TR41.3.5-15-04-007
8.1 Idle-Channel Noise
Idle-channel noise is the short-term, average, absolute noise power measured with 3400 Hz flat or
psophometric weighting in the absence of signal. In addition, it is also measured using a the 300 to 6400
Hz flat weighting function noise filter defined in Annex A.8 for wideband channels.
Compliance with the idle-channel noise requirements should be determined as described in Annex A.8.
8.1.1 3400 Hz Flat Noise
The 3400 Hz flat noise shall not exceed -51 –60 dBm when measured on an analog-to-analog
connection. For interface transmission levels other than 0 dB, the 3400 Hz flat noise requirement
remains at –60 dBm because the bulk of the noise is usually generated at the output of the digital-toanalog conversion and doesn’t scale with the loss setting. should be shifted by a value that corresponds
to the difference between the transmission level at that interface and 0 dB.
8.1.2 Psophometric Weighted Noise
The psophometric weighted absolute noise power at an interface shall not exceed the limits given in Table
15. For interface transmission levels other than 0 dB, the psophometric weighted noise requirement for an
analog-to-digital connection type should be shifted by a value that corresponds to the difference between
the transmission level at that interface and 0 dB. The psophometric weighted noise requirement for a
digital-to-analog connection type remains constant across all transmission levels. The psophometric
weighted noise requirement for an analog-to-analog connection type should be computed by doing a
power sum of the analog-to-digital requirement adjusted for the A/D and D/A gains and of the digital-toanalog requirement.
Table 15 – Voice Gateway Psophometric Weighted Noise Requirements at 0 TLP
Psophometric Weighted Noise in the
Absence of Signal (dBmp)
Connection Type
Limit
Analog-to-analog
-69
Analog-to-digital
-70
Digital-to-analog
-76
8.1.3 Wideband Flat Noise
The maximum unweighted flat noise in the using the 300 to 6400 Hz band filter shall not exceed -66 dBm
for wideband transmission channels for an analog-to-digital or a digital-to-analog connection type. For
interface transmission levels other than 0 dB, the wideband flat noise requirement for an analog-to-digital
connection type should be shifted by a value that corresponds to the difference between the transmission
level at that interface and 0 dB. The wideband noise requirement for a digital-to-analog connection type
remains constant across all transmission levels.
Note: The requirement for wideband flat noise is more stringent than for 3400 Hz flat noise, but power
line harmonics that might be included in the 3400 Hz measurement are attenuated by the filter roll off
below 300 Hz in the wideband measurement.
8.1.4 Single Frequency Interference (SFI)
Single frequencies and very narrow bands of noise can be perceived as tonal impairments depending on
their level relative to the overall noise level. This test measures the weighted noise level characteristics
in narrow 30 Hz bands over the range from 100 Hz to 4000 Hz for narrowband channels and over the
TR41.3.5-15-04-007
range from 100 Hz to 8000 Hz for wideband channels. For an analog-to-digital or a digital-to-analog
connection type all transmission directions, the peak narrow-band 30 Hz band noise products, including
single frequency interference, shall be less than -76 dBm. For interface transmission levels other than 0
dB, the SFI requirement of an analog-to-digital connection type should be shifted by a value that
corresponds to the difference between the transmission level at that interface and 0 dB. The SFI
requirement of a digital-to-analog connection type remains constant across all transmission levels.
Note: If the wideband flat noise measured for 8.1.3 does not exceed -76 dBm0, SFI testing is not
required.
A.8 Idle Channel Noise
A psophometer complying with ITU-T Recommendation O.41 should be used for making psophometric
weighted noise measurements. A filter with appropriate pass band characteristics in series with a
wideband voltmeter should be used for making the flat noise measurements. A second order low-pass
Butterworth filter with a 3400 Hz corner frequency should be used for the 3400 Hz flat noise
measurements.5 A third-order Butterworth band-pass filter with corner frequencies of 300 and 6400 Hz
should be used for the wideband flat noise measurements.6 Alternatively, the measurement may be
made by power summing the noise signal over the specified 30 Hz to 16 kHz frequency band using a
spectrum analyzer with a maximum resolution bandwidth of 100 30 Hz from 30 Hz to 3 kHz and 100 Hz
from 3 kHz to 16 kHz, and applying the appropriate weighting factors at each frequency.