Method of and an apparatus for eliminating background noise in digital sound recording

• US 5,546,497 A
• Filed: 05/02/1994
• Issued: 08/13/1996
• Est. Priority Date: 05/02/1994
• Status: Expired due to Term

• Current Assignee: United Microelectronics Corporation
• Original Assignee: United Microelectronics Corporation
• Inventors: Kao, Oliver C. K.
• Primary Examiner(s): Tung, Kee M.
• Application Number:
  US08/236,925
• Time in Patent Office: 834 Days
• Field of Search: 395/2.35, 395/2.36, 395/2.37, 395/2, 381/46, 381/47, 381/51, 360/32, 360/36.2
• US Class Current: 704/226
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: G11B 20/24 for reducing noise control of amplification in general, e.g. dependent upon noise level H03G

Abstract

A method of suppressing background noise in a digital sound recording and reproducing system includes the steps of preselecting a specific voltage range to be considered to contain substantially all background noise, selecting a quiet sound benchmark voltage taken as zero output, defining a number of least significant bits of a digital sound signal confining the noise, defining voltages corresponding to the number of least significant bits, and replacing these voltages within the voltage range for both positive and negative most significant bits around the benchmark voltage with the benchmark voltage which clears sound signals from this type of noise. An apparatus for practicing the method employs logic circuitry providing suppression of signals within the preselected range.

Claims

1. A method of eliminating background noise in a digital sound recording and reproducing system comprising the steps of:

converting analog sound signals to digital sound signals in a speech processing unit and storing said digital sound signals in a memory means,

selecting a voltage amplitude range containing substantially all background noise digital sound signals,

changing said digital sound signals of said noise to digital signals that represent essentially a zero sound output within said voltage amplitude range in the course of reproducing, and

converting said digital signals into an analog form, to thereby reproduce sound signals without said background noise,

said changing said digital sound signals of said noise is made through selecting a quiet sound benchmark voltage, defining a number of least significant bits of said digital sound signal confining said noise, defining voltages corresponding to said number of least significant bits, and replacing said voltages within said voltage range for both positive and negative most significant bits around said benchmark voltage with said benchmark voltage.

2. The method according to claim 1, wherein said voltage amplitude range is selected between 2.236 volts and 2.664 volts.

3. The method according to claim 1, wherein said voltage amplitude range is selected between 2.266 volts and 2.687 volts.

4. An apparatus for suppressing background noise in a digital sound recording and reproducing system comprising sound processing means to convert analog sound signals into digital sound signals, means connected with said processing means for eliminating signals within a preselected voltage range characteristic for background noise, and digital-to-analog converting means controlled by said eliminating means for reproducing analog sound signals, said eliminating means includes first logic means, said first logic means being controlled by most significant bits of said digital sound signals, a number and values of said most significant bits defining said preselected voltage range;

and second logic means controlled by said first logic means to zero outputs of said second logic means when a number and values of said most significant bits lie within the limits defining said preselected voltage range.

5. The apparatus according to claim 4, wherein said preselected voltage range lies between 2.236 volts and 2.664 volts.

6. The apparatus according to claim 4, wherein said preselected voltage range lies between 2.266 volts and 2.687 volts.