Focus: The Immersive Sound Analyzer

Mike Kahsnitz Senior Director of Product Management, RTW

September 21, 2019

With new immersive sound formats such as Dolby Atmos, the audio world is having an increased focus on audio formats with a large number of audio channels.

For us as a metering focused company, the challenge is to measure and display all of these channels in a way that is usable in the many immersive audio applications, and the Immersive Sound Analyzer is our take on an instrument that can get you relevant technical and subjective parameters of formats such as 5.1.4 or even 7.1.4 in a fast and intuitive way.

As we wanted to stay as close as we can to our unique Surround Sound Analyzer, which a lot of audio engineers are already familiar with, some of the features are the same, and to understand more about the details of the Immersive Sound Analyzer, you might want to read our blog post on the SSA .

The examples in this article will be based on a standard 5.1.4 Dolby Atmos setup.

The Components of the ISAFirst, let us have a look at each individual component of the Immersive Sound Analyzer. There are components for each of the main and upper layers, and there is also a component that shows the relationship between the layers.

5.1 Main Bed

The Total Volume Indicator displays the total volume and balance of the audio material in a single view. The lengths of the bar graphs that go out from the center show the sound pressure level or loudness.

The blue, outlined area shows the 5.1 main bed signal image including its center channel signal.

The white crosshairs is the so-called Dominance Indicator (DMI) that shows the position of the subjectively perceived acoustic focal point.

5.1 Main Bed View

4.0 Upper Bed

The orange area shows the volume and balance of the upper bed.

Our power users will immediately recognize that the Dominance Indicator (DMI) crosshairs is tilted 45 degrees and we have done this to maintain a clear distinction between the main and upper bed DMIs

4.0 Upper Bed View

The Relation Between the Main and the Upper Bed

The relationship between the main and upper beds is indicated by the size of a white dot, and as you can see here, the white dot sits between the main and upper bed dominance indicators.

The dot is called the Immersive Dominance Indicator (IDI) and the position and size of it indicates the loudness relation between the main and the upper bed.

A very small dot indicates that there is audio only in the main bed, and a large dot indicates there is audio only in the upper bed.

The relationship between the main and upper bed is indicated by the size of a white dot

Main- and Upper Bed Combined

Here you see the combination of the main bed and upper bed, including the IDI dot.

Once familiar with the display, you get a fast and intuitive overview of a 5.1.4 signal.

Main and Upper Bed Combined

Full ISA View

The Immersive Sound Analyzer displays Total Volume Indicators for both beds simultaneously, and the position and height of the dominant signal is shown by a white dot.

The phase correlation bars display the phase relation between the different sources of the selected bed.

Like the phase correlation bars, the Phantom Source Indicators (PSI) show relations between each of the channels in a surround mix of the selected bed.

The perceived position and its height, the ambient signal (TVI) of the two beds and the spreading and phase correlation of a selectable bed can be displayed simultaneously in one easy-to-read view.

Full ISA View

Practical Use

Fast and intuitive display of relevant technical and subjective parameters of immersive signals in a fast and intuitive way

Keep an eye on the overall surround image balance on both Main and Upper beds

Monitor the relationship between the two layers

Identify phase problems to make sure your audio will down mix correctly

Check stereo width and perceived position between each channel pair

Check the level according to SPL or loudness measures

Identify center channel issues

Be warned if the LFE channel has correlation problems

Technically SpokenWhat is required to run ISA?

RTW TouchMonitor TM7 or TM9 with software version 8 or higher

Software license SW20001 Multichannel Mode

Software license SW20002 Loudness and SPL Display

Software license SW20004 SSA - Surround Sound Analyzer

Software license SW20015 SSA - Immersive Sound Analyzer

ISA - Immersive Sound Analyzer Features

Designed for Immersive audio formats based on 5.1 or 7.1 main beds and 2.0 or 4.0 upper beds

Graphical display indicating single channel and total program loudness (Total Volume Indicator)

Position and width of phantom sound sources (PSI) in Main- and Upper Beds

Phase Correlation between adjacent channels

Separate correlators for the outer adjacent channels

Subjectively perceived acoustic focal point with the Dominance Indicator (DMI) for both Main- and Upper Beds

Subjectively perceived acoustic focal point in the complete immersive area with the Immersive Dominance Indicator (IDI)

LFE Phase warning (warns in case of negative correlation between any channel and LFE)

Formats Supported: 5.1.2, 5.1.4, 7.1.2, 7.1.4

in RTW Knowledge Base

LINK:	https://www.rtw.com/blog/welcome-to-our-blog-1/focus-the-immersive-sou...
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