Euphonix System 5 Application Note

System 5 Metering: Peak vs. Average
Product: System 5 Software
Audience: Broadcast, Post-Film, Music
Subassembly: eMix software
Customers have been asking us why a sine wave registers a different level in the Peak and
Average metering modes on the Euphonix System 5 console. Some customers are also
confused why a Dorrough Loudness Meter registers the same value for peak and average
measurement of a sine wave.

Terminology

Figure 1 shows a sine wave through a complete 360° cycle. The graph depicts voltage (y-axis)
changing over time (x-axis). To determine the peak and average levels of this sine wave,
we must rectify it, which converts the AC voltage to DC (i.e., flips the negative voltage to
positive). The peak level is determined by the maximum amplitude above the zero line,
which requires no calculation, just remembering the maximum voltage.
The root mean square (RMS) average, which describes the energy within the sine wave, is
calculated using instantaneous voltages measured over a complete cycle. A sine wave has
an RMS value of 0.707 times its peak value. On a logarithmic dB scale, the difference be-
tween a sine wave's peak and RMS average level is 3 dB.
Euphonix bases its metering on the Audio Precision measurement system, which adheres
to the RMS average technique. What you see on a Euphonix meter is the mathematical
truth!
1
0
1
Application Note 1
1
0
Sine Wave
Figure 1 Sine Wave
Software Version:
Document Revision:
Date:
Rectified Sine Wave
All
1.1
January, 2002
Peak Level = 1