Acoustic Echo Canceler Component

The Q‐Sys multi‐channel Acoustic Echo Canceling (AEC) component is used in conference rooms (Near-End) and other installations where people call in from remote locations. The remote caller’s (Far-End caller's) voice is broadcast over loudspeakers in the conference room. The sound is picked up by microphones in the conference room and echoed back to the Far-End caller. The purpose of the AEC is to eliminate these echoes while at the same time allowing the Far-End caller to hear clearly, what people in the room are saying.

Each microphone in the conference room is plugged into one channel of the Q-SYS AEC component. Each channel also receives the loudspeaker signal that carries the remote talker’s voice. This is called the AEC reference signal. To remove the echoes, the AEC subtracts a filtered version of the reference signal from the microphone signal.

Most modern AEC systems, including Q-SYS AEC, process the signal in many narrow frequency bands. This introduces a delay in the signal. The Q-SYS AEC latency is 13.3 milliseconds.

For detailed information about Acoustic Echo Canceling, read the QSC White Paper.

IMPORTANT - AEC Best Practices

Connections

Inputs

Outputs

Reinforcement Channel (optional) - Output to the Near-End conference room loudspeakers

Controls

AEC

Control	Function	Default/Range
Bypass	Bypasses the AEC function when activated.	Off/On
Echo Return Loss Enhancement Reduction Meter	Echo Return Loss Enhancement (ERLE) - This measures how much, in dB, the Far-End echo arriving at the Near-End microphone is attenuated by the AEC system once the AEC has converged. The ERLE meter is used to indicate how effective the AEC is in terms of suppressing the acoustic echo. A reading below 10 dB may indicate that the room tail is longer than the AEC tail property. Readings above 20 dB indicate that the AEC is working properly.	N/A

Noise Reduction

Control	Function	Default/Range
Noise Reduction Enable	Enables and disables the noise reduction functionality of the AEC.	Enable/Disabled
Amount dB	The purpose of Noise Reduction is to reduce the level of relatively steady state noises like fans, lawn mowers, wind, 60 Hz electrical hum. The goal is to reduce these noises without affecting the desired speech. The Amount control determines how aggressive the Noise Reduction is in eliminating these steady-state noises. The more you turn it up, the more aggressively the AEC removes the noise at the expense of distorting the Near-End microphone signal.	Default = 20.0 Range = 0.0 to 24.0

Comfort Noise

Control	Function	Default/Range
Comfort Noise Enable	Enables and disables the comfort noise functionality of the AEC.	Enable/Disabled
Level dB	Adjust this level, when the room is completely quiet, to a level that would indicate a "connected" phone line to the Far-End caller.	Default = -53.0 Range = -100.0 to -20.0

Properties

Acoustic Echo Canceler

Property	Function	Choices
Tail Length ms	Tail length is the maximum room impulse response that the adaptive filter can model. Typically, you would use 200 ms, but for exceptionally reverberant rooms, you may want to use 400 ms. When the Tail Length is set to 400 ms, the channel count is doubled when calculating AEC Processing in Check Design (Shift+F6), which effectively cuts the number of available channels in half.	100 200 400
Reinforcement Output	Select Yes to make the Reinforcement Output pin available, or No to hide it. No is the default.	No / Yes

Channels

Property	Function	Choices
Channel Count	Selects the number of input channels available for the AEC. Each Core has a set limit of channels you can use in a design. Note that an AEC channel with a Tail Length of 200ms requires double the processing of one with a Tail Length of 100ms. Likewise, an AEC channel with a Tale Length of 400ms requires four times the processing of one with a Tail Length of 100ms.	1 to 256

NOTE: The numbers in red below indicate new values for Q-SYS Designer release 5.0.

Core Model	AEC Channels
Tail Length	100 ms	200 ms	400 ms
110f	16	16	8
250i	60	40	20
500i	48	32	16
1000	24	12	6
1100	144	96	48
3000	72	36	18
3100	288	192	96
4000	72	36	18

Pin Name	Value	String	Position	Pins Available
AEC Bypass	0 1	active bypass	0 1	Input / Output
Comfort Noise Enable	0 1	disabled enabled	0 1	Input / Output
Comfort Noise Level	-100.0 to -20.0	-100.0 dB to -20.0 dB	0.000 to 1.00	Input / Output
Echo Return Loss Enhancement	0 to 30	0 dB to 30 dB	0.000 to 1.00	Output
Noise Reduction Amount	0.0 to 24.0	0.0 dB to 24.0 dB	0.000 to 1.00	Input / Output
Noise Reduction Enable	0 1	disabled enabled	0 1	Input / Output