Idle-Channel Noise

Idle-channel noise is noise present in a communications channel when no signals are applied.

The NI Sound and Vibration Measurement Suite measures the total power, the median noise density level, the maximum spur, and the signal-to-noise ratio (SNR) within the specified frequency range on waveform data or the complex spectrum returned by the other audio measurements.

For practical purposes, the returned idle-channel noise is a power-in-band measurement that returns the aggregate noise energy in the specified frequency range. The Sound and Vibration Measurement Suite computes the SNR as the full-scale level divided by the idle-channel noise.

The median noise level is normalized by the bin width, df, and is one measurement of the noise floor, or noise density level. You might find noise floor knowledge useful in advanced measurements.

Unlike gain, phase, and crosstalk measurements, idle-channel noise is a broadband measurement in which the amplitude of the fundamental frequency is expected to be zero.
Note When measuring idle-channel noise, make sure that the input channel of the device under test is floating, terminated, or excited with a zero amplitude signal.