JP5281968B2 - Measuring method of acoustic characteristics of dynamic microphone unit - Google Patents

Description

  The present invention relates to a method for measuring acoustic characteristics of a dynamic microphone unit. More specifically, the present invention does not require expensive measurement equipment such as an anechoic room or a soundproof room, and even in an environment where noise exists in the surroundings, the dynamic microphone can be used. The present invention relates to a technique capable of measuring the acoustic characteristics of a unit.

  In order to measure the acoustic characteristics of a dynamic microphone unit, for example, as described in Patent Document 1, a sound wave is applied to a dynamic microphone unit to be measured from a speaker, and an electric signal generated in the voice coil is read with a level meter. I have to.

  However, in this measurement method, an anechoic room or a soundproof room is required in order to avoid the influence of standing waves and reflected waves existing in the measurement environment.

  Moreover, even if it is a speaker to be used, since the frequency response is not flat, the apparatus which correct | amends and measures this is required. Thus, in the case of the above-described measurement method, it is necessary to prepare expensive measurement equipment and measuring instruments such as an anechoic room and a soundproof room (see EIAJ RC-8160A).

  Even if measurement equipment such as an anechoic room or a soundproof room is in place, every time an acoustic characteristic is measured, it must be removed from the assembly line and the product must be brought into the anechoic room or soundproof room. There is a problem of requiring labor and time.

JP 59-75126 A

  Therefore, an object of the present invention is to make it possible to measure the acoustic characteristics of a dynamic microphone unit even in an environment where noise exists in the surroundings without requiring expensive measurement equipment such as an anechoic room or a soundproof room. There is.

  In order to solve the above-mentioned problem, a first invention of the present application is that a diaphragm having a voice coil and a magnetic circuit for providing a magnetic gap to the voice coil are supported by a unit frame, and the magnetic circuit in the unit frame is provided. An acoustic characteristic measurement method for a dynamic microphone unit that measures an acoustic characteristic of a dynamic microphone unit in which an acoustic resistance material that controls an omnidirectional component is arranged on the rear side of the bottomed cylindrical shape having an omnidirectional microphone inside A measurement housing is hermetically fitted to the rear end of the unit frame to form an air chamber having a predetermined volume, and a measurement signal having a predetermined frequency is applied from an oscillator to the voice coil to vibrate the diaphragm. The sound wave that enters the air chamber through the acoustic resistance material is picked up by the omnidirectional microphone, and the sound pressure level is obtained. Ri is characterized by measuring the acoustic characteristics of the dynamic microphone unit.

  According to a second aspect of the present invention, a diaphragm having a voice coil and a magnetic circuit for providing a magnetic gap to the voice coil are supported by a unit frame, and are not disposed on the rear side of the magnetic circuit in the unit frame. One end side of a cylindrical measurement housing having an omnidirectional microphone in the dynamic microphone unit acoustic characteristic measurement method for measuring the acoustic characteristics of a dynamic microphone unit in which an acoustic resistance material that controls a directional component is arranged In addition, the rear end portion of the unit frame of the reference dynamic microphone unit with known acoustic characteristics is hermetically fitted, and the rear end portion of the unit frame of the dynamic microphone unit to be measured is connected to the other end side of the measurement housing. To form an air chamber with a predetermined volume in the measurement housing A measurement signal having a predetermined frequency is generated, and the measurement signal is given as a normal phase to one of the voice coils of each of the dynamic microphone units, and the measurement signal is given as a negative phase to the other voice coil. The diaphragm of each dynamic microphone unit is vibrated, the sound pressure in the air chamber is measured by the omnidirectional microphone, and the acoustic characteristics of the dynamic microphone unit to be measured are measured by the output level. .

  In the first and second inventions, an omnidirectional condenser microphone is preferably used as the omnidirectional microphone.

  According to the first and second inventions, the measurement housing in which the sound-collecting omnidirectional microphone is arranged is almost sealed during measurement, and therefore, in an environment where noise exists in the surroundings. However, it is possible to accurately measure the acoustic characteristics of the dynamic microphone unit.

  Moreover, according to 1st invention, it can be determined whether the acoustic resistance value of the acoustic resistance material which manages a non-directional component especially is appropriate.

  Further, according to the second invention, it is possible to determine whether the acoustic characteristics of the entire dynamic microphone unit to be measured are good or bad by comparing with the acoustic characteristics of the reference dynamic microphone unit.

Sectional drawing which shows the measurement state of the acoustic characteristic by 1st Embodiment of this invention. Sectional drawing which shows the measurement state of the acoustic characteristic by 2nd Embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2, but the present invention is not limited to this.

  First, the acoustic characteristic measurement method according to the first embodiment of the present invention will be described with reference to FIG. 1. Prior to that, the configuration of the dynamic microphone unit 1 will be schematically described.

  As a basic configuration, the dynamic microphone unit 1 includes a diaphragm 10, a magnetic circuit 20, and a unit frame 30 that supports them.

  The diaphragm 10 includes a center dome 11, a sub dome 12 formed around the center dome 11, and a voice coil 13 bonded and fixed to the back side of the diaphragm 10 at the boundary between the center dome 11 and the sub dome 12. It is configured.

  The magnetic circuit 20 includes a yoke 21 having a shallow bottom cup shape, a disk-like permanent magnet 22 disposed substantially at the center of the bottom surface of the yoke 21, a center hole piece 23 disposed on the permanent magnet 22, a yoke The ring yoke 24 is arranged at the upper end of the ring 21 and forms an annular magnetic gap with the center hole piece 23.

  The unit frame 30 is formed in a substantially cylindrical shape by an electrical insulating material such as synthetic resin or ceramic, and supports the diaphragm 10 and the magnetic circuit 20 on the front end side (left side in FIG. 1).

  The magnetic circuit 20 is fixedly arranged at the center of the front end side of the unit frame 30, whereas the diaphragm 10 is arranged so that the voice coil 13 can vibrate within the magnetic gap of the magnetic circuit 20. 12 peripheral portions are supported on the front end side of the unit frame 30.

  A resonator 14 having a front acoustic terminal 15 is attached to the front end side of the unit frame 30 so as to cover the front surface of the diaphragm 10.

  Since the dynamic microphone unit 1 in this embodiment is unidirectional, the unit frame 30 includes a rear acoustic terminal 31 for allowing sound waves from a sound source (not shown) to act on the back side of the diaphragm 10. .

  The dynamic microphone unit 1 is provided with an air chamber (rear air chamber) on the rear side of the unit frame 30 regardless of whether it is unidirectional or omnidirectional.

  The air chamber is formed by a microphone grip (microphone casing) or a middle cylinder that is disposed in the microphone grip and is fitted to the rear end portion 30a of the unit frame 30, and will be described later when measuring acoustic characteristics. It is formed by the measurement casing 41 (or 51).

  In order to communicate the air chamber with the back side of the diaphragm 10, a sound hole (a hole through which sound is passed) 21 a is formed at the bottom of the yoke 21 of the magnetic circuit 20. An acoustic resistance material 32 that controls an omnidirectional component is disposed on the bottom side.

  As the acoustic resistance material 32, a felt material or an open-cell sponge material is usually used, and the omnidirectional component depends on the acoustic resistance value.

  Therefore, by making the acoustic resistance value of the acoustic resistance material 32 constant, a dynamic microphone unit having uniform acoustic characteristics can be produced regardless of omnidirectionality and unidirectionality. The resistance value often tends to vary.

  In the unidirectional dynamic microphone unit, the bidirectional component is controlled by the acoustic mass of the rear acoustic terminal 31. The acoustic mass of the rear acoustic terminal 31 can be made stable by making the mechanical dimensions of the acoustic terminal uniform, and hardly varies compared to the acoustic resistance material 32.

  In the first embodiment, the acoustic resistance value of the acoustic resistance material 32 incorporated mainly in the dynamic microphone unit 1 is measured. Therefore, a measurement housing 41, an omnidirectional microphone 42, an oscillator (oscillator) 43, a level meter (not shown), and the like are used.

  The measurement housing 41 has a bottomed cylindrical shape, and forms an air chamber 41 a at the rear part of the dynamic microphone unit 1. The material may be metal, synthetic resin, ceramics, or the like.

  The omnidirectional microphone (hereinafter, simply referred to as “microphone”) 42 is a microphone that collects sound waves that pass through the acoustic resistance material 32 and enter the air chamber 41a, and an omnidirectional condenser microphone is preferably used. . The microphone 42 is set in the measurement housing 41 in advance, and the microphone cord 42a is drawn out of the measurement housing 41 through the airtight hole.

  The oscillator 43 is connected to the voice coil 13 of the diaphragm 10. Since the coil end of the voice coil 13 is soldered to a terminal portion (not shown) of the circuit board 33 disposed on the body portion of the unit frame 30, the oscillator 43 may be connected to the terminal portion of the circuit board 33. .

  In order to measure acoustic characteristics, as shown in FIG. 1, a measurement housing 41 is airtightly fitted to the rear end portion 30 a of the unit frame 30, and an air chamber having a predetermined volume is provided at the rear portion of the dynamic microphone unit 1. After forming 41 a, a measurement signal is supplied from the oscillator 43 to the voice coil 13 to vibrate the diaphragm 10.

  Sound waves generated thereby pass through the acoustic resistance member 32 and enter the air chamber 41a. The sound pressure depends on the acoustic resistance value of the acoustic resistance material 32.

  Therefore, sound waves that pass through the acoustic resistance material 32 and enter the air chamber 41a are collected by the microphone 42, and the sound pressure level of the acoustic resistance material 32 is measured by measuring the sound pressure level with a level meter (not shown). Pass / fail can be determined.

  Next, a second embodiment will be described with reference to FIG. In the second embodiment, the reference dynamic microphone unit with known acoustic characteristics (non-defective) is 1S, the dynamic microphone unit to be measured is 1M, and 1S and 1M are compared to measure the 1M acoustic characteristics.

  Therefore, in the second embodiment, a cylindrical measurement casing 51 having both ends opened is used as the measurement casing. A microphone 42 is set in the measurement housing 51 as in the first embodiment.

  Further, a measurement signal is supplied from the oscillator 43 to each voice coil 13 of the dynamic microphone units 1S and 1M. However, in order to operate differentially, the measurement signal output from the oscillator 43 is directly applied to one voice coil 13. Whereas the normal phase is supplied, the measurement signal is supplied to the other voice coil 13 as a reverse phase signal whose phase is inverted by the phase inversion circuit 43a.

  Since the dynamic microphone units 1S and 1M have the configuration described in FIG. 1, the description thereof is omitted. However, when it is necessary to distinguish between the reference side and the measured side for the constituent elements, S and M are added to the reference symbols.

  To measure the acoustic characteristics, as shown in FIG. 2, the reference dynamic microphone unit 1S is airtightly fitted to one end side (in this example, the left end side in FIG. 2) of the measurement casing 51, and the measurement target The dynamic microphone unit 1M is hermetically fitted to the other end side of the measurement casing 51 (in this example, the right end side in FIG. 2), and the measurement chamber 51 has an air chamber 51a common to both microphone units. And

  The dynamic microphone unit 1M to be measured is detachable from the measurement housing 51, but the reference dynamic microphone unit 1S may be fixed to the measurement housing 51 with screws or an adhesive.

  When a measurement signal is output from the oscillator 43 and the dynamic microphone units 1S and 1M are driven, the reference-side diaphragm 10S and the measured-side diaphragm 10M vibrate with the same vibration direction. That is, in FIG. 2, if the diaphragm 10S moves to the left, the diaphragm 10M also moves to the left, and if the diaphragm 10S moves to the right, the diaphragm 10M also moves to the right.

  Therefore, if the amplitudes of the diaphragms 10S and 10M, the acoustic resistance values of the acoustic resistance members 32S and 32M, and the like are aligned, the sound pressure in the air chamber 51a hardly fluctuates, so the output level of the microphone 42 is also low. Thereby, it can be determined that the measured dynamic microphone unit 1M has the same acoustic characteristics as the reference dynamic microphone unit 1S.

  As described above, in both cases of the first embodiment and the second embodiment, since the microphone 42 is disposed in the air chambers 41a and 51a, it is not affected by ambient noise or noise. The acoustic characteristics can be measured.

  Therefore, it is possible to easily and accurately determine the quality of a unit manufactured on a noisy or noisy assembly line. Items that can be measured by the present invention include sensitivity, directivity, low frequency response, polarity of moving diaphragm, and the like.

DESCRIPTION OF SYMBOLS 1 Dynamic microphone unit 1S Reference | standard dynamic microphone unit 1M Dynamic dynamic unit to be measured 10 Diaphragm 15 Front acoustic terminal 20 Magnetic circuit 30 Unit frame 31 Rear acoustic terminal 32 Acoustic resistance material 41, 51 Measuring housing 41a, 51a Air chamber 42 Omnidirectional microphone 43 Oscillator

Claims (3)

A diaphragm having a voice coil and a magnetic circuit that provides a magnetic gap to the voice coil are supported by a unit frame, and an acoustic resistance material that controls an omnidirectional component is disposed on the rear side of the magnetic circuit in the unit frame. In the method for measuring the acoustic characteristics of a dynamic microphone unit for measuring the acoustic characteristics of a dynamic microphone unit,
A bottomed cylindrical measurement housing having an omnidirectional microphone inside is hermetically fitted to the rear end of the unit frame to form an air chamber of a predetermined volume, and a predetermined volume is provided from the oscillator to the voice coil. A frequency measurement signal is applied to vibrate the diaphragm, and sound waves that enter the air chamber via the acoustic resistance material are collected by the omnidirectional microphone. The acoustic characteristics of the dynamic microphone unit are determined by the sound pressure level. A method for measuring the acoustic characteristics of a dynamic microphone unit, characterized in that A diaphragm having a voice coil and a magnetic circuit that provides a magnetic gap to the voice coil are supported by a unit frame, and an acoustic resistance material that controls an omnidirectional component is disposed on the rear side of the magnetic circuit in the unit frame. In the method for measuring the acoustic characteristics of a dynamic microphone unit that measures the acoustic characteristics of a dynamic microphone unit,
A rear end portion of a unit frame of a reference dynamic microphone unit with known acoustic characteristics is hermetically fitted to one end side of a cylindrical measurement housing having an omnidirectional microphone inside, and the measurement housing described above The other end of the unit is hermetically fitted with the rear end of the unit frame of the dynamic microphone unit to be measured to form an air chamber having a predetermined volume in the measurement housing,
A measurement signal of a predetermined frequency is generated from an oscillator, and the measurement signal is given as a normal phase to one of the voice coils of each of the dynamic microphone units, and the measurement signal is given as a negative phase to the other voice coil. And vibrating the diaphragm of each dynamic microphone unit, measuring the sound pressure in the air chamber with the omnidirectional microphone, and measuring the acoustic characteristics of the measured dynamic microphone unit based on the output level. To measure the acoustic characteristics of a dynamic microphone unit.   The method for measuring acoustic characteristics of a dynamic microphone unit according to claim 1 or 2, wherein a non-directional condenser microphone is used as the non-directional microphone.

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