Alert readers may recall that for the past year I’ve been devoting most of this column to the CALM Act and the related issue of audio levels and loudness in broadcast television audio.

Dave Moulton takes another look at TV audio levels in advance of the CALM Act next month.

I don’t know how many TV Technology readers know of Neil Muncy. However, it is highly improbable that any of us haven’t heard his work.

You may recall that we’ve been grappling with the measurement of audio loudness and the implications of the ITU’s B.S. 1770-1 standard for the measurement of loudness, in support of the CALM Act.

“I’m a TV engineer from the old school, so of course I never read articles about audio. The CALM Act changes that, of course.”

The protocol is for modifying the television audio signal to measure its magnitude in a way that more closely agrees with humans' subjective sense of loudness

My measurements sought to examine the question of variance of audio levels between channels and how this variance has changed (or not) over time.

The first thing to keep in mind is that we are talking about a pair of signals here, not a single mono signal.

You may recall I've been ranting about variance in loudness levels on broadcast television for numerous years.

A key ingredient of almost any successful stereo production

As we've discussed, low frequencies don't do well coming out of small loudspeakers into smallish rooms.

Stable, consistent and predictable bass is one of the hardest things to obtain in a monitoring situation.

This is not easy to do, and impossible to do perfectly.

This will actually take a couple of columns. I'll start with the idea of standing waves.

There are issues of dynamic range, maximum and minimum levels, subjective loudness qualities, spectrum and much more.

Their performance and effectiveness can be highly variable for a range of not-so-obvious reasons.

It seems appropriate to me that we go a little further with the discussion, simply to clarify what seems to be meant and desired in practice by A/85 and its authors.

We would like all equipment to play back at the same calibrated level, including in our viewers' homes. To achieve that, we use a protocol called dialnorm.

24 dB below Full Scale (zero LKFS) is the new mandated nominal, or "target," level for audio broadcast.

Not all crumminess sounds the same.

You need to get a handle on the actual measured levels at which you are working.

You need a room—pretty much all to yourself and big enough so others can join you on occasion.

You need good speakers, placed well in a good room.