New denoising technology helps improve navigation speech recognition

Recently, Japan Electric Co., Ltd. (hereinafter referred to as NEC) has developed a new noise removal technology that can greatly improve the operation accuracy of the navigator voice. When the car is installed with this technology, when the air conditioner is turned on or the window is opened, the navigator can smoothly recognize the voice for navigation despite the wind noise and tire noise.

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The NEC denoising technology uses two microphones to collect sound. Two steps can easily filter out the noise inside and outside the car, and the collected sound can be adjusted to the voice that is easily recognized by the navigator. Even in the environment of 5 times the normal noise, the speech recognition can be realized smoothly.

Since the NEC denoising new technology processes the collected signals (mixed speech and noise) by a signal processing circuit inside the microphone, the denoising system of this technology consists of only two microphones and wires.

The signal processing flow of the noise removal technology is as follows:

●Microphone installation

The car manufacturer can analyze the location of the noise source such as the air conditioner in the car and the way the sound propagates to the inside of the car. By adjusting the two microphones before and after the small pitch, the noise from the front and the voice of the speaker can be distinguished and extracted separately. As a result, the noise processing efficiency is improved.

●Two-step easy to filter car noise

The first step uses the similarity of the noise waveforms collected by the two microphones to accurately capture the waveform of the noise over time, extract the main noise components, and eliminate noise by signal processing. The second step is to use the similarity between the speeches to eliminate the noise that is not cleaned in the first step. By processing the signals (mixed speech and noise) detected by the two microphones in the above two steps, the noise component can be greatly reduced.

● Strengthen the restored voice

Automatically selected according to two speech models developed by NEC to adjust the speech that is difficult to be recognized by the navigator due to distortion during denoising. The specific operation is that the NEC will form a model of the components and changes of the real speech, compare the distorted speech with the model speech, and automatically enhance and restore the distorted speech to form a waveform signal that can be recognized by navigation.

●Full prospect of noise filtering technology

For mobile phone manufacturers, the addition of mobile phone GPS functions has become a trend, and it is also to achieve better noise filtering effect, but no more than cars, mobile phones have higher requirements on size and power consumption, mobile phones can not be like cars Manufacturers like to install two microphones in the car, low-noise amplifier (LNA) and GPS receiver / processor combined with integrated circuits as a solution, which has been greatly developed in the mobile phone industry. The LNA has high noise sensitivity and can be used in driving navigation.

But the LNA integrated system doesn't always filter out all the noise, especially in areas with high noise levels like city streets. In order to reduce front-end noise during driving and improve noise sensitivity, designers are considering the design of external LNAs. The external LNA can be mounted near the vehicle antenna.

The in-vehicle LNA, combined with tuning and distributed filtering, can filter out more than 1.5 decibels of noise more efficiently. The off-board LNA, combined with the distributed filtering method, enhances the anti-jamming capability of navigation for external signals.

Summary: NEC expects that noise-reduction technology will be put into production this year. The sales target is directly targeted at auto manufacturers, and consumers are indirectly benefiting. In theory, this technology can be installed on any price model. Just do not know if NEC will come to a high-end marketing?

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