Speech circuit controlling sidetone signal by background noise level

• US 5,640,450 A
• Filed: 06/21/1995
• Issued: 06/17/1997
• Est. Priority Date: 07/08/1994
• Status: Expired due to Fees

• Current Assignee: Kokusai Electric Co., Ltd.
• Original Assignee: Kokusai Electric Co., Ltd.
• Inventors: Watanabe, Osamu
• Primary Examiner(s): Zele, Krista M.
• Assistant Examiner(s): Kumar, Devendra
• Application Number:
  US08/492,753
• Time in Patent Office: 727 Days
• Field of Search: 379/388, 379/389, 379/390, 379/391, 379/392, 379/409, 379/420, 381/57, 381/94, 381/104, 381/107, 381/108
• US Class Current: 379/392
• CPC Class Codes: H04M 1/585 implemented without inductive element
• CPC Class Codes: H04M 9/08 Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic

Abstract

A speech circuit is disclosed which solves the serious problem of the degradation of the articulation of received speech voice in conventional circuits and permits pleasant communications at places where the background noise level is high. The circuit has a construction in which an input signal from a microphone is attenuated in correspondence to the background noise level to form a sidetone signal and a received speech signal from a speech channel is amplified in correspondence to the background noise level to form a new received speech signal.

Claims

1. A speech circuit, in which a received speech signal is added by an adder with a sidetone signal produced by attenuating a speech signal of a talker from a first microphone of said speech circuit so that a speech output from said talker is heard at the output from a speaker therein,

said speech circuit comprising:

an auxiliary microphone other than said first microphone for picking up background noise;

a level detector for receiving background noise from said auxiliary microphone and detecting the background noise level;

an attenuator controller for outputting an attenuation control signal effective to decrease or increase the amount of attenuation in dependence upon whether said background noise level from said level detector is high or low; and

a variable attenuator for receiving said speech signal from said first microphone and attenuating only said speech signal in accordance with said attenuation control signal to produce said sidetone signal.

2. A speech circuit, in which a received speech signal is added by an adder with a sidetone signal produced by attenuating a speech signal of a talker from a first microphone therein so that a speech output from said talker is heard at the output from a speaker,

said speech circuit comprising:

an auxiliary microphone other than said first microphone for picking up background noise;

a level detector for receiving background noise from said auxiliary microphone and detecting the background noise level;

an attenuation controller for outputting an attenuation control signal effective to decrease or increase the amount of attenuation, depending upon whether said background noise level provided form said level detector is low or high;

a variable attenuator for receiving said speech signal from said first microphone and attenuating only said speech signal in accordance with said attenuation control signal to produce said sidetone signal;

an amplification controller for outputting an amplification control signal which causes a decrease or increase in the amount of amplification of said received speech signal, depending upon whether said background noise level provided from said level detector is low or high; and

a variable amplifier for receiving said received speech signal and for amplifying said received speech signal in accordance with said amplification control signal.

3. A speech circuit according to claim 2, in which said auxiliary microphone is oriented in a direction of the minimum sensitivity to vocal sounds heard from said talker.