New Zealand’s FM broadcast licenses don’t stipulate constraints on the maximum permitted modulation, only the maximum occupied bandwidth. This gives Kiwi broadcasters slightly more scope for their on-air processing but people should be wary of how consumer receivers handle over-modulation.
Orban’s Greg Ogonowski’s paper “Achieving Maximum Modulation and Effective Loudness in FM Stereo Broadcasting” is a great read for stations looking to understand more about the black art of broadcast processing and make the most of modern digital processors.
Broadcast audio processing is both an engineering and artistic endeavor. The engineering goal is to make most efficient use of the signal-to-noise ratio and audio bandwidth available from the transmission channel while preventing its overmodulation. The artistic goal is set by the audio processing user. It may be to avoid audibly modifying the original program material at all. Or it may be to create a distinct sonic signature for the broadcast by radically changing the sound of the original. Most broadcasters operate somewhere in between these two extremes.Greg Ogonowski