NAB (National Association
of Broadcasters) A professional trade organization for people
working in the radio and television industry.
NAMM (National Association
of Music Merchants) A professional trade organization for
people working in the music (MI) business -- primarily in retailing
and manufacturing of music products.
nano- A prefix for one billionth (10E-9), abbreviated n.
NARAS (National Academy of Recording
Arts & Science) See The
narrow-band filter Term popularized by equalizer pioneer
C.P. Boner to describe his patented (tapped toroidal inductor) passive
notch filters. Boner's filters were very high Q (around 200) and
extremely narrow (5 Hz at the -3 dB points). Boner used 100-150
of these sections in series to reduce feedback modes. Today's usage
extends this terminology to include all filters narrower than 1/3-octave.
This includes parametrics,
notch filter sets, and certain cut-only
variable equalizer designs. See notch
Network Generally used to mean a multi-computer system
configured to share information and resources. Characterized by full two-way (duplex)
communications between all devices on the network. Nodes on the
network may include computers, printers, scanners and other devices.
The types of devices found on the network is rapidly expanding
including audio and video control and conferencing systems.
nibble A group of four bits or half a byte
Noise meaningless sound produced as a
by-product of unintentional or unrelated activities. In electrical
circuits, the random noise "hiss" produced by all components in the
circuit. Unless dealt with properly this background noise can
build up or become amplified to the point that it interferes with
the desired signal or makes the circuit unusable. See
Signal to Noise Ratio.
noise floor Normally the lowest threshold of useful signal
level (although sometimes audible signals below the noise floor
may be recovered).
noise gate An expander
with a fixed "infinite" downward expansion ratio. Used
extensively for controlling unwanted noise, such as preventing "open"
microphones and "hot" instrument pick-ups from introducing
extraneous sounds into the system. When the incoming audio signal
drops below the user set-point (the threshold point) the
expander prevents any further output by reducing the gain to "zero."
The actual gain reduction is typically on the order of -80 dB, thus
once audio falls below the threshold, effectively the output level
becomes the residual noise of the gate. Common terminology refers
to the gate "opening" and "closing." Another
popular application uses noise gates to enhance musical instrument
sounds, especially percussion instruments. Judicious setting of
a noise gate's attack (turn-on) and release (turn-off)
times adds "punch," or "tightens" the percussive
sound, making it more pronounced.
noise shaping A technique used in oversampling
low-bit converters and other quantizers to shift (shape)
the frequency range of quantizing
error (noise and distortion). The output of a quantizer is fed
back through a filter, and summed with its input signal. Dither
is sometimes used in the process. Oversampling A/D converters shift
much of it out of the audio range completely. In this case, the
in-band noise is decreased, which allows low-bit converters (such
as delta-sigma) to
equal or out-perform high-bit converters (those greater than 16
bits). When oversampling is not involved, the noise still appears
to decrease by 12 dB or more because it is redistributed into less
audible frequency areas.
notch filter A special type of
cut-only equalizer used to attenuate
(only, no boosting provisions exist) a narrow band of frequencies.
Three controls: frequency, bandwidth and depth,
determine the notch. Simplified units provide only one or two controls,
with bandwidth and/or depth fixed internally. Used most often in
acoustic feedback control to eliminate a small band of frequencies
where the system wants to howl (feedback). See narrow-band filter.
nonvolatile Refers to a memory device which does not lose
its data when power is removed from the system.
NSSP (National Standards
Systems Network) A Web-based service launched by ANSI,
along with government and industry partners. A full search &
sales service provides for locating and buying virtually any standard.
Planners say more than 100,000 global standards will be available
on the data base by the end of 1997. Over 25 standards groups are
providing technical specs for the new database, including ISO.
The EIA endorsed the project.
NTSC (National Television systems Committee) The analog
video standard used for television broadcast and composite video
connections in the United States. The NTSC format
standard is administered by the Federal
Communications Committee (FCC). NTSC signals encode video
as 525 horizontal lines of pixels. The lines are scanned in odd and even sets at 1
field (1/2 frame)
every 60th of a second (to work with the US power standard of
60cps), resulting in am effective video frame rate of 30fps. NTSC is
one of three main television standards throughout the world. See PAL
null modem cable Special
wiring of an RS-232
cable such that a computer can talk to another computer without
a modem (thus "null" modem). As a minimum a null modem
cable reverses pins 2 and 3 on a standard RS-232 cable.
Nyquist frequency The highest
frequency that may be accurately sampled. The Nyquist frequency
is one-half the sampling
frequency. For example, the theoretical Nyquist frequency of
a CD system is 22.05 kHz (44.1kHz/2).