Listening device

• US 20060222192A1
• Filed: 03/15/2006
• Published: 10/05/2006
• Est. Priority Date: 03/17/2005
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: EMMA Mixed Signal CV
• Inventors: Matthey, Marc
• Granted Patent: US 7,957,543 B2
• Time in Patent Office: Days
• US Class Current: 381/312
• CPC Class Codes: G10L 2021/02085 Periodic noise
• CPC Class Codes: G10L 21/02 Speech enhancement, e.g. noise reduction or echo cancellation reducing echo effects in line transmission systems H04B3/20; echo suppression in hands-free telephones H04M9/08
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H04R 2225/43 Signal processing in hearing aids to enhance the speech intelligibility
• CPC Class Codes: H04R 2225/57 Aspects of electrical interconnection between hearing aid parts
• CPC Class Codes: H04R 25/00 Deaf-aid sets , i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception electrical stimulation of auditory nerves to promote the auditory function A61N1/36038; optical stimulation of auditory nerves to promote the auditory function A61N5/0622
• CPC Class Codes: H04R 25/43 Electronic input selection or mixing based on input signal analysis, e.g. mixing or selection between microphone and telecoil or between microphones with different directivity characteristics H04R25/407 takes precedence
• CPC Class Codes: H04R 25/505 using digital signal processing
• CPC Class Codes: H04R 25/602 of batteries

Abstract

In a listening device such as for example a hearing aid (1) where an input signal (10) is received by a microphone (2), converted from analog to digital (3), digitally processed (4) including a conversion from a time domain into a frequency domain, converted from digital to analog (5) and transmitted to a user by means of a loudspeaker (6), the internal digital processing (4) generates an unwanted noise signal, the so called undesired periodic noise (12), at specific frequencies. The undesired periodic noise is coupled via ground and the battery (7) into the signal processing path. According to the invention, the undesired periodic noise is filtered out of the input signal (10.2) during the digital signal processing (4), after the conversion of the digital signal into the frequency domain.

Claims

1. Method for processing an analog acoustic signal, particularly for processing an audio signal (10.1) in a listening device (1), including a step of converting the analog acoustic signal into a digital signal (10.2) and a step of processing the digital signal (10.2) including converting it from a time domain into a frequency domain, where a noise signal is generated by processing said digital signal and where said noise signal is superposed (12) on said analog acoustic signal, characterized in that said step of processing the digital signal includes a step of filtering said noise signal out of said digital signal after said conversion of the digital signal into the frequency domain.

2. Method according to claim 1, characterized in that the step of processing the digital signal is made at regular time intervals (T).

3. Method according to claim 2, characterized in that said step of applying a time to frequency transform includes determining a complex transformation value, where said noise signal is filtered out of said complex transformation value by subtracting a first correction value from a real part of said complex transformation value and by subtracting a second correction value from an imaginary part of said complex transformation value.

4. Method according to claim 3, characterized in that said noise signal is filtered out with a highpass digital filter where said first and second correction values are updated after subtracting them from the real and imaginary parts of said complex transformation value respectively.

5. Method according to claim 4, characterized in that a first initial value is set for said first correction value and in that a second initial value is set for said second correction value.

6. Method according to claim 4, characterized in that said first and second correction values are updated only when an energy of said complex transformation value is smaller than a predetermined threshold value.

7. Method according to claim 1, characterized in that said analog acoustic signal (10.1) is converted into said digital signal (10.2) with a given sampling frequency, a frequency range from 0 Hz to half the sampling frequency being divided into a plurality of frequency bands where said step of filtering said noise signal out of said digital signal (10.2) is carried out for at least one of said frequency bands.

10. Method according to any of claim 5, characterised in that said first and second correction values are updated only when an energy of said complex transformation value is smaller than a predetermined threshold value.

11. Method according to any of claim 2, characterized in that said analog acoustic signal (10.1) is converted into said digital signal (10.2) with a given sampling frequency, a frequency range from 0 Hz to half the sampling frequency being divided into a plurality of frequency bands where said step of filtering said noise signal out of said digital signal (10.2) is carried out for at least one of said frequency bands.

12. Method according to any of claim 3, characterized in that said analog acoustic signal (10.1) is converted into said digital signal (10.2) with a given sampling frequency, a frequency range from 0 Hz to half the sampling frequency being divided into a plurality of frequency bands where said step of filtering said noise signal out of said digital signal (10.2) is carried out for at least one of said frequency bands.

13. Method according to any of claim 4, characterized in that said analog acoustic signal (10.1) is converted into said digital signal (10.2) with a given sampling frequency, a frequency range from 0 Hz to half the sampling frequency being divided into a plurality of frequency bands where said step of filtering said noise signal out of said digital signal (10.2) is carried out for at least one of said frequency bands.

14. Method according to any of claim 5, characterized in that said analog acoustic signal (10.1) is converted into said digital signal (10.2) with a given sampling frequency, a frequency range from 0 Hz to half the sampling frequency being divided into a plurality of frequency bands where said step of filtering said noise signal out of said digital signal (10.2) is carried out for at least one of said frequency bands.

15. Method according to any of claim 6, characterized in that said analog acoustic signal (10.1) is converted into said digital signal (10.2) with a given sampling frequency, a frequency range from 0 Hz to half the sampling frequency being divided into a plurality of frequency bands where said step of filtering said noise signal out of said digital signal (10.2) is carried out for at least one of said frequency bands.

8. Listening device (1), particularly hearing aid, including an analog to digital converter (3) for converting an analog acoustic input signal (10.1) into a digital input signal (10.2), a processing device (4) for processing said digital input signal and determining a digital output signal (11.2), including converting the digital input signal from a time domain into a frequency domain, and a digital to analog converter (5) for converting the digital output signal (11.2) into an analog output signal (11.1), the processing device (4) being connected to said analog to digital converter (3) and to said digital to analog converter (5), said processing device (4) being built such that it processes said digital input signal at regular time intervals thereby generating a noise signal (12), where the listening device (1) is built such that said noise signal (12) is superposed on said analog acoustic input signal (10.1), characterized in that said processing device includes filtering means for filtering said noise signal (12) out of said digital input signal (10.2) after said conversion of the digital input signal into the frequency domain.

9. Processing device (4) for processing a digital input signal (10.2) with a superposed noise signal (12) and determining a digital output signal (11.2) for a listening device (1) as claimed in claim 8, where said processing device (4) is built such that it processes said digital input signal (10.2) at regular time intervals thereby generating said noise signal (12), characterized in that said processing device (4) is implemented as an integrated circuit on a programmable microchip and includes filtering means for filtering said noise signal (12) out of said digital input signal (10.2).