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Solutions for mobile phones and voice terminals

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Voice communication solutions

Alango has developed a rich portfolio of digital signal processing technologies answering all current needs of front-end voice enhancement in advanced mobile phones and voice terminals. The technologies are seamlessly integrated into one Voice Communication Package (VCP) sharing memory and computational blocks to lower device power consumption. VCP has a clearly defined, industry proven API interface and it is easily integrated into existing mobile phone software architectures. Highly optimized VCP versions exist for several popular DSP platforms including ARM cores.

In its maximal configuration VCP currently includes:

  1. Adaptive dual microphone (handset and speakerphone modes)
  2. Acoustic echo cancellation (handset and speakerphone modes)
  3. Noise suppression (stationary and transient on microphone and speaker channels)
  4. Automatic microphone gain control and dynamic range compression (handset and speakerphone modes)
  5. Automatic speaker volume and equalization control (ambient noise dependent)
  6. 32 band static equalizer (microphone and speaker channels)

Cellular Phones Call Quality Comparison

Our comparison of modern phones noise cancelling capabilities:

Far-Field Smartphone Voice Recognition Enhancement

Far-field voice activated and controlled devices are becoming quite popular.  Alango has developed multi-microphone array technology allowing this functionality to be implemented in a smartphone with 2~4 microphones.  Alango’s Voice Enhancement Package employs n-Mic beamforming to optimize voice pickup and transform the smartphone into a voice activated hub with excellent voice recognition performance.

Presentation “Improvement of Voice Trigger Recognition in Smartphones”
Download PPSM version (PowerPoint slide show)
Download PDF version

Music and entertainment solutions

In a mobile world phones are often used as music players, MP4 players or gaming consoles in places where noise level and spectrum change quick and in a wide range (street, metro, train, bus). Alango has developed a unique Automatic Volume and eQualization control technology for Music and Entertainment (AVQ-Me) enhancing mobile phone user’s experience in such dynamically changing noisy conditions.

Stereo Sound Recording Solutions For Mobile Environment

Recording of high quality stereo sound with a mobile phone is problematic. Even if two phone microphones are used, the distance between the microphones is too small to provide sufficient stereo separation between the left and right channels. The sound of video recording comes mono or with confused spatial separation.

Alango has developed special (2, 3, 4) microphone technology of Adaptive Directional Microphones (ADM) that uses signals from built-in omnidirectional microphones and according to phase difference, and programmed parameters enhances sounds coming from left (left channel) or right (right channel) angular directions. Alango ADM technology provides high quality, true stereo recording attenuating sounds outside the camera view.

Presentation of Practical DSP Solution for Mobile Phone Stereo Sound Recording (pptx)

Voice Processing Technologies for mobile phones

Adaptive Dual Microphone (advanced technology)

Alango Adaptive Dual Microphone (ADM) technology is a technology that dramatically reduces all types of ambient noises. Adding the second microphone plus ADM technology to a mobile phone or voice terminal enables efficient voice communication in extremely noisy conditions such as train stations, noisy restaurants, discotheques etc. ADM is indispensable for professional communication in emergency situations with lots of people talking around as well as other sounds (sirens, explosions, etc).

Automatic speaker volume and equalization (advanced technology)

Automatic Volume and eQualization control for Voice (AVQ-V) is an advanced technology that automatically adjusts the loudspeaker sound according to the ambient noise.

Acoustic Echo Cancellation

Alango Acoustic Echo Cancellation has been designed to provide full-duplex speakerphone and handset capabilities to mobile voice terminals.

Noise suppression

Microphone noise suppression technology is an indispensable part of signal processing chain in a modern mobile phone. Alango VCP package adds speaker channel noise suppression improving user’s listening experience when the other party speaks from noisy conditions.

Characterizations of Alango single channel noise suppression technology

Automatic microphone gain control

Fast and noise robust automatic gain control is one of the key features of a good mobile phone or voice terminal. According to a low of acoustics in a free field, changes in the microphone signal amplitude are inversely proportional to the changes in distance between the microphone and the sound source (user’s mouth). As such, automatic gain control is extremely important in both handset and speakerphone modes of mobile phone operation.

In the handset mode the relative distance between user’s mouth and the microphone may change very fast. Small, unnoticeable to the user movement of the phone holding hand may change the distance from 1 to 5 centimeters (0.4-2 inches) in a fraction of a second. This means 5 times or 14dB changes in the signal amplitude. Obviously, such changes must be compensated; otherwise the transmitted speech will be too weak on the other side. Most existing solutions employ strong Dynamic Range Compression (DRC) of loud signals (from close distances). Simply, the louder the user speaks the more his voice signal amplitude is reduced (compressed). This causes flattening user’s voice signal level. However, since far sounds (noises) are not compressed, this causes significant worsening of the signal-to-noise ratio. This artificial degradation of signal-to-noise ratio caused by compression is one of the main reasons why distant noises often sound as loud as user’s voice however loud and close to the microphone he or she speaks.

 

 

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