2. Autodirective Dual Microphone Digital Signal Processing technology to build an optimal directional microphone Presented by Alexander Goldin Copyright © 2003 Alango Ltd.

3. 2 Common microphone types Omnidirectional Hyper-cardioidSuper-cardioid Bi-directional (figure eight) Bi-directional (dB plot) Cardioid = Distance factor = 1 Distance factor = 1.7 Distance factor = 2.0 Distance factor = 1.9 Distance factor = 1.7 Null

4. 3 The Optimal Directivity Microphone Ability: automatically change the directivity pattern Objective: the best signal-to-noise ratio in varying acoustic conditions. Challenge: Fast adaptation with minimal distortion

5. 4 Electronic Directional Microphone Normalized polar pattern as a function of (fixed frequency) Delay EQ(, )

6. 5 Autodirective Dual Microphone Autodirective Dual Microphone schematic DSP based dual microphoneDual microphone with variable polar pattern Delay EQ(, ) 1.Divide both channels on subbands 2.Create an optimal microphone in every frequency band 3.Equalize every band 4.Combine from bands

7. 6 Adaptive Directivity Block Adaptive Directivity Block schematic 1.Estimate sensor difference (gain s) 2.Define the optimal delay 2.Define the optimal delay 3.Compute equalization gain g according to and ; Autodirective Dual Microphone schematic ADB functionality:

8. 7 Measured ADM polar pattern

9. 8 ADM and other Alango technologies Additional Processing Noise Suppression Noise Suppression Multiband Dynamic Range Reduction Multiband Dynamic Range Reduction Automatic Gain Control Automatic Gain Control Other Alango technologies use the same subband decomposition scheme. Integration of technologies is easy without extra MIPS, Memory or time delay required.

10. 9 ADM: summary of virtues An optimal, adaptive polar pattern with a very low adaptation time (around 5ms) An optimal, adaptive polar pattern with a very low adaptation time (around 5ms) Far and close talk operations Far and close talk operations Low latency (<5ms) Low latency (<5ms) No proximity effect No proximity effect Low sensitivity to wind and other turbulences Low sensitivity to wind and other turbulences Easy integration with other Alango technologies Easy integration with other Alango technologies Low demands to constituting SPL sensors Low demands to constituting SPL sensors Easy integration into mobile and other devices Easy integration into mobile and other devices

11. 10 ADM applications Cellular Phones ADM is perfect for cellular phones. ADM technology significantly improves signal quality for both speakerphone (far-talk) and handset (close-talk) phone usage. Mic.2 Mic.1 Hearing aids Hearing aids ADM works very well in hearing aids. It provides high attenuation of ambient noise and other off-axis sounds. Mic.1Mic.2 Reporters microphone ADM excellent and adaptive directivity combined with its immunity to wind noise makes it ideal technology for such application. Conference microphone ADM excellent directivity, lack of proximity effect and low sensitivity to popping and puffing sounds eliminates most of conference microphone problems. Mic.2 Mic.1 Hands-free car kits Hands-free car kits ADM high directivity, immunity to wind noise and low components cost provides provides unparallel benefits

12. 11 ADM in cellular phones Outside BOS (regular mic) In the close-talk (handset ) mode, ADM creates Bubble Of Sensitivity (BOS) muting outside sounds ADM Microphones Inside BOS (ADM) Beam Of Sensitivity (BOS) In the far-talk (speakerphone ) mode, ADM creates Beam Of Sensitivity (BOS) attenuating outside sounds Outside BOS (regular mic) Inside BOS (ADM)

13. 12 Alango contact information www.alango.com Headquarters: Edgar 1, Tirat-Carmel 39100, Israel Telephone: +972 4 8580743 Fax: +972 4 8580621 e-mail: sound.info@alango.comsound.info@alango.com