Introduction
1
Alero 8-Channel Microphone Mixer Instruction Manual
Introduction
The Alero (FG1140-08) is an 8 channel microphone mixer with built in acoustic echo canceller. Alero acts as a USB audio device
with a capability to connect 3 analog input and 3 analog output channels. Alero also supports 2 channel mono line level speaker
signal outputs:
Line In 1 and 2 are stereo
Line Level to speaker is stereo
Audio
The product contains audio signal processing software with the following signal processing blocks:
Alero supplies full duplex communication without disturbing background noise in a telecommunication system. The microphone
input channels are automatically mixed with the AMM. The loudspeaker echo is removed from the microphone signals by the
modules AEC and RES. Noise reduction, equalization filters are applied to further improve audio quality. Comfort noise is added to
microphone channels to avoid a pumping noise level when the RES is working.
A flowchart of the signal processing modules for the microphone input is shown in FIG. 1.
After the microphone inputs have been mixed to one output it will be added to output channels in combination with input channels,
see Figure 2.
Processor
Description
Automatic Microphone
Mixing (AMM)
The microphone input channels are automatically combined into one output channel. The
microphone mixing performs a selection of which channel to open, reducing overall noise level
and improving speech clarity compared with just adding all microphone channels.
Acoustic Echo Cancellation
(AEC)
Models the acoustic environment and removes the loudspeaker echo via adaptive filtering.
Residual Echo Suppression
(RES)
Additional suppression of acoustic echo while still maintaining full duplex performance.
Comfort Noise (CN)
Noise with similar level and characteristics as the background noise is added to microphone
channels to avoid a pumping noise level when the RES applies damping to reduce echoes.
Noise Reduction (NR)
Models the characteristics and level of the background noise and reduces the noise level on the
microphone channels.
Channel Equalization (EQ)
Equalization filtering is applied for enhancing speech clarity and to compensate for
characteristics on connected devices.
Signal Mixer
The processed microphone signal is added to the output channels in combination with the input
channels. It is possible to select the routing of input channels to output channels.
Volume Adjustment (VOL)
Volume adjustment and mute functionality for all input and output channels without sudden
transitions. There are no artifacts such as clicks and pops when muting/unmuting a channel.
Signal amplification is performed without introducing amplitude clipping.
FIG. 1
Microphone Signal Processing Flowchart