Here’s Part 3—We’ll probably have 2 more of these before we’re
Dolby A, B, C,
and DBX—Dolby Laboratories came up with a noise reduction system in
1966 known as Dolby A which offered a 10db noise reduction over 4 bands by
boosting the signal above 1Khz and then the opposite takes place upon
playback. Dolby B was developed to reduce noise from cassette hiss and has a
10db noise reduction on frequencies over 1khz. Tapes encoded with Dolby B
will sound acceptable on players not equipped with Dolby B decoders. Dolby C
has 20db reduction on high frequency noise but sounds much worse than Dolby B
recordings on equipment that doesn’t have Dolby C decoding. Both Dolby B and
C use a process by which the amount of boost/cut is determined by the dynamic
level of the signal. A low level signal will have the most boost whereas a
hotter signal will have little or no boost/cut applied to it. DBX is a rival
noise reduction scheme developed by the company of the same name. The process
involves companding or compressing the signal by a factor of 2 when recorded
and then expanding the signal upon playback.
Doubling—A track can be “doubled” in one
of three ways—recording the performance again, electronic doubling using
delay or chorus or copying the track and time shifting it slightly. It is
very effective in helping a track sit in a mix better and was originally used
to increase the volume of a part.
Ducking—involves lowering background music
as in a voice-over so that the spoken part doesn’t have to compete with the
musical bed. Usually accomplished using a sidechain compressor—see my article
Dynamic Microphone– A microphone that
doesn’t require external power. Shure’s SM-57 and Sm-58 are probably the most
popular examples of a dynamic microphone
Dynamics—The dynamic range of a track is
determined by the difference between the loudest and softest parts. If the
loudest part is –3db and the softest part is –60db the dynamic range is
–57db. Dynamics also refers to the apparent softness and loudness of a song
where the verse may have clean electric guitar and softer elements and the
chorus is accompanied by distorted electric guitar, louder background and
lead vocals and more energy overall.
Effects—Chorus, compression, limiting,
gating, reverb, etc. In other words, it is electronic (and otherwise)
manipulation of the original track in order to achieve a desired feel and
EQ—Equalization, an effect where
particular bands of the sonic spectrum are boosted or cut. Used in mixing to
help tracks “sit” in the mix.
Fade Out—used in mixing and mastering to
slowly decrease the volume of a track until silence is achieved. Often used
to fade one track into another on a CD
Feedback—When the original signal is fed
back into the circuit, a loop is created that regenerates until the circuit
is overloaded.. The result can be undesirable as in squealing microphonic
feedback or can be desirable as when a electric guitarist uses feedback in a
Fletcher-Munson Curve—The human ear is
less sensitive to lower frequency noise and more sensitive to higher
frequency noise with the highest sensitivity between 1 and 5 Khz. The
Fletcher-Munson curve describes this by graphing the sound pressure level
required to achieve the same apparent volume at different frequencies from
Gobo/Baffle– Gobo (Go Betweens) and
Baffles are used in recording to sonically separate performers so that each
track only contains the information from one performer.
Harmonics—additional tones produced by an
instrument or vocals that determine their timbre. As an example, when one
plucks the open “A” string on a guitar, the loudest tone generated is 440hz.
The harmonics of the note are all multiples of 440 hz in varying levels.
Hertz- used to describe electrical and
sound vibrations by the the number of cycles per second. A 2000 hz (2Khz)
signal has 2000 cycles per second
Isolation Room— Also known as a vocal or
sound booth. Used to isolate the vocalist from outside noise or to isolate a
drummer from the outside performers.
Leslie Effect– comes from the rotating
Leslie speaker used with Hammond B3 organs and electric guitarists. As the
speaker rotates, the Doppler effect comes into play such that as the speaker
rotates toward the listener, the apparent tone of the instrument seems to
rise slightly and the as it rotates away it decreases slightly. It is also
accompanied by a slight raising and lowering of the apparent volume since at
different points in time, the speaker is pointed some degree either toward or
away from the listener.
Mastering—Using compression, limiting,
equalization and reverb so that all the tracks on a CD have a similar
loudness and tone
Mic Pad—Some microphones have a 15 or 20db
level reduction built into them so that they can be used with louder sources
such as guitar amplifiers without distortion. Some mixers also have this
feature but it is used to tame line level sources such as keyboards.
MIDI Channel—Assignation used to separate
midi instruments from one another in a midi file. For instance, percussion
(including drums) is usually relegated to channel 10. You might want to have
the piano part on channel 1, the bass part on channel 2 and so on so that
each instrument can be controlled separately
MIDI Pressure (Aftertouch) -A feature of
more modern keyboards where as the key is lifted an effect is applied to the
sound generated such as vibrato, or a filter sweep.
MIDI Track—Similar to an audio track where
all the information for a particular midi performance is stored
MIDI Velocity—The midi equivalent of
loudness—it records how fast the key is depressed.
Continued next month