compact disc.
Nyquist
The last name of the men who developed the process of sampling audio with a digital system. The theory they developed states that the sampling frequency of a digital audio system must be at least twice that of the highest audio frequency, otherwise aliasing will occur.
Balanced
Wiring system which uses three wires two out-of-phase conductors and a common screen to reduce the effect of interference.
DAC
Circuitry that converts a digital (binary) signal into an equivalent analog waveform. In an audio system, this is done so the signal from digital storage media, such as MiniDisc, CD, or Digital Audio Tape, can be handled by analog system components, such as the receiver and speakers.
Amplitude
Another word for level. Can refer to sound levels or electrical signal levels. It is the height of a waveform.
KHz
Abbreviation for 1000 hertz
WAV
A digital audio file format. It is not a compressed format, so these files are usually very large. It is often used as an intermediate format when recording from a CD.
Dynamic
A type of microphone that works on the electric generator principle, where a diaphragm moves a coil of wire within a magnetic field.
Dynamics
The relative loudness or softness of a piece of music.
ADC
Circuit for converting analog waveforms into a series of equally spaced numerical values represented by binary numbers. The analog signal is sampled every few milliseconds and its level is quantized into a digital word