Averaging Over Time (Temporal Averaging)

Temporal averaging just means averaging a measurement over some period of time. Typically this is done at a single measurement point or microphone position, although moving-microphone measurements utilizing temporal averaging are sometimes used for specialized applications. In acoustical measurements, a significant amount of noise from various sources gets mixed in with the signal we are trying to measure. The noise components are random, meaning they are different in each individual “frame” of incoming measurement data, and fluctuate quite a bit from one frame to the next. This tends to make the charts jump around a lot and look noisy and hard to read.

The averaging selections for Spectrum (Left) and Transfer Function (Right) measurements. Spectrum includes None, as well as Fast and Slow (corresponding to SPL Meter integration periods of 125ms and 1000ms, respectively).

See: What do the Averaging Values 1-10 Mean in Smaart?

Averaging over time increases the signal-to-noise ratio of a measurement through a process known as regression to the mean. The noisy parts of the incoming data, being more random than the signal component, tend to cancel each other out when aggregated over time. The signal components, being either stationary features (in the case of steady state system measurements where the signal being measured is not changing rapidly) or at least less random than the noisy parts (when analyzing dynamic signals), tend to average out to themselves, becoming smoother and easier to see.

The trade-off is responsiveness. When analyzing the spectral content of dynamic signals, too much averaging can mask fluctuations that are part of the actual signal and may be things you need to see. In system response measurements, excessive averaging makes the measurement slow to respond to changes in system settings such as equalization and delay adjustments. The trick is to try and use just enough.

For electronic measurements, you can typically get away with very little averaging. In acoustical measurements, the amount of averaging needed varies with background noise levels and user preference. One thing you can do to help speed up the system equalization and alignment process when measuring in a noisy environment is to press the [V] key after making a settings change. This flushes the averaging buffers and restarts the average, so that you don’t have to wait for the oldest data to fall out of the measurement before you can begin to see the result of your changes.

Temporal averaging for real-time measurements is set from the Averaging control on the Control Bar that runs down the right side of the main window. The available options are a mix of types as well as degree of averaging.

Next: What do the Averaging Values (1-10) Mean in Smaart?