Unidirectional microphone

Abstract

To obtain a unidirectional microphone with high sound quality, which achieves unidirectivity while preventing deterioration in sound quality of a ribbon microphone. A unidirectional condenser microphone and bi-directional ribbon microphones are included, and the unidirectional condenser microphone and the bi-directional ribbon microphones are disposed such that a 0 direction of a sound collecting axis of the unidirectional condenser microphone accords with a 180 direction of sound collecting axes of the bi-directional ribbon microphones, and an output of the unidirectional condenser microphone is subtracted from an output of the 180 direction of the bi-directional ribbon microphones.

Claims

1. A unidirectional microphone comprising: a unidirectional condenser microphone; and a bi-directional ribbon microphone, wherein the unidirectional condenser microphone and the bi-directional ribbon microphone are arranged such that a 0 direction of a sound collecting axis of the unidirectional condenser microphone accords with a 180 direction of a sound collecting axis of the bi-directional ribbon microphone, and an output of the unidirectional condenser microphone is subtracted from an output of the 180 direction of the bi-directional ribbon microphone, and only the bi-directional ribbon microphone has a sensitivity for a sound wave from the 0 direction of the sound collecting axis of the bi-directional ribbon microphone.

2. The unidirectional microphone according to claim 1, wherein the bi-directional ribbon microphone includes two bi-directional ribbon microphones disposed laterally symmetric to the unidirectional condenser microphone.

3. The unidirectional microphone according to claim 2, wherein the output of the unidirectional condenser microphone and outputs of the bi-directional ribbon microphones are outputted as a balanced output.

4. The unidirectional microphone according to claim 1, wherein the bi-directional ribbon microphone includes two bi-directional ribbon microphones arranged in parallel to each other, and the condenser microphone is arranged between the two bi-directional ribbon microphones.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a front view (a view as viewed from a 180 side of a sound collecting axis) of a unidirectional microphone according to the present invention;

(2) FIG. 2 is a plan view of the unidirectional microphone of FIG. 1;

(3) FIG. 3 is a side view of the unidirectional microphone of FIG. 1;

(4) FIG. 4A is a circuit diagram of the unidirectional microphone of FIG. 1;

(5) FIG. 4B is a circuit diagram of the unidirectional microphone of FIG. 1 for another example;

(6) FIGS. 5A to 5C are graphs of directional frequency characteristics of microphone elements that constitute the unidirectional microphone of FIG. 1; and

(7) FIGS. 6A to 6C are graphs of directional frequency characteristics of a bi-directional ribbon microphone element and a non-directional condenser microphone element that constitute a conventional unidirectional microphone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view (a view as viewed from a 180 side of a sound collecting axis) of a unidirectional microphone according to the present invention, FIG. 2 is a plan view, and FIG. 3 is a side view. Further, FIGS. 4A and 4B are circuit diagrams of this unidirectional microphone 1.

(9) As illustrated in the drawings, the unidirectional microphone 1 includes one unidirectional condenser microphone 2, and two bi-directional ribbon microphones 3 and 4 which are symmetrically disposed to hold the unidirectional condenser microphone 2 therebetween (only one of the ribbon microphones is illustrated in FIG. 4A). The two bi-directional ribbon microphones 3 and 4 are electrically connected in series. FIG. 4B further shows a circuit diagram that includes two bidirectional ribbon microphones 3 and 4 connected in series.

(10) To be specific, the bi-directional ribbon microphones 3 and 4 and the unidirectional condenser microphone 2 are arranged such that a 0 direction of a sound collecting axis of the unidirectional condenser microphone 2 accords with a 180 direction of sound collecting axes of the bi-directional ribbon microphones 3 and 4, and an output of the unidirectional condenser microphone 2 is subtracted from outputs of the bi-directional ribbon microphones 3 and 4.

(11) FIGS. 5A, 5B, and 5C illustrate graphs of directional frequency characteristics of the respective microphones. FIG. 5A illustrates the directional frequency characteristics of the bi-directional ribbon microphones 3 and 4, FIG. 5B illustrates the directional frequency characteristics of the unidirectional condenser microphone 2, and FIG. 5C illustrates the directional frequency characteristics of the unidirectional microphone 1, where the output of the unidirectional microphone 1 is a differential output of the circuits shown in FIGS. 4A and 4B.

(12) As illustrated in FIG. 5B, the unidirectional condenser microphone 2 has no response in a direction corresponding to the 0 direction illustrated in FIG. 5A of the sound collecting axes of the bi-directional ribbon microphones 3 and 4. That is, the unidirectional condenser microphone 2 has no response in a direction corresponding to 180 of the sound collecting axis. Therefore, as illustrated in FIG. 5C, the outputs in the 180 direction of the sound collecting axes of the bi-directional ribbon microphones 3 and 4 decreases in an output of the unidirectional microphone 1, and as a result unidirectivity is achieved.

(13) That is, only the bi-directional ribbon microphones 3 and 4 have sensitivity for a sound wave from the 0 direction of the sound collecting axes of the bi-directional ribbon microphones 3 and 4.

(14) In terms of the circuit diagram of FIG. 4, an output (PIN 3) of the unidirectional condenser microphone 2 and outputs (PINs 2) of the bi-directional ribbon microphones 3 and 4 are balanced output, and are differentially inputted to a mixer (not shown), and a subtraction output can be obtained from the mixer. The output voltages of the bi-directional ribbon microphones 3 and 4 are boosted up by a transformer T, and are outputted to the PINs 2. Note that a PIN 1 is a ground potential (GND), and one terminal of the unidirectional condenser microphone 2 and one terminal of the transformer T are connected to the ground potential.

(15) According to the present embodiment, since the output of the unidirectional condenser microphone 2 is subtracted from the outputs in the 180 direction of the sound collecting axes of the bi-directional ribbon microphones 3 and 4, this configuration allows to achieve the unidirectivity without impairing the sound quality of the ribbon microphones. Further, use of the unidirectional microphone for amplification can prevent howling.

(16) Note that, in the above-described embodiment, the two bi-directional ribbon microphones 3 and 4 are disposed laterally symmetric to the one condenser microphone 2. However, the present invention is not limited to the configuration, and a configuration using one bi-directional ribbon microphone may be employed.

(17) Further, the unidirectional microphone 1 according to the present invention is not limited in its use forms and can be favorably used for portable microphones, stand microphones, and the like.