Difference between"RMS average" and "vector average"

Horst · Dec 28, 2023

Hi

what is the exact Difference between"RMS average" and "vector average" ?

Thanks Alpi

John Mulcahy · Dec 28, 2023

From the All SPL graph help:

RMS average, which calculates an rms average of the SPL values of those traces which are selected when the button is pressed. This does the same as the Average The Responses button, the dB values are converted to linear magnitudes, those magnitudes are then squared, summed and divided by the number of measurements, the square root of the result is taken, then the value is converted back to dB. Phase is not taken into account, measurements are treated as incoherent. If only a single trace is selected the result has the magnitude data from the source measurement and no phase data. If the measurements were made at different positions (spatial averaging) it is usually best to first use the Align SPL... feature to remove overall level differences due to different source distances. When measurements with distortion data are averaged their distortion data is also averaged, providing the data cover the same frequency range at the same resolution.
dB average, which averages the dB SPL values of the currently selected traces. This produces results that are closer to what one might intuitively expect from looking at the traces, but gives equal weight to peaks and dips which masks the magnitude difference between them. For example, a +20 dB peak has a magnitude that is 100 times larger than a -20 dB dip. dB averaging them produces 0 dB, 10 times smaller than the peak and 10 times larger than the dip. dB averaging may be useful when averaging smoothed traces to derive an EQ target, with unsmoothed data the dips would have a disproportionate effect on the result. When measurements with distortion data are averaged their distortion data is also averaged, providing the data cover the same frequency range at the same resolution.
Vector average, which averages the currently selected traces taking into account both magnitude and phase. It can only be applied to measurements that have an impulse response and is most appropriate for multiple measurements taken from the same position, or measurements which have been time and level aligned before averaging them. When measurements with distortion data are averaged using Vector average their distortion data is also averaged, providing the measurements were made at the same sample rate and with the same sweep settings.
RMS + phase avg. and dB + phase avg., which produce an RMS or dB average of the magnitudes and use vector average for the phases. They can only be applied to measurements that have an impulse response. Both are appropriate for multiple measurements of a source. Measurements should be time and level aligned before averaging them, cross correlation alignment is recommended for the time alignment. These averaging methods do not exhibit the magnitude dips due to phase cancellations that can occur with vector averaging. The resulting impulse response may have significant acausal content as the relationship between magnitude and phase that would normally hold is broken. As a result the average requires larger left windows than usual. The effects of any calibration files of the individual measurements are merged into the resulting impulse response.

Horst · Jan 2, 2024

First- wish you and all here a happy new Year!
Thanks i will read it and hope i understand

lg

Difference between"RMS average" and "vector average"

Horst

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John Mulcahy

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Horst

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