HP 4934A - Impulse Noise Measurement Principles

Impulse Noise
Principles
Impulse noise includes noise spikes like the clicks and pops often heard on a
telephone line. The spikes are much higher in level than the background
noise and, generally, last less than one millisecond.
The impulse noise measurement counts the number of noise spikes against 3
threshold levels simultaneously. The low level threshold is selectable; the
medium and high thresholds are fixed at 4 dB and 8 dB above the low thresh¬
old.
The waveform (b) below illustrates a received holding tone (or test tone) that
includes interfering impulse noise spikes.
(a)
TRANSMITTED
HOLDING TONE
(b)
RECEIVED
HOLDING TONE
WITH IMPULSE
NOISE SPIKES
TIME
Making Measurements 2-17