Acoustic Echo Canceler

The Q‐SYS multi‐channel Acoustic Echo Canceler (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.

For more about AEC, see:

Core Processing

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 input-to-conference-output delay or latency is 32 milliseconds for the Core 110f and 26.7 milliseconds for all other Cores. Likewise, the Q-SYS AEC input-to-reinforcement-output delay or latency is 21.4 milliseconds for the Core 110f and 10.7 milliseconds for all other Cores.

Max AEC Channels per Core by Tail Length

Tail Length >	100 ms	200 ms	300 ms	400 ms
Core 110f	24	16	12	8
Core 250i	48	32	24	16
Core 500i	32	24	16	16
Core 510i	96	64	48	32
Core 1100	96	72	48	24
Core 3100	192	144	96	48
Core 5200	240	160	120	80

Properties

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.	100 200 300 400
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 512
Shared Reference	Select Yes to have one input Reference signal shared by all channels.	Yes / No
Reinforcement Output	Select Yes to make the Reinforcement Output pin available, or No to hide it. No is the default.	No / Yes
Max Noise Reduction	Select the maximum level of noise reduction allowed with the Noise Reduction (NR) control. Note: In most cases, this should be left at the default of 10dB to avoid distorting sound quality.	10dB 20dB 30dB

Controls

Canceler

Control	Function	Default / Range
Echo Return Loss Enhancement (ERLE)	This meter indicates how much, in dB, the Far-End echo arriving at the Near-End microphone is attenuated by the AEC adaptive filter once the filter 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 during Far-End only talk may indicate that the room tail is longer than the AEC tail property. Readings above 20 dB during Far-End only talk indicate that the AEC is working properly.	N/A
Bypass	Bypasses the AEC function, including its latency, when activated.	Default = Off Off / On
Reference-to-Microphone Level Ratio (RMLR)	This meter indicates how much, in dB, the Far-End reference signal level exceeds the Near-End microphone signal level. The RMLR meter is used to adjust the reference signal level during Far-End only talk. In general, the Far-End reference signal level should approximately equal the Near-End microphone signal level, as indicated by a ratio of 0dB. The ratio can be adjusted using the Reference Gain knob.	-20 to 10
Target 0dB	Adjust the Reference Gain until the RMLR is at the target of 0dB.	N/A
Reference Gain	This knob adjusts, in dB, the Far-End reference signal level. In general, the Far-End reference signal level should approximately equal the Near-End microphone signal level, as indicated by 0dB on the Reference-to-Microphone Level Ratio meter.	Default = 0 Range = -40 to 0

Adaptive Filter

Control	Function	Default / Range
Hold If Mic Level Below	Sets the threshold, in dB, when AEC adaptation stops. In most cases, the microphone signal will be nonexistent when the mic's mute feature is activated, so this level should be left at the default of -100 dB. However, if your microphone only strongly attenuates the signal when muted, this weak signal can cause issues with AEC adaptation. In this case, try adjusting the Hold level to just above the level when the mic is muted. For example, if your microphone signal is -80 dB when the mute feature is activated, try adjusting the Hold level to -60 dB.	Default = -100dB Range = -100 to 0

Control

Function

Default / Range

Hold If Mic Level Below

Sets the threshold, in dB, when AEC adaptation stops.

In most cases, the microphone signal will be nonexistent when the mic's mute feature is activated, so this level should be left at the default of -100 dB. However, if your microphone only strongly attenuates the signal when muted, this weak signal can cause issues with AEC adaptation. In this case, try adjusting the Hold level to just above the level when the mic is muted.

For example, if your microphone signal is -80 dB when the mute feature is activated, try adjusting the Hold level to -60 dB.

Default = -100dB

Range = -100 to 0

Post-Processor

Control	Function	Default / Range
Residual Echo Suppression (RES) %	Residual Echo Suppression applies additional suppression to any residual echo that was not removed by the adaptive filter and echo reduction functions of the AEC component. This control determines how much any residual echo is suppressed. The more you turn it up, the more aggressively the residual echo is suppressed at the expense of distorting the Near-End microphone signal.	Default = 50.0 Range = 0 to 100
RES Enable	Enables and disables Residual Echo Suppression functionality of the AEC.	Default = Enabled Enabled / Disabled
Noise Reduction (NR) dB	Noise Reduction reduces the level of relatively steady state noises like fans, lawn mowers, wind, and mains electrical hum. The goal is to reduce these noises without affecting the desired speech. This control determines how much, in dB, these steady-state noises are reduced. The more you turn it up, the more aggressively the noise is removed at the expense of distorting the Near-End microphone signal.	Default = 6.00 Range¹ = 0.0 to 30.0
NR Enable	Enables and disables the noise reduction functionality of the AEC.	Default = Enabled Enabled / Disabled
1. The range depends on the Max Noise Reduction property.

Control Pins

Pin Name	Value	String	Position	Pins Available
For Each Channel
AEC Bypass	0 1	no bypassed	0 1	Input / Output
Echo Return Loss Enhancement	0 to 20	0 dB to 20 dB	0 1	Output
Hold If Microphone Level Below	-100 to 0	-100dB to 0dB	0.000 to 1.00	Input / Output
Reference Gain	-40 to 0	-40dB to 0dB	0.00 to 1.00	Input / Output
Reference-to-Microphone Level Ratio	-20 to 10	-20 dB to 10 dB	0 1	Output
For Component
Noise Reduction	0.0 to 30.0	0 dB to 30.0 dB	0.000 to 1.00	Input / Output
Noise Reduction Enable	0 1	disabled enabled	0 1	Input / Output
Residual Echo Suppression	0 to 100	0% to 100%	0.000 to 1.00	Input / Output
Residual Echo Suppression Enable	1 0	enabled disabled	1 0	Input / Output

Acoustic Echo Canceler

Max AEC Channels per Core by Tail Length

Inputs

Outputs

1. The range depends on the Max Noise Reduction property.

For Each Channel

For Component