User Manual

BM62/64
Preliminary
 2017 Microchip Technology Inc.
DS60001403C-Page 15
2.0 AUDIO
The input and output audios have different stages and
each stage can be programmed to vary the gain
response characteristics. For microphone, both sin-
gle-ended inputs and differential inputs are supported.
To maintain a high quality signal, a stable bias voltage
source to the condenser microphone’s FET is provided.
The DC blocking capacitors can be used at both posi-
tive and negative sides of a input. Internally, this analog
signal is converted to 16-bit, 8/16 kHz linear PCM data.
2.1 Digital Signal Processor
A Digital Signal Processor (DSP) is used to perform
speech and audio processing. The advanced speech
features, such as acoustic echo cancellation and noise
reduction are inbuilt. To reduce nonlinear distortion and
to help echo cancellation, an outgoing signal level to
the speaker is monitored and adjusted to avoid satura-
tion of speaker output or microphone input. Adaptive fil-
tering is also applied to track the echo path impulse in
response to provide echo free and full-duplex user
experience.
The embedded noise reduction algorithm helps to
extract clean speech signals from the noisy inputs cap-
tured by the microphones and improves mutual under-
standing in communication.
The advanced audio features, such as multi-band
dynamic range control, parametric multi-band equal-
izer, audio widening and virtual bass are inbuilt. The
audio effect algorithms improve the user’s audio listen-
ing experience in terms of better audio quality after
audio signal processing.
Figure 2-1 and Figure 2-2 illustrate the processing flow
of speaker-phone applications for speech and audio
signal processing.
FIGURE 2-1: SPEECH SIGNAL PROCESSING
FIGURE 2-2: AUDIO SIGNAL PROCESSING