Acoustic echo cancellation and speech enhancement module for hands-free applications
Digital speech offers integrated solution Speech Enhancement for hands-free system. Speech enhancement module is intended for resolving the following hands-free system problems:
Acoustic Echo is caused by acoustic coupling between loudspeaker and microphone. If communication line between two remote hands-free participants has little delay (less 30 ms), then acoustic echo don't create any problem during conversation, because active participant can't hear his echo. But if propagation delay is significant then acoustic echo becomes annoying. This problem is very important for modern digital communication systems (VoIP systems, VoP systems, mobile phones, 3G phones), because significant processing and algorithmic delay in such systems.
If speech enhancement system is used in car kits, laptop softphones and mobile phones or in other similar applications then background noise can significantly decrease voice quality. So modern speech enhancement system working in such conditions should increase signal noise ratio for final voice quality improving.
Different loudness of terminal equipment.
Modern hands-free terminals should connected to very different remote terminal equipment, which have different loudness. We can get very quiet sound from loudspeaker when remote terminals transfers very quiet signal, and we can hear very distorted, clipped signal in otherwise. This problem is especially important for PC softphone, because in this case microphone and speakers don't intend for telecommunication.
Howling sound (Larsen effect).
Howling sound occurs in hands free communication system with high positive feedback. In these systems signal received by the microphone is amplified and passed to the loudspeaker as echo from remote hands free system. The sound from the loudspeaker can then be received by the microphone again, amplified further, and then passed out through the loudspeaker again.
Digital Speech offers Speech enhancement modules for the following applications
This Speech Enhancement module is intended for application, which use microphone and loudspeaker with fixed location, for example: mobile phones, smartphones, dual-phones, 3G phones, two wire telephones, IP phones, payphones and so on.
Speech Enhancement module is intended for application, which use microphone and loudspeaker with arbitrary location, for example chips for mobile phones (GSM , 3G phones), set top box, car kits, intercoms and so on.
Speech Enhancement module is intended for PC and mobile softphones
Speech enhancement flow chart
Speech enhancement components: