JPH11243597A - Microphone switching system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable optimum recording corresponding to the environment and the purpose of recording and to remove unwanted signal components such as dark noises. SOLUTION: A microphone amplifier 3, first band-pass filter 4 and first impedance converting circuit 5 are connected serially to a directional microphone 1, and a second band pass filter 7 and a second impedance converting circuit 8 are serially connected to a non-directional microphone 2. When a changeover switch 6 is switched and connected to the output terminal of the first impedance converting circuit 5, the directional microphone 1 functions as a voice pickup system which is suitable for recording only voices in the specified direction. When the changeover switch 6 is switched and connected to the second impedance converting circuit 8 or attenuation level setting means 9, the non-directional microphone 2 functions as a voice pickup system which is suitable for conference recording or voice memo recording.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone switching system suitable for picking up and recording sound using directional and omnidirectional microphones.
More specifically, the present invention relates to a microphone switching system in which a directional microphone and an omnidirectional microphone can be switched according to a use situation, and a signal gain of the microphone can be switched according to a recording purpose.

[0002]

2. Description of the Related Art Conventionally, a directional (unidirectional) or omnidirectional (omnidirectional) microphone is used in a microphone switching system in a voice recording device such as a tape recorder, and the microphone is picked up by the microphone. An audio signal is output to a recording head through a preamplifier and a power amplifier, and the recording head records the audio signal on a recording medium.

[0003]

In the above-mentioned conventional microphone switching system, when a unidirectional microphone is used as the microphone, only a sound in a specific direction is picked up and recorded as in a performance or the like. Sometimes preferred, but not suitable for picking up audio from each direction, such as when recording audio during a meeting. Also, when an omnidirectional microphone is used, it is suitable for picking up sound from each direction, contrary to the above case, but it is not suitable for picking up sound only in a specific direction effectively. There's a problem. Further, in a conventional microphone switching system using a non-directional and unidirectional microphone, signal components other than human noise and dark noise due to a magnetic field of a battery included in a signal picked up by these microphones. In addition to these, there is a problem that these signal components are also recorded because they cannot be cut, and the recording environment is limited depending on the directional characteristics of the microphone used because the gain of the signal from the microphone is constant. was there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and enables an optimum recording according to a recording environment and a recording purpose, and also removes unnecessary signal components such as background noise. It is an object of the present invention to provide a microphone switching system that can be used.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for picking up sound using directional and omni-directional microphones by switching these microphones to audio amplification means. A microphone switching system that enables accurate recording by connecting to an output end of the directional microphone, and a first band-pass filter that limits a pass band of a frequency of an audio signal picked up by the directional microphone; A second band-pass filter connected to an output terminal of the omni-directional microphone for limiting a pass band of a frequency of an audio signal picked up by the omni-directional microphone, and an output signal passing through the second band-pass filter Attenuation level setting means for setting a plurality of attenuation levels in accordance with a recording purpose; A switching means for switching and connecting an input terminal of the audio amplification means to a contact provided at an output terminal of the pass filter and a contact provided for each attenuation level of the attenuation level setting means; and an output terminal of the first band-pass filter. A first impedance conversion circuit that is connected between the contacts provided at the output terminal and that lowers the impedance of a circuit system reaching the input terminal of the audio amplification means through the switching means to reduce the influence on noise; The impedance of a circuit system connected between the output terminal of the pass filter and the input terminal of the attenuation level setting means and reaching the input terminal of the audio amplification means through the attenuation level setting means and the switching means is reduced to reduce the influence on noise. And a second impedance conversion circuit.

According to the present invention, when the switching means is switched and connected to the output terminal of the first impedance conversion circuit, the directional microphone functions as a sound pickup system suitable for recording only sound in a specific direction. . Also,
When the switching means is switched and connected to a terminal provided for each attenuation level of the attenuation level setting means, the omnidirectional microphone functions as an audio pickup system suitable for recording a conference or recording a voice memo. Therefore, unnecessary signal components such as background noise can be removed, and the directional microphone and the omnidirectional microphone can be used in a specification according to a recording environment and a recording purpose such as a performance, a conference, and a voice memo, And optimal recording becomes possible.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a microphone switching system according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an overall configuration in which a microphone switching system of the present invention is applied to a recording / reproducing device such as a tape recorder, FIG. 2 is a circuit diagram showing a configuration of a microphone switching system in an embodiment of the present invention, and FIG. FIG. 4 is a frequency characteristic diagram of the microphone at the time of a performance, a conference, and recording of a voice memo according to the embodiment of the present invention.

In FIG. 1, 1 is directivity (unidirectional).
And 2 are omnidirectional (omnidirectional) microphones. At the output end of the directional microphone 1, a microphone amplifier (amplifier) 3 for amplifying the audio signal picked up by the directional microphone 1, a pass band of the frequency of the audio signal amplified by the microphone amplifier 3, for example, 340 Hz A first band-pass filter 4 for limiting the frequency to a range of up to 3.4 kHz; A first impedance conversion circuit 5 that lowers the impedance to reduce the influence on noise is connected vertically, and further,
The output terminal of the first impedance conversion circuit 5 is connected to a fixed contact 6A of a changeover switch 6 constituting a changeover means. The movable contact 6D of the changeover switch 6 is connected to the input terminal of the preamplifier 10.

The output end of the omnidirectional microphone 2 has a passband of the frequency of the audio signal picked up by the omnidirectional microphone 2, for example, 72 Hz to
The impedance of the second band-pass filter 7, which is limited to the range of 7 kHz, and the circuit system (path including wiring and contacts) from the output terminal of the second band-pass filter 7 to the input terminal of the preamplifier 10 are reduced to reduce the influence on noise. A second impedance conversion circuit 8 is connected in cascade, and an output terminal of the second impedance conversion circuit 8 receives an output signal from the second band-pass filter 7 through the second impedance conversion circuit 8 for conference and voice memo recording. Attenuation level setting means 9 for setting a plurality of attenuation levels in accordance with a recording purpose, such as a recording purpose, is connected. The attenuation level setting means 9 includes a plurality of resistors R1, R2 connected in series between the output terminal of the second impedance conversion circuit 8 and the ground. The fixed contacts 6B and 6C of the changeover switch 6 are connected to a connection point (terminal) between the output terminal of the second impedance conversion circuit 8 and the resistors R1 and R2, respectively.

Between the output terminal of the preamplifier 10 and the input terminal of the power amplifier 12, first and second switches 18A and 18B for switching between reproduction and recording are interposed.
The fixed reproduction contacts a, of the changeover switches 18A, 18B,
A variable resistor 11 for adjusting the gain at the time of reproduction is connected between the terminals a. The fixed contacts b for recording of the changeover switches 18A and 18B are directly connected to keep the gain constant. Further, a speaker 13 and an earphone jack 14 are connected to an output end of the power amplifier 12, and a magnetic head 15 for recording and reproduction is connected. The preamplifier 10 and the power amplifier 12
Are connected to a control circuit 16 for switching these amplifiers for recording and reproduction. The control circuit 16 is connected to a recording / reproduction switch 17. The changeover switch 17 is switched in conjunction with the changeover switches 18A and 18B. The preamplifier 10 also functions as a preamplifier for amplifying a signal reproduced from a recording medium by the magnetic head 15.

In FIG. 2, a microphone amplifier 3 amplifies an audio signal picked up by a directional microphone 1.
Is an NPN transistor Q1 and this transistor Q1
R11 connected to the base, collector and emitter of the
To R14 and capacitors C11 to C13. Further, the first band-pass filter 4 includes the microphone amplifier 3
And capacitors C14 to C16 and resistors R15 and R16 connected in a π type between the input terminals of the first impedance conversion circuit 5 and
It is composed of The first impedance conversion circuit 5
It is composed of a common collector circuit (emitter follower with high input impedance and low output impedance), and includes an NPN transistor Q2 and this transistor Q2
And resistors C17 and R17 connected to the base and the emitter of the capacitor C17.

In FIG. 2, a second band-pass filter 7 for band-passing the frequency of the audio signal picked up by the omnidirectional microphone 2 includes an output terminal of the omnidirectional microphone 2 and a second impedance conversion circuit 8. It is composed of capacitors C18 to C20 and resistors R19 and R20 connected between the input terminals in a π-type. The second impedance conversion circuit 8 is composed of a common-collector circuit (emitter follower having high input impedance and low output impedance), and includes an NPN transistor Q3 and a resistor R connected to the base and emitter of the transistor Q3.
21, R1, R2 and a capacitor C21. Each circuit having the above configuration is mounted on a wiring board.

The output terminal 5A of the first impedance conversion circuit 5 is connected to a fixed contact 6A of the changeover switch 6 via a DC cut capacitor C31. The output terminal 8A of the second impedance conversion circuit 8 is connected to the changeover switch 6 via a DC cut capacitor C32.
Are connected to the fixed contact 6B. Further, a connection point 8B between the resistors R1 and R2 connected to the output terminal of the second impedance conversion circuit 8 is connected to a fixed contact 6C of the changeover switch 6 via a DC cut capacitor C33.
The movable contact 6D of the changeover switch 6 is connected to the preamplifier 10
Is connected to the input terminal of

Next, the operation of the present embodiment configured as described above will be described. When the microphone switching system is used to record sound from a specific direction such as a performance or a lecture (performance mode), the changeover switch 6 is used.
Is switched to the fixed contact 6A. In this state, the directional microphone 1 is directed to a person who performs or lectures, and voice from the person is picked up by the directional microphone 1. After the audio signal picked up by the directional microphone 1 is amplified by the microphone amplifier 3, the frequency of the pass band is changed by the first band pass filter 4 to, for example, 340 Hz to 3.4 kHz.
Restrict to the range of z and cut off frequencies other than voice such as background noise. The audio signal that has passed through the first band-pass filter 4 is output to the preamplifier 10 through the first impedance conversion circuit 5 and the switch 6. In the first impedance conversion circuit 5, the first bandpass filter 4
The impedance of the circuit system including the wiring from the output terminal of the switch 6 to the input terminal of the preamplifier 10 through the movable contact 6D of the changeover switch 6 and the fixed contact 6A is lowered. As a result, the influence of noise that enters from the wiring of the circuit system, for example, the noise generated by the magnetic field of the built-in battery is reduced. At this time, the frequency characteristic of the microphone including the circuit elements from the output terminal of the first band-pass filter 4 to the input terminal of the preamplifier 10 at the point P in FIG. 1 is as shown by a characteristic curve 41 in FIG.

Here, a recording / reproducing changeover switch 17 is provided.
Is turned on, for example, the changeover switches 18A and 18B associated therewith are switched to the recording fixed contacts b and b, so that the preamplifier 10 is set for recording and the power amplifier 12 functions as a recording driver. Thus, after the audio signal picked up by the directional microphone 1 is amplified by the preamplifier 10, the magnetic head 15 is driven by the power amplifier 12 as a recording driver, and the audio is recorded on a recording medium (not shown). To reproduce the content recorded on the recording medium, the recording / reproduction switch 17 is turned off, and the changeover switches 18A and 18B associated therewith are switched to the fixed reproduction contacts a and a. Thereby, the preamplifier 10 and the power amplifier 1
2 is set for reproduction, and the recording signal read by the magnetic head 15 is amplified by the preamplifier 10 and the power amplifier 12 and output to the speaker 13 so that the contents of the performance or lecture can be reproduced as sound. Become.

By connecting the microphone amplifier 3 to the output system of the directional microphone 1 as described above, the gain of the directional microphone 1 can be increased, so that the sensitivity of the directional microphone 1 is increased and the distance from the sound source is slightly increased. Can be dealt with, and sound in a specific direction at a distance can be reliably recorded. The directional microphone 1
By providing the band-pass filter 4 in the output system, the signal components unnecessary for recording such as dark noise can be reliably cut off. In addition, by providing the impedance conversion circuit (emitter follower), the output system of the directional microphone 1 can be provided. Noise that intrudes into a circuit system including a connected line can be reduced.

In the case of recording a voice from each direction when a conference is held around a round table or a desk (conference mode),
The movable contact 6D of the changeover switch 6 is connected to the fixed contact 6B by switching. In such a state, the sound generated from around the omnidirectional microphone 2 is not omnidirectional.
The frequency of the pass band of the picked-up audio signal is limited by the second band-pass filter 7 to, for example, a range of 72 Hz to 7 kHz, and cuts frequencies other than voice such as background noise. And the second
The audio signal that has passed through the band-pass filter 7 is output to the preamplifier 10 through the second impedance conversion circuit 8 and the switch 6. In the second impedance conversion circuit 8, the movable contact 6D of the changeover switch 6 is passed from the output terminal of the second bandpass filter 7 to the preamplifier 1 through the fixed contact 6B.
The impedance of the circuit system including the wiring leading to the 0 input terminal is lowered. As a result, the influence of noise that enters from the wiring of the circuit system, for example, the noise generated by the magnetic field of the built-in battery is reduced. The audio signal picked up by the omnidirectional microphone 2 is amplified by the preamplifier 10, and then the magnetic head 15 is driven by the power amplifier 12 functioning as a recording driver, and the audio is recorded on a recording medium (not shown). At this time, the frequency characteristic of the microphone including the circuit element from the output terminal of the second bandpass filter 7 to the input terminal of the preamplifier 10 at the point P in FIG. 1 is as shown by a characteristic curve 42 in FIG.

By providing the second band-pass filter 7 in the output system of the omnidirectional microphone 2 as described above, signal components unnecessary for recording such as dark noise can be reliably cut, and an impedance conversion circuit (emitter follower) Is provided, it is possible to reduce noise entering a circuit system including a line connected to the output system of the omnidirectional microphone 2. Thus, the omnidirectional microphone 2 can be used to reliably record a conference in a place surrounding a round table or a desk.

When the microphone switching system functions as a voice memo (voice memo mode),
The movable contact 6D of the changeover switch 6 is switched and connected to the fixed contact 6C. Accordingly, the output signal level of the second impedance conversion circuit 8 is attenuated by the amount divided by the resistors R1 and R2 of the attenuation level setting means 9 as compared with the case of the conference recording. At this time, the output level without attenuation is set to 0.
If it is dB, the sensitivity is reduced by 8 dB. In such a state, the sensitivity of the omnidirectional microphone 2 is reduced overall, so that the omnidirectional microphone 2 is brought close to the mouth to generate sound. Thus, the sound is picked up by the omnidirectional microphone 2, and the frequency of the pass band of the picked-up sound signal is limited by the second band-pass filter 7 to, for example, a range of 72 Hz to 7 kHz. Cut frequencies other than. Then, the audio signal that has passed through the second band-pass filter 7 is converted into a second impedance conversion circuit 8
And output to the preamplifier 10. In the second impedance conversion circuit 8, the movable contact 6D of the changeover switch 6 is connected to the fixed contact 6 from the output terminal of the second bandpass filter 7.
The impedance of the circuit system including the wiring reaching the input terminal of the preamplifier 10 through C is reduced. As a result, the influence of noise that enters from the wiring of the circuit system, for example, the noise generated by the magnetic field of the built-in battery is reduced. At this time, a point P in FIG. 1 of the microphone including the circuit elements from the output terminal of the second bandpass filter 7 to the input terminal of the preamplifier 10
The frequency characteristic at is as shown by the characteristic curve 43 in FIG.

As described above, the output system of the omnidirectional microphone 2 is provided with the second band-pass filter 7 and the second impedance conversion circuit 8, and the output signal level of the second impedance conversion circuit 8 is attenuated by the attenuation level setting means 9. Therefore, the omnidirectional microphone 2 can be adapted for voice memos, and by bringing the mouth close to the omnidirectional microphone 2, it is possible to reliably record only the voice memo spoken by the user. Thus, the omnidirectional microphone 2 can be used for voice memo.

The microphone switching system of the present invention is not limited to those used in the performance mode, conference mode, and voice memo mode as shown in the above embodiment, but may be variously changed in accordance with other recording states and recording purposes. The sensitivity can be set for the mode and used.

[0022]

As described above, according to the present invention, unnecessary signal components such as background noise can be removed by incorporating a band-pass filter and an impedance conversion circuit into a directional microphone and an omnidirectional microphone. It is possible to use the directional microphone and the omnidirectional microphone in the specifications according to the recording environment and the recording purpose, such as performances, conferences and voice memos, even if the connection distance between the circuits is long, and it is optimal. This has the effect that a proper recording can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration in which a microphone switching system of the present invention is applied to a recording / reproducing device such as a tape recorder.

FIG. 2 is a circuit diagram showing a configuration of a microphone switching system according to the embodiment of the present invention.

FIG. 3 is a frequency characteristic diagram of a microphone during a performance, a conference, and voice memo recording according to the embodiment of the present invention.

[Explanation of symbols]

1 directional microphone, 2 omnidirectional microphone, 3 microphone amplifier (amplifier), 4 first bandpass filter, 5 first impedance conversion circuit,
6 ... Switches (switching means), 6A to 6C ... Fixed contacts, 6D ... Movable contacts, 7 ... Second band pass filter, 8 ... Second impedance conversion circuit, 9 ... Attenuation level setting means.

Claims (7)

[Claims] 1. A microphone switching system which, when picking up sound using directional and omnidirectional microphones, switches between these microphones and connects to an audio amplification means to enable accurate recording, wherein: A first band-pass filter connected to an output end of the directional microphone, for limiting a pass band of a frequency of an audio signal picked up by the directional microphone; and a first band-pass filter connected to an output end of the omni-directional microphone, A second band-pass filter for limiting a pass band of a frequency of an audio signal picked up by a microphone, and an attenuation level for setting an output signal passing through the second band-pass filter to a plurality of attenuation levels in accordance with a recording purpose. Setting means; a contact provided at an output end of the first band-pass filter; Switching means for switching and connecting an input terminal of the audio amplification means to a contact provided for each attenuation level of the filter setting means; and a switching means connected between an output terminal of the first band-pass filter and the contact provided at the output terminal. A first impedance conversion circuit that lowers the impedance of a circuit system reaching the input terminal of the audio amplification unit through the switching unit to reduce the influence on noise; and an output terminal of the second bandpass filter and the attenuation level setting unit. A second impedance conversion circuit that is connected between the input terminals and reduces an impedance of a circuit system reaching the input terminal of the audio amplification unit through the attenuation level setting unit and the switching unit to reduce an influence on noise. Characteristic microphone switching system. 2. An amplifier according to claim 1, wherein an amplifier for amplifying the audio signal picked up by said directional microphone is connected between an output terminal of said directional microphone and an input terminal of said band-pass filter. Microphone switching system. 3. The microphone switching system according to claim 1, wherein said first and second impedance conversion circuits are formed by emitter followers having high input impedance and low output impedance. 4. The microphone switching system according to claim 1, wherein said audio amplifier comprises a preamplifier and a power amplifier. 5. The attenuation level setting means comprises a plurality of resistors connected in series between an output terminal of the second impedance conversion circuit and ground, and each contact is connected to an output terminal of the second impedance conversion circuit. 2. The microphone switching system according to claim 1, wherein the microphone switching system is provided at a connection point between the resistors. 6. The directional microphone, when the switching means is switched and connected to an output terminal of the first impedance conversion circuit, functions as a sound pickup system suitable for recording only a sound in a specific direction. The microphone switching system according to claim 1 or 2, wherein: 7. The omnidirectional microphone functions as a sound pickup system suitable for conference recording or voice memo recording when the switching means is switched and connected to a terminal of the attenuation level setting means. 3. The microphone switching system according to 1 or 2.