advanced noise reduction for mobile telephony (1)

ADVANCED NOISE ADVANCED NOISE REDUCTION FOR REDUCTION FOR

MOBILE TELEPHONYMOBILE TELEPHONY

OUT LINEOUT LINE1.1. IntroductionIntroduction2.2. A phone audio pathwayA phone audio pathway3.3. Effect of noiseEffect of noise4.4. Type of noiseType of noise5.5. Present noise reduction techniquePresent noise reduction technique6.6. Advanced noise reduction techniqueAdvanced noise reduction technique7.7. TechnologyTechnology8.8. Processes in voice processorsProcesses in voice processors9.9. Fast cochlea transformsFast cochlea transforms10.10. Fct VS FFTFct VS FFT11.11. CharacterizationCharacterization12.12. Grouping & selectingGrouping & selecting13.13. Inverse Fast cochlea transformsInverse Fast cochlea transforms14.14. AdvantagesAdvantages15.15. conclusionconclusion

INTRODUCTIONINTRODUCTION

• Have you ever used your mobile phone to place a call Have you ever used your mobile phone to place a call from a noisy place and been asked to call back from from a noisy place and been asked to call back from someplace quieter?someplace quieter?

• It would be great if the phone would mute the It would be great if the phone would mute the

background noise for youbackground noise for you

• This can be done by advanced multi microphone This can be done by advanced multi microphone noise suppression algorithm working with principle noise suppression algorithm working with principle of human hearing system.of human hearing system.

A PHONE AUDIO PATHWAYA PHONE AUDIO PATHWAY

This works good if no noise

EFFECT OF NOISEEFFECT OF NOISE

If the environment is noisyIf the environment is noisy

It will enter into microphone so that it become It will enter into microphone so that it become difficult for the person on the other end of call to difficult for the person on the other end of call to understand.understand.

Voice encoder transmit unnecessary voice, so Voice encoder transmit unnecessary voice, so wastage of energy.wastage of energy.

TYPES OF NOISETYPES OF NOISE

Basically three types:Basically three types:1.1. Stationary noise: Stationary noise: Does not contain rapid Does not contain rapid

changes eg: steady sound of a fan.changes eg: steady sound of a fan.

2.2. Non stationary noise: Non stationary noise: rapid changesrapid changes

eg: music containing drums.eg: music containing drums.

3.3. Quasi stationary noise: Quasi stationary noise: stationary for a stationary for a particular time eg: steady babble of a crowdparticular time eg: steady babble of a crowd

PRESENT NOISE REDUCTION PRESENT NOISE REDUCTION TECHNIQUETECHNIQUE

Fast Fourier Transform: Fast Fourier Transform: • Removes noise which is stationary or Removes noise which is stationary or

quasi stationary.quasi stationary.• But fails to remove non stationary But fails to remove non stationary

noise, because these noise changes too noise, because these noise changes too fast and are similar to the desired noise.fast and are similar to the desired noise.

• Fast Cochlea TransformFast Cochlea Transform

ADVANCED NOISE REDUCTION ADVANCED NOISE REDUCTION TECHNIQUETECHNIQUE

Based on the principle of human auditory Based on the principle of human auditory system.system.

Processor used for this: Audience voice Processor used for this: Audience voice processorprocessor

Uses to two microphones to capture the Uses to two microphones to capture the information about the position of different information about the position of different sound sources.sound sources.

So that phone can lock the desired voice So that phone can lock the desired voice and remove all others. and remove all others.

FCT vs FFTFCT vs FFT

1.1. FFT transforms the audio signal into the FFT transforms the audio signal into the frequency domain on a linear scale, while the frequency domain on a linear scale, while the FCT performs its transformation on a FCT performs its transformation on a logarithmic frequency scalelogarithmic frequency scale..

2.2. The FCT provides greater accuracy in The FCT provides greater accuracy in representing the audio signal at both low and representing the audio signal at both low and high frequencieshigh frequencies. .

3.3. The FFT transforms the audio signal by reading The FFT transforms the audio signal by reading blocks or frames of data that are taken at a blocks or frames of data that are taken at a particular frame rate. The FCT continuously particular frame rate. The FCT continuously streams the incoming signal into the streams the incoming signal into the transformation. transformation.

TECHNOLOGYTECHNOLOGY

Processes in voice processorProcesses in voice processor

1.1. Fast Cochlea TransformFast Cochlea Transform

2.2. CharacterizationCharacterization

3.3. GroupingGrouping

4.4. SelectingSelecting

5.5. Inverse Fast Cochlea TransformInverse Fast Cochlea Transform

FAST COCHLEA TRANSFORMFAST COCHLEA TRANSFORM

Convert sounds into a three Convert sounds into a three dimensional, high-quality spectral dimensional, high-quality spectral representation of the sound mixturerepresentation of the sound mixture

Frequency transformation Frequency transformation

Frequency transformationFrequency transformation

CHARACTERIZATIONCHARACTERIZATION

hints for the different sound components hints for the different sound components are computed which include:are computed which include:

1.1. Pitch:Pitch: a male voice and a female voice a male voice and a female voice can be easily separated using Pitchcan be easily separated using Pitch

2.2. Spatial location:Spatial location: to locate the direction to locate the direction from which a sound is coming and its from which a sound is coming and its distance to each of the microphonesdistance to each of the microphones. .

3.3. Onset time:Onset time: Frequency components Frequency components from a single sound source often start from a single sound source often start and/or stop at the same time. and/or stop at the same time.

GROUPING & SELECTINGGROUPING & SELECTING

A grouping is process of clustering operation in A grouping is process of clustering operation in which signals with similar attributes are grouped which signals with similar attributes are grouped into one auditory stream and signals with into one auditory stream and signals with dissimilar attributes are grouped into another dissimilar attributes are grouped into another auditory stream.auditory stream.

The Selector process allows the separated The Selector process allows the separated auditory sound sources to be prioritized and auditory sound sources to be prioritized and

selected as appropriate for the given applicationselected as appropriate for the given application. .

INVERSE FAST COCHLEA INVERSE FAST COCHLEA TRANSFORM TRANSFORM

The Inverse Fast Cochlea Transform process The Inverse Fast Cochlea Transform process converts the Fast Cochlea Transform data back converts the Fast Cochlea Transform data back into reconstructed, cleaned-up, high-quality into reconstructed, cleaned-up, high-quality digital audio which is then converted back to an digital audio which is then converted back to an analog signal, and made available for analog signal, and made available for transmission.transmission.

ADVANTAGESADVANTAGES

1.1. Instantaneous noise suppression.Instantaneous noise suppression.

2.2. Advanced acoustic echo cancellation.Advanced acoustic echo cancellation.

3.3. Ease of integration.Ease of integration.

4.4. Low power consumption.Low power consumption.

5.5. Extensible architecture.Extensible architecture.

CONCLUSIONCONCLUSION

Thus the introduction of Audience Thus the introduction of Audience voice processor will be a revolution in voice processor will be a revolution in the field of mobile.the field of mobile.

Thus we can have a clear and noise Thus we can have a clear and noise free callsfree calls

REFERENCESREFERENCES

1.1. http://ieeexplore.ieee.org/Xplore/login.jsp?url=http://http://ieeexplore.ieee.org/Xplore/login.jsp?url=http://ieeexplore.ieee.org/iel5/2/45971 19/04597148.pdfieeexplore.ieee.org/iel5/2/45971 19/04597148.pdf%3Farnumber%3D4597148&authDecision%3Farnumber%3D4597148&authDecision=-203=-203

2.2. http://www.audience.com/product_technology.htmlhttp://www.audience.com/product_technology.html