Sound input apparatus

• US 5,675,655 A
• Filed: 04/10/1995
• Issued: 10/07/1997
• Est. Priority Date: 04/28/1994
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Hatae, Shinichi
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): Mei, Xu
• Application Number:
  US08/419,378
• Time in Patent Office: 911 Days
• Field of Search: 381/26, 381/92, 381/94, 381/95, 381/97, 381/98, 381/122, 381/111, 381/93, 381/168, 381/169, 381/81, 367/126
• US Class Current: 381/26
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04S 2400/15 Aspects of sound capture and related signal processing for recording or reproduction

Abstract

A sound input apparatus according to the present invention subtracts, from the output signal from a first microphone, the output signal of a second microphone which is arranged in a manner different from that of the first microphone to output the subtracted signal and controls the level of the signal of the second microphone in response to the level of the subtracted signal. The sound input apparatus simply constructed in this way achieves a narrowed sound directivity when picking up sound and presents high-quality audio signal while keeping the influence of ambient noise to a minimum.

Claims

1. A sound input apparatus for providing stereophonic sound output comprising:

(a) first sound pick-up means for converting sound into an electrical signal;

(b) second sound pick-up means, disposed to have its maximum directivity to be oriented in a direction different from a direction of maximum directivity of said first sound pick-up means, for converting sound into an electrical signal;

(c) subtraction means for outputting a signal obtained by subtracting an output of said second sound pick-up means from an output of said first sound pick-up means;

(d) level control means for controlling the level of the signal outputted from said second sound pick-up means in accordance with the level of the signal outputted from said subtraction means; and

(e) circuit means receiving said signals outputted from said subtraction means and said signal outputted from said second sound pickup means for providing first and second stereophonic output signals.

2. A sound input apparatus according to claim 1, wherein said first sound pick-up means includes a first microphone disposed to allow its maximum directivity to be oriented in a desired direction.

3. A sound input apparatus according to claim 2, wherein said second sound pick-up means includes a second microphone disposed to allow its maximum directivity to be oriented in a direction different from the direction of the maximum directivity of the first microphone.

4. A sound input apparatus according to claim 2, wherein said second sound pick-up means includes:

(a) a pair of second microphones disposed to allow their maximum directivities to be oriented in directions different from the direction of the maximum directivity of the first microphone; and

(b) addition means for outputting a signal obtained by adding outputs of the second microphones.

5. A sound input apparatus according to claim 4, wherein said level control means includes amplifying means for amplifying the signal outputted from said addition means according to an amplification factor corresponding to the level of the signal outputted from said subtraction means and for supplying the amplified signal to said subtraction means.

6. A sound input apparatus comprising:

(a) a first microphone disposed to allow its maximum directivity to be oriented in a desired direction;

(b) first coefficient multiplying means for multiplying a signal outputted from said first microphone by an arbitrary coefficient to output a resultant signal;

(c) a pair of second microphones disposed to allow their maximum directivities to be oriented in directions different from the direction of the maximum directivity of said first microphone;

(d) arithmetic processing means for performing adding or subtracting operation between outputs of said second microphones to output a resultant signal;

(e) second coefficient multiplying means for multiplying the signal outputted from said arithmetic processing means by an arbitrary coefficient to output a resultant signal;

(f) subtraction means for outputting, as a first channel signal, a signal obtained by subtracting the signal outputted from said second coefficient multiplying means from the signal outputted from said first coefficient multiplying means;

(g) addition means for outputting, as a second channel signal, a signal obtained by adding the signal outputted from said second coefficient multiplying means and the signal outputted from said first coefficient multiplying means; and

(h) setting means provided with a first sound pick-up mode in which sound is picked up in a first directivity and a second sound pick-up mode in which sound is picked up in a second directivity which is narrower than the first directivity, for performing the setting corresponding to either of the two sound pick-up modes, wherein said setting means, in the first sound pick-up mode, sets said arithmetic processing means to output a signal obtained by performing subtracting operation between the outputs of said second microphones, and said setting means, in the second sound pick-up mode, sets said arithmetic processing means to output a signal obtained by performing adding operation between the outputs of said second microphones, allows said subtraction means to output, as a first channel signal and a second channel signal, a signal obtained by subtracting the signal outputted from said second coefficient multiplying means from the signal outputted from said first coefficient multiplying means, and allows said second coefficient multiplying means to output a signal obtained by multiplying the signal outputted from said arithmetic processing means by a coefficient corresponding to the level of the signal outputted from said subtraction means.

7. A sound input apparatus according to claim 6, being arranged so that the directivity of the apparatus varies in the first sound pick-up mode by varying the coefficients with which said first and second coefficient multiplying means perform multiplication.

8. A sound input apparatus according to claim 6, wherein said first channel signal is a right audio signal and said second channel signal is a left audio signal.

9. A sound input apparatus comprising:

(a) a first microphone disposed to allow its maximum directivity to be oriented in a desired direction;

(b) first coefficient multiplying means for multiplying a signal outputted from said first microphone by an arbitrary coefficient to output a resultant signal;

(c) a pair of second microphones disposed to allow their maximum directivities to be oriented in directions different from the direction of the maximum directivity of said first microphone;

(d) arithmetic processing means for performing adding or subtracting operation between outputs of said second microphones to output a resultant signal;

(e) second coefficient multiplying means for multiplying the signal outputted from said arithmetic processing means by an arbitrary coefficient to output a resultant signal;

(f) filter means for filtering the signal outputted from said second coefficient multiplying means to output a resultant signal;

(g) subtraction means for outputting, as a first channel signal, a signal obtained by subtracting the signal outputted from said filter means from the signal outputted from said coefficient multiplying means;

(h) addition means for outputting, as a second channel signal, a signal obtained by adding the signal outputted from said filter means and the signal outputted from said first coefficient multiplying means; and

(i) setting means provided with a first sound pick-up mode in which sound is picked up in a first directivity and a second sound pick-up mode in which sound is picked up in a second directivity which is narrower than the first directivity, for performing the setting corresponding to either of the two sound pick-up modes, wherein said setting means, in the first sound pick-up mode, sets said arithmetic processing means to output a signal obtained by performing subtracting operation between the outputs of said second microphones, and said setting means, in the second sound pick-up mode, sets said arithmetic processing means to output a signal obtained by performing adding operation between the outputs of said second microphones, allows said subtraction means to output, as a first channel signal and a second channel signal, a signal obtained by subtracting the signal outputted from said filter means from the signal outputted from said first coefficient multiplying means, and allows said filter means to output a signal obtained by filtering the signal outputted from said second coefficient multiplying means according to a filter characteristic corresponding to the level of the signal outputted from said subtraction means.

10. A sound input apparatus according to claim 9, being arranged so that the directivity of the apparatus varies in the first sound pick-up mode by varying the coefficients with which said first and second coefficient multiplying means perform multiplication.

11. A sound input apparatus according to claim 9, wherein said first channel signal is a right audio signal and said second channel signal is a left audio signal.

12. A sound input apparatus having respective wide and narrow directional modes of operation comprising:

(a) first sound pick-up means for converting sound into an electrical signal;

(b) a pair of second sound pick-up means, disposed to have their maximum directivities to be oriented in directions different from a direction of maximum directivity of said first sound pick-up means, for converting sound into electrical signals; and

(c) switching means for additively combining electrical signals generated by said pair of second sound pick-up means in said narrow directional mode of said apparatus and for subtractively combining electrical signals generated by said pair of second sound pick-up means in said wide directional mode of said apparatus.

13. A sound input apparatus according to claim 12, further including subtraction means for inputting both a signal obtained from said switching means in each of said narrow and wide directional modes and a signal generated by said first sound pick-up means.

14. A sound input apparatus according to claim 12, further including addition means operative exclusively in said wide directional mode of said apparatus for inputting both a signal obtained from said switching means in said wide directional mode and a signal generated by said first sound pick-up means.

15. A sound input apparatus according to claim 13, further including addition means operative exclusively in said wide directional mode of said apparatus for inputting both a signal obtained from said switching means in said wide directional mode and a signal generated by said first sound pick-up means.