GLOSSARY OF NOISE TERMINOLOGY
Term
Definition
Proposed to
be defined in
District Plan?
NO
A-weighting
The process by which noise levels are corrected to account for
the non-linear frequency response of the human ear.
C-weighting
The process by which noise levels are corrected to account for
non-linear frequency response of the human ear at high noise
levels (typically greater than 100 decibels).
NO
Z-weighting
A Z-weighted level is an “unweighted level”, i.e. the sound level
expressed has had no corrections applied to account for how the
human ear may respond to it.
NO
dB
Decibel - The unit of sound level.
NO
This measure expresses the “sound pressure” (in Pascals) in a
logarithmic form. A decibel is essentially a ratio of the measured
pressure level compared with the quietest sound a person can
hear.
dBA
The unit of sound level which has its frequency characteristics
modified by a filter (A-weighted) so as to more closely
approximate the frequency bias of the human ear.
NO
HZ
Hertz is the unit of frequency. One hertz is one cycle per second.
One thousand hertz is a kilohertz (kHz).
NO
LAE (Sound
Exposure Level)
means the sound level of one second duration which has the
same amount of energy as the actual noise event measured. This
is usually used to measure the sound energy of a particular event,
such as a train pass-by or an aircraft flyover.
YES
LAeq (Time
Averaged Sound
Pressure Level):
means the time-averaged, A-weighted sound level measured in
decibels (dB).
YES
LAFmax (Maximum
Sound Level):
means the maximum, A-frequency-weighted, fast-time-weighted
sound level, in decibels (dB), in a given measurement period.
YES
LCpeak (peak Cweighted
pressure level)
means the peak instantaneous C-weighted pressure level
recorded during the measurement period. The “peak” level is not
RMS averaged within the measurement circuitry of the sound
level meter and therefore can appear much higher than other
levels of instantaneous noise levels such as LAFmax.
YES
Ldn (Day/Night
Level)
means the day-night sound level which is calculated from the 24
hour LAeq with a 10 dB penalty applied to the night-time (22000700 hours) LAeq to account for potentially increased annoyance
during this time.
YES
LZpeak
The peak instantaneous pressure level recorded during the
measurement period without any weighting applied. LZpeak and
LCpeak levels are often similar.
NO
PPV (Peak
Particle Velocity)
means the measure of the vibration aptitude, zero to maximum.
This parameter can be used for assessing building structural
damage and also has application to human annoyance.
YES
RMS (Root Mean
Square) Velocity
For most applications where there is continuous vibration,
vibration is measured in terms of root mean square RMS velocity
(mm/sec), measured in any direction. Used for vibration
annoyance.
YES
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