Receiving circuit

• US 5,692,017 A
• Filed: 07/20/1995
• Issued: 11/25/1997
• Est. Priority Date: 07/20/1994
• Status: Expired due to Fees

• Current Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Original Assignee: NEC Corporation
• Inventors: Shiokawa, Toshimichi
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US08/504,513
• Time in Patent Office: 859 Days
• Field of Search: 375/244, 375/254, 375/346, 375/348, 381/56, 381/94, 395/2.23, 395/2.24, 395/2.35, 395/2.37, 395/2.42, 455/67.3, 327/72-73
• US Class Current: 375/346
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• CPC Class Codes: G10L 25/93 Discriminating between voiced and unvoiced parts of speech signals G10L25/90 takes precedence

Abstract

A receiving circuit has an automatic level setting function for a background noise on the receiver side to generate a background noise free from incongruous aural sensation. This circuit is equipped with a voice/silence unit which detects whether a received signal is in a voice or a voiceless state, a signal level detection unit which detects the signal level of the received signal, a background noise unit which outputs a background noise, a selector which selects and outputs the received signal during the voiced period and the output signal of the background noise unit during the voiceless period, a level holding unit which holds the signal level output at the preceding sampling timing detected by the signal level detection unit, and a comparison unit which compares the present signal level output of the signal level detection unit and the preceding signal level output held in the holding unit, the background noise signal being thus obtained, by adding or subtracting a predetermined specified noise level to or from, or by giving any change to, the preceding background noise signal.

Claims

1. A receiving circuit comprising voice/silence detection means for detecting whether an input signal is voiced or voiceless, signal level detection means for detecting a signal level of said input signal, background noise outputting means for outputting a background noise signal, selection means for selecting and outputting said input signal during a voiced period and said background noise signal during a voiceless period, holding means for temporarily holding an output signal from said signal level detection means, and comparison means for comparing an output signal currently produced by said signal level detection means with an output signal from said holding means, said background noise outputting means outputting said background noise signal in response to an output of said comparison means.

2. The receiving circuit as claimed in claim 1, wherein said background noise outputting means controls, in response to the output of said comparison means, said background noise signal such that a change in said background noise signal from a previous level to a current level is suppressed below a predetermined level.

3. The receiving circuit as claimed in claim 1, wherein said background noise outputting means outputs said background noise signal such that said background noise signal has no change the output of said comparison means is in a first state, has a positive change when the output of said comparison means is in a second state, and has a negative change when the output of said comparison means is in a third state.

4. The receiving circuit as claimed in claim 1, wherein said holding means holds the output signal from said signal level detection means at timing when said voice/silence detection means represents a transition in said input signal from a voiced state to a voiceless state.