Abstract: An acoustic impedance on a rear acoustic terminal side is set such that satisfactory directionality is obtained even in a high tone range. A rear portion of a sealing member 30A fitted to a unit case 10 is formed in a convex spherical shape, ranging from an apex part 301 to a hem part 302. The sealing member 30A forms an acoustic distributed constant circuit including: a first portion 310 in which a cross-sectional area of a sound path continuously increases, the sound path running from acoustic resistance parts AR as sound holes 28a of an electroacoustic transducer 20 to reach a rear acoustic terminal 12 through an air chamber A; and a second portion 320 on the rear acoustic terminal 12 side in which a cross-sectional area continuously decreases toward a direction farther from a sound pickup source.

Abstract: A dynamic microphone includes: a diaphragm; a voice coil fixed to the diaphragm; a magnetic circuit which includes a magnetic gap in which the voice coil is arranged and generates a magnetic field in the magnetic gap; a volume reducing member which is attached to the magnetic circuit, is arranged in a back surface space of the diaphragm, and reduces a volume in an air chamber in the back surface space; a communication passage which is formed along between the volume reducing member and the magnetic circuit and communicates the back surface space with a back side air chamber; and an acoustic resistance which is attached to the magnetic circuit and intervenes between the communication passage and the back side air chamber.

Abstract: Provided is an impedance conversion circuit of a condenser microphone which includes a first electron tube operated in grounded-cathode mode to whose grid an output signal from a condenser microphone unit is inputted, and from whose plate a signal is outputted, a first emitter-follower circuit configured to receive a signal based on a plate output of the first electron tube and amplify a current, and a first feedback element configured to transmit a feedback signal from an emitter of a transistor configuring the first emitter-follower circuit to the grid of the first electron tube.

Abstract: Provided is a variable directivity electret condenser microphone that can simplify a circuit configuration, and outputs an audio signal in an unbalanced manner. Included are electrically independent first and second electret condenser microphone units in which first and second fixed electrodes are arranged back to back and facing each other in a mutually non-conductive state, and first and second diaphragms are arranged facing the first and second fixed electrodes with fixed intervals from the first and second fixed electrodes, respectively, a first impedance converter having an input terminal connected to the first fixed electrode, a DC cut capacitor selectively connected between an output terminal of the first impedance converter and an input terminal of the second impedance converter, and a directivity variable switche that can alternatively select a mode from at least a first directivity mode to a third directivity mode.

Abstract: An acoustic tube attaching unit that attaches an acoustic tube to a side of a main body case where a microphone unit is mounted. The acoustic tube attaching unit includes first and second elastic members lying between a fixing member and a washer, and bolts that tight the fixing member and the washer in an axial direction. A peripheral edge surface of the first elastic member is formed in a linear manner, and a peripheral edge surface of the second elastic member is formed in a recessed surface manner, so that the peripheral edge surface of the first elastic member protrudes in an outer peripheral direction by elastic deformation by the tightening of the bolts. The acoustic tube is attached to the main body case side by fixing action to an inner wall of the acoustic tube by the protrusion of the first elastic member in the outer peripheral direction.

Abstract: A unidirectional condenser microphone unit is provided that have directionality unaffected by the external environment, and a method of manufacturing the unidirectional condenser microphone. The unidirectional condenser microphone unit having an interior and an exterior, the unidirectional condenser microphone includes a diaphragm, a fixed electrode facing the diaphragm, the fixed electrode constituting a capacitor with the diaphragm, an insulating base disposed in a back face side of the fixed electrode, the insulating base supporting the fixed electrode, an air chamber disposed in the back face side of the fixed electrode, and a gap disposed between the fixed electrode and the insulating base. The fixed electrode includes at least one sound hole in communication with the air chamber. The insulating base includes a communication hole establishing communication between the gap and the exterior of the microphone unit. The air chamber and the gap are in communication with each other.

Abstract: The orientation of the directional axis and the directionality of a microphone are adjusted through a simple configuration.

Abstract: To provide an impedance converter circuit for a condenser microphone which can secure a wide dynamic range using a voltage amplifier circuit. The impedance converter circuit is provided with: a first electron tube of a cathode grounded type in which an output signal of a condenser microphone unit is input into a grid and output from a plate; a second electron tube in which an output signal from the plate of the first electron tube is input into a grid and output from at least a cathode; and a feedback element configured to transmit a feedback signal from the cathode of the second electron tube to the grid of the first electron tube.

Abstract: An audio output circuit of a condenser microphone includes a condenser microphone unit, first and second impedance conversion circuits that receive a positive phase output signal and a reverse phase output signal from the condenser microphone unit, first and second output circuits that output an audio signal from the condenser microphone unit in a balanced line to a balanced output terminals upon receipt of outputs of the first and second impedance conversion circuits. First and second impedance conversion circuits respectively use FETs as source follower circuits and supply first and second impedance conversion outputs generated across source resistors to the first and second output circuits. A voltage regulating device that generates a constant voltage is connected in series to the source resistors. With this configuration, an audio output circuit of a condenser microphone is provided, which solves a problem of operation instability caused by variation of Idss's of the FETs.

Abstract: A microphone includes a microphone unit having a diaphragm vibrating in response to sound. The microphone unit converts the sound into an electrical signal. A cylindrical casing contains the microphone unit. A metal mesh strip rounded along the inner surface of the casing is attached to the inner surface of the main wall of the casing so as to cover openings. The rounded metal mesh strip has a spring portion generating spring force to expand the metal mesh strip against the inner surface of the casing to provide electrostatic shielding.

Abstract: A unidirectional condenser microphone includes a diaphragm, a fixed electrode disposed opposite a back face of the diaphragm and an electrode extraction part for the fixed electrode disposed at a backside of the fixed electrode and having a through hole adapted to capture a sound wave from a rear acoustic terminal into a backside of the diaphragm. The through hole has a horn-shaped opening formed in continuation of the through hole at the rear acoustic terminal side thereof such that an inner diameter of the horn-shaped opening is increased toward the rear acoustic terminal side. The electrode extraction part has a plurality of the through holes formed therein at regular intervals along a concentric circle around an axial center of the electrode extraction part, and all the through holes along the concentric circle have the horn-shaped openings formed therein, respectively.

Abstract: A dynamic microphone which prevents a wall forming a back-side air chamber from having a certain resonance frequency and effectively prevents the generation of standing waves in the back-side air chamber is provided. A dynamic microphone includes a dynamic microphone unit including a diaphragm configured with a voice coil and a magnetic circuit having a magnetic gap provided so as to allow the voice coil to vibrate, a bottomed case which is coupled to the dynamic microphone unit and forms a back-side air chamber communicating with back side of the diaphragm, and an acoustic resistance body which is pressingly attached in the case and composed of metal fiber including a pocket, an open cross sectional area of the pocket gradually decreasing toward the direction remote from the dynamic microphone unit.

Abstract: A boundary microphone includes a microphone and a boundary plate on which the microphone is placed. The boundary plate includes a porous metal material of an aluminum-based metallic fiber layer clamped by an aluminum-based expanded metal and crimped thereto. The boundary plate has a characteristic of absorbing an incoming sound wave without reflecting the sound wave to the microphone, and the microphone collects a direct sound.

Abstract: A microphone device includes an audio signal output circuit that balanced-outputs, through a balanced transmission line, an audio signal output from a condenser microphone unit, a balanced output terminal including a hot terminal, a cold terminal, and a ground terminal connected to the balanced transmission line, a power supply circuit that supplies a phantom power supply to the audio output circuit from the balanced output terminal through the balanced transmission line, and a display circuit including light emitting elements that perform lighting and non-lighting according to an operation of a manual switch, and the display circuit includes constant current elements that generate a constant current through the balanced transmission line, a constant voltage element connected to the constant current elements and which generates a constant voltage, and light emitting elements connected to the constant current elements, and to which the constant voltage by the constant voltage element is applied.

Abstract: There are provided a microphone stand having a connector supporting groove, and a microphone body supported by the microphone stand as a result of insertion of a connector case into the connector supporting groove. A resilient conductive cloth which comes into contact with the connector case is arranged in the connector supporting groove, with the connector case inserted in the connector supporting groove. The conductive cloth is preferably arranged in a ring shape along a lower bottom portion of the annularly formed connector supporting groove. This configuration mitigates rattling generated between the connector supporting groove and the connector case, thereby suppressing generation of a vibration noise due to microphone shaking.

Abstract: A unidirectional condenser microphone having a front opening portion and a rear opening portion for respectively passing sound waves to a front surface and a back surface of a diaphragm of a microphone unit, the unidirectional condenser microphone includes: an acoustic tube provided in the front opening portion; a first air chamber provided between the rear opening portion and the back surface of the diaphragm of the microphone unit, and having a predetermined acoustic capacity; and a second air chamber communicating into the first air chamber, and having an acoustic capacity larger than the predetermined acoustic capacity, wherein sensitivity to a direction of 0° with respect to a directional axis is improved by the first air chamber and the acoustic tube, and a proximity effect due to the sound wave from a direction of 180° with respect to the directional axis is prevented by the second air chamber.

Abstract: A non-directional microphone includes a housing, a microphone unit attached to the housing, and including a diaphragm that receives a sound wave, and a connector portion to which a cable connector including a cable that transmits an audio signal from the microphone unit is connected, and a pressure equalization opening that allows a back-side space of the diaphragm in the housing and an outer space to communicate is provided in the connector portion. In the non-directional microphone, the communication between the back-side space of the diaphragm and the outer space through the pressure equalization opening is cut off when the cable connector is connected to the connector portion, and the back-side space of the diaphragm communicates into the outer space through the pressure equalization opening when the cable connector is disconnected from the connector portion.

Abstract: An electrode extraction terminal extracting a generated current by contacting with a fixed electrode is disposed inside a unit case, and can change from a cardioid to a hyper cardioid. The electrode extraction terminal includes an electrode rod portion having a projection portion at a tip side; and a pedestal portion having a flat surface surrounded by a peripheral wall portion having a sitting height thereof same as that of the projection portion of the electrode rod portion, and facing the fixed electrode under a shape with a size showing a cardioid in directivity, wherein the flat surface is located orthogonal to an axis direction of the electrode rod portion. In a peripheral surface area of one or more sound holes of the flat surface, a minute concave-convex surface is provided to reduce an acoustic resistance value to show a hyper cardioid in directivity.

Abstract: A microphone includes a tubular first and second acoustic tubes configured with a gap between the second acoustic tube and an inner side of the wall surface of the first acoustic tube. A first opening portion is provided in a wall surface of the first acoustic tube. A second opening portion is provided in a wall surface of the second acoustic tube. A microphone unit is provided inside the second acoustic tube and is configured to acquire sound waves from outside the microphone. A sound wave introduction path formed by the first opening portion, the gap, and the second opening portion, is configured to transmit the sound wave from the outside to the microphone unit.

Abstract: A diaphragm is provided that has small mechanical anisotropy even when heat is applied to the diaphragm in the production process. The diaphragm includes a biaxially stretched film stretched in a first direction (the machine direction) and a second direction (the transverse direction), wherein the entire surface of the biaxially stretched film has a first pattern and a second pattern, the first pattern has ridges and grooves with a first pitch, the second pattern has ridges and grooves with a second pitch, the second pitch is smaller than the first pitch, the second pattern is formed along the first direction or the second direction, and the length of regions defined by the first pattern in the first direction differs from the length of the regions in the second direction.