- Lower case d when used as a prefix will
be the short form of deci.
- Pronounced decibel or just dB. Gives an
logarithmic relation between two powers. The scale follows the
db = 10 * log --
P1 is the reference or input power
P2 is the output power
0 dB means that the powers of P1 and
P2 is equal. 10 dB means that the power P2 is 10 times higher than
P1. 20 dB means that the power P2 is 100 times higher than P1 and in
the same way will -10 dB means that P2 is a tenth of the power of
P1. Decibels is really an dimensionless scale, but it allways means
the effective power ratio measured along a logarithmic scale.
- An dB scale where the reference power is fixed
at 1 mW. This scale is very common for use with signal strength of
various kinds, both electrical and optical. The scale follows the relation
dBm = 10 * log -----
P is the power of the signal
- An dB scale which gives the relative power
relation between a measured power strength and a suitable reference
signal's power strength. It is suitable to indicate difference as
opposed to an actual power strength. The scale follows the relation
dBr = 10 * log --
Pm = power measured at the output of the system
Pr = power of a suitable input (reference) signal to the system
- An dB scale for acoustical sound pressure being
referenced to 20 uPa (micro Pascal). It is usefull for acoustical
sound pressure measurements.
- An dB scale where the reference power is
replaced with an reference voltage (appoximatly 0.775 V) which will
give an effect of 1 mW over an 600 ohm resistance. This unit is used a
lot in teletransmission and audio since it is easier to measure the
voltage alone then measuring the true power.
- An dB scale similar to dBu
but differs in the sense that it will reference to exactly 1 V instead
of an derived voltage (as in the dBu case).
- Decay is a term used for envelopes.
It is the period when the envelope falls from its peak level (as
developed during the attack)
down to the sustain level. The decay
period is started when the attack has
reached its peak value.
- An d in
most shorter notations. It is part of the SIS standard but is not to
be preferred, never the less it is widely used and will probably not
go away in forseeable future.
- An Bel scale with the prefix
deci attached to it. The decibel scale has become
a popular scale within teletransmission, telecommunication, audio and
everywhere else where and relative power scale is of interest. It will
give the ratio of a power compared to a reference power or the ratio
between two powers converted into a logarithmic scale.
- Delay is a phenomene by which a signal occurs at some later time
than the causuallity would allow. An signal sent into some system
is said to be delayed by the amount of time it takes for the
signal to pass from the input of the system to the output of the
system. A relative delay can exist between two diffrent outputs of
the same or two diffrent systems given the same input signal. A
system that intentionally provide some (possibly variable) delay
to the applied signal is often called a delay or a delay
unit. Such a unit will delay the signal with ideally no distorsion
of the signal waveform.