Gating Automatic Mic Mixer

Alright, let’s swap from the Gain-Sharing Automatic Mixer to the Gating Automatic Mic Mixer.

You’ll find it back in the Schematic Library under Audio Components and Mixers.

You’ll notice that mine is listed as BETA, because this is a newly-renovated component in Designer version 4.2.

If you’re using a newer version of the software it won’t say BETA,

but it should operate in the same ways. The main goal of the Gating Automatic Mic Mixer is to open

or close its incoming channels based on whether or not they reach a certain threshold.

Basically, if someone is speaking into a microphone a channel should gate open,

and if not then the channel should gate closed. Its properties are similar to the Gain-Sharing Automixer

I’m going to change its channel count to 4, I have the option to use a Mix Only output,

direct Channel outputs, or both, and I can activate the Side-Chain Filter

that fine-tunes the type of audio that the Mixer listens for on each channel.

I’m going to connect this to my design, but I actually can’t use the same

pink-noise generators I used in the last video.

You see, one of the benefits of the Gating Automatic Mic Mixer is its Noise Floor Tracking.

This mixer tracks the steady or slowly-changing background noise of a room such as air conditioning,

and adjusts the threshold required for each channel to open relative to this slowly changing noise floor.

Without this, a noisy air conditioner might open every microphone channel,

or when the air conditioning turns off a person might have to speak louder

in order to still reach the open threshold. Noise Floor Tracking takes care of all of this. But for my example,

I can’t use those pink-noise generators anymore because the Mixer will think

that the steady pink noise is background noise, and nothing will work.

So instead I’ve changed John, Paul, George and Ringo into

Audio Players that are looping some prerecorded vocal tracks:

"Hello, I’m John."

"Hello, I’m Ringo."

Let’s double-click the Mixer to look at its Control Panel,

and let’s take a look at each section from left to right. First we have the Side-Chain Filter,

which we activated in the properties panel, and we can adjust what aspect of each channel

is being analyzed to determine if it reaches its open threshold.

By default a High-Pass filter is active since we’re generally listening for human voices,

but you could change this however you like.

Remember, this is not applying a high-pass filter to the channels,

it only selects what audio spectrum is being analyzed, without actually affecting the channel at all.

Next is the Gate section, which determines how the channels are opened.

The most important knob here is the "Threshold Level Above Noise" knob.

This is how loud a channel must be – above the Noise Floor – in order for it to be gated open.

If it does not reach this threshold, then it is attenuated by the amount of the Depth knob,

to keep those closed channels silent.

The Hold Time determines how long a channel will remain open

after it stops reaching the threshold before it is closed. You could increase this time to

make sure that a gate won’t close just because someone takes a lot of long pauses in their sentences.

If no channels are gated open, you could activate the "Last Mic On"

option which will keep the last open channel active.

This is useful for keeping a small amount of room noise alive

in the signal rather than cutting to total silence between speakers.

The middle section gives you control over each individual Channel,

of which we have four. At the bottom you could label them appropriately.

The meter in the middle shows you the "Signal Level Above Noise,"

or how loud each channel is over the Noise Floor. If this level is equal to or greater than the Threshold level,

then the channel will be gated open, and the Open LED at the top will illuminate to show that it is open.

You could nominate one channel as the Default channel, which will stay open when no channels are open.

This is mutually exclusive with the "Last Mic On" option: either you can have the last mic stay open,

or you could have a Default channel stay open,

so you’ll see that activating either option deactivates the other.

You can also manually force a channel to open by selecting the "Manual" button.

At the bottom of this section you can mute or adjust the gain of each channel

keep in mind that this is post-gating,

so raising the gain here will not increase a channel’s ability to reach its threshold.

The next section is the Number of Open Mics. Nom. NOM NOM NOM.

Like the Gain-Sharing Mixer, this mixer will attenuate channels when many are open at a time,

based on the settings here. Every time the number of open mics doubles,

one attenuation step will be applied to all channels.

So by these default settings, when we go from one open mic to two open mics,

each will be attenuated by 3 decibels. If we go from two open mics to four open mics,

each will be attenuated by 6 decibels, or two steps.

You can set a maximum attenuation that will cap these steps here.

If you activate Linear Attenuation, one attenuation step will be applied every time

a new channel opens rather than every time the NOM doubles.

You can keep track of how many channels are currently open

and the amount of attenuation applied to them here on the right.

You should note that any channels opened manually do not count towards the NOM.

This attenuation is applied to all of the component’s output channels.

In some scenarios, you may not wish to apply this attenuation to the direct channel output pins,

particularly if you are recording individual channels for archive purposes

you wouldn’t want the volume of that recording to randomly fluctuate

based on other channels that aren’t part of the recording.

If you deactivate the "Direct Outs NOMS Attenuation" button,

the direct channel output pins will keep their natural level.

You can also lower the maximum allowable number of open mics if you want to

limit the number of channels that can be open at a time.

If more channels are reaching their threshold than are allowed to be open by this field,

then the channel that has been open the longest will gate closed.

Finally, all that’s left is a master Mute and Gain fader for the "Mix" output pin.

The only thing left to mention is that the Gating Automixer incorporates a feature called "ID Gating,"

which determines which channel is the primary source of audio that is detected on multiple channels.

For instance, if a loud talker yells so loudly that he is picked up on multiple microphones

and reaches the threshold on all of them, the Mixer is smart enough to know to only open the channel

where he’s loudest, since this is the closest one to him.

That’s it for the Gating Automatic Mix Mixer. Thanks for watching, and we’ll see you next time.