wideband speech communications: the good, the bad, and the ugly
DESCRIPTION
Wideband Speech Communications: the Good, the Bad, and the Ugly. Scott Pennock Sr. Hands-Free Standards Specialist QNX Software Systems (Wavemakers). Outline. Introduction The Good The Bad The Ugly Conclusions. Introduction. What is wideband (WB) speech? - PowerPoint PPT PresentationTRANSCRIPT
The Fully Networked Car Geneva, 4-5 March 2009
1
Wideband Speech Communications: the Good, the Bad, and the Ugly
Scott PennockSr. Hands-Free Standards Specialist
QNX Software Systems (Wavemakers)
The Fully Networked Car Geneva, 4-5 March 2009
2Outline
o Introductiono The Goodo The Bado The Uglyo Conclusions
The Fully Networked Car Geneva, 4-5 March 2009
3Introduction
o What is wideband (WB) speech?• Speech has energy from around 50-10000Hz• Traditional narrowband (NB) terminals and
networks bandlimit speech down to around 300-3400Hz
• WB speech in this presentation refers to a bandwidth of 50-7000Hz
o Why is WB speech important to automotive?• More robust to vehicle noise• Reduces driver distraction• Helps enable spatial auditory displays
o This presentation will review the benefits, challenges, and unresolved issues with WB speech in an automotive environment
The Fully Networked Car Geneva, 4-5 March 2009
4The “Good”
o Improves task performance• Better speech comprehension• Reduced driver distraction• Improved talker identification• Better speech localization• Other potential task improvements
o Preferred by users• Higher quality• Less listening-effort• More comfortable loudness-level• Other factors influencing preference
o Task performance benefits alone make a compelling argument for deploying WB speech in the vehicle
The Fully Networked Car Geneva, 4-5 March 2009
5WB speech provides extra frequency and temporal information
This “difference spectrogram” was calculated by subtracting the NB from WB spectrogram of someone saying “the juice of lemons makes fine punch”.
The Fully Networked Car Geneva, 4-5 March 2009
6WB speech increases intelligibility and is more robust to vehicle noise
3.3 kHz 5 kHz 7 kHzCUTOFF FREQUENCY
0.5
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0.7
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0.9
1.0P
rob(
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RR
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SNR=24 dBSNR=12 dBSNR = 0 dB
s (e.g. six) mistaken for f (e.g. fix)
90% CI
Confuse_s_f
Probability of correct response by bandwidth and SNR
The Fully Networked Car Geneva, 4-5 March 2009
7WB speech improves speech comprehension and reduces driver distraction
This figure illustrates auditory streaming of speech. Shapes represent phonetic units that have been recognized. Dotted lines show information that would be missing without wideband speech.
The Fully Networked Car Geneva, 4-5 March 2009
8The “Bad”
o Users are more sensitive to WB echo and noise due to perceptual effects• Ear is most sensitive to high frequency region of
WB speech• Loudness of echo and noise in new frequency
regions will add to loudness in narrowband region• High frequency echo is not masked as effectively
by one’s own voiceo Acoustic Echo Cancellers (AEC) have a more
difficult time removing high frequency echo• Poor excitation signal makes it harder to drive
echo canceller to convergence• High frequency distortion is falsely classified as
driver’s speech and can prevent AEC from training
The Fully Networked Car Geneva, 4-5 March 2009
9The challenges presented by WB speech can be addressed
o Good electro-acoustic design of vehicle platforms• Careful acoustic design of vehicle cabin• Proper selection, placement, orientation, and
mounting of microphones and loudspeakers• High quality signal transport (e.g., optical,
differential)o High performance speech enhancement algorithms
• AEC• Noise Reduction (NR)• Low-complexity compression for devices with limited
resources
The Fully Networked Car Geneva, 4-5 March 2009
10The “Ugly”
o Interoperability issues• WB terminal users will experience
inconsistent loudness and quality• NB terminal users will become less
satisfied with quality because of exposure to WB speech
o Long transition period
The Fully Networked Car Geneva, 4-5 March 2009
11Users of WB terminals will experience inconsistent loudness and quality
o Solution for inconsistent loudness is to use Receive Automatic Gain Control (AGC) based on perceived loudness instead of RMS or peak levels
o Differences in quality can be reduced by using BandWidth Extension (BWE) and High Frequency Encoding (HFE) techniques
The Fully Networked Car Geneva, 4-5 March 2009
12There will be a long transition period
o Deployment has already started o Not clear when WB speech will take-off, but
automotive is already well positioned• Vehicle Audio Systems are currently wideband
capable• WB microphones available and easy to drop-in• Several WB speech coders are already standardized
o Even after WB speech takes hold, hybrid WB/NB connections will be around for a long time• NB network equipment and terminals are built to last • Continued use in certain areas
The Fully Networked Car Geneva, 4-5 March 2009
13Conclusions
o WB speech improves task performanceo Users prefer WB speecho WB speech is important to automotive
• More robust to vehicle noise• Reduces driver distraction• Helps enable spatial auditory displays
o WB speech will be a key differentiator for automotive OEMs and service providers
The Fully Networked Car Geneva, 4-5 March 2009
14Conclusions (continued)
o Successful automotive deployment depends on:• Attention to the design of vehicle platforms• High performance speech enhancement
algorithms (e.g., AEC, NR, etc.)o Interoperability issues will eventually get
worked outo NB network equipment/terminals will be in
use in certain areas for a long time