JP2008256433A - Microphone unit, noise meter, and acoustic calibration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically adjust output and sensitivity following surrounding temperature changes, without making the structure of a microphone complex, and to maintain high-precision output, in response to environmental changes. <P>SOLUTION: To both ends of a feedback resistor R2, signal lines from a thermistor 32 are connected. Namely, a feedback resistance element results where the feedback resistor R2 and the thermistor 32 are connected in parallel. This thermistor 32 is attached to the periphery of a case 12 and its cartridge section 16-side end (side of a diaphragm 14). The thermistor 32 monitors ambient temperature at all times. That is, since the thermistor 32 changes its resistance value R3, in response to a change in the temperature of the thermistor 32, the resistance value of the feedback resistance element changes, gain is adjusted, and the output level can be adjusted and controlled in a preamplifier section 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention minimizes variations in the initial sensitivity (output) of the microphone and makes the sensitivity (output) constant with respect to ambient environment changes, particularly temperature changes, and the microphone or technology. It relates to sound level meter and sound calibrator.

  In general, condenser microphones or electret condenser microphones operate relatively stably with respect to ambient environmental conditions for structural reasons, but their sensitivity changes with changes in environmental conditions, particularly with changes in ambient temperature. In particular, inexpensive electret condenser microphones are not suitable for measuring instruments because of large variations and fluctuations in initial sensitivity.

  In general, condenser microphones and electret condenser microphones with a relatively stable output are used for sound level meters, but especially in the case of electret condenser microphones, the output and sensitivity to large changes in the ambient environment, especially temperature changes. Shows a change that cannot be ignored, and when it is used in a sound level meter as a “measuring instrument” or an acoustic calibrator (calibrator) for calibrating it, it becomes useless.

  Mainly used in these products are condenser microphones that are relatively stable to ambient environmental conditions.

  A microphone unit usually has a low-noise preamplifier attached to the microphone cartridge, so that the output of the unit is kept constant with respect to the ambient temperature, except to select individuals with sensitivity and characteristics that fall within the specified range as much as possible. Configuration and control are not included.

  An application example of a microphone is a sound level meter. For this sound level meter, there is no ingenuity or consideration to effectively absorb changes in environmental conditions other than selecting a condenser microphone with stable output and sensitivity.

Furthermore, the proposal of patent document 1 is made | formed as an acoustic calibrator which comprises the sensitivity of a measurement microphone or a sound level meter. In Patent Document 1, the sound generation level of a sound generator (electromagnetic earphone) is controlled so as to be stable against changes in atmospheric pressure-atmospheric pressure. Specifically, a calibrator is inserted vertically and quietly into the microphone unit portion of the sound level meter, and a switch is turned on to generate a specified calibration sound pressure.
JP 2001-349773 A

  However, in each of the condenser microphone unit, the sound level meter, and the sound calibrator, there are concerns about the following.

(Condenser microphone unit alone)
(1) Normally, the preamplifier is limited to a function of amplifying the signal output from the cartridge section or converting the impedance, and little consideration is given to changes in the surrounding environment.
(2) When these are incorporated into a measuring instrument such as a sound level meter, in general measurement, the standard of any “industrial class” (Tables 1 to 3) according to the relatively stable temperature characteristics of condenser microphones. The output / sensitivity often changes by several dB or more under a low temperature such as −10 ° C. or lower or a high temperature such as + 40 ° C. or higher.

  However, combinations of ambient temperature and relative humidity that are above + 39 ° C and exceed the dew point are excluded from the suitability evaluation test.

  The range of environmental conditions in the class 1 and class 2 acoustic calibrators is the same as the range in the class 1 and class 2 sound level meters defined in IEC 61672-1.

(noise meter)
(1) When trying to increase the stability of a condenser microphone used to avoid changes in environmental conditions, there was a tendency that the cost would be very high or the yield would be extremely poor.
(2) In order to lower the measurement lower limit of noise level / sound pressure level due to self-noise, the accuracy of the correction itself when the output sensitivity changes depending on the ambient environment in relation to the method of correcting the self-noise by storing it in memory beforehand. Will fall.

(Acoustic calibrator)
(1) Most commercially available products that use only stable sound generators (speakers, electromagnetic earphones, etc.) are not excessive at room temperature, but the efficiency of sound generators changes at very high temperatures and low frequencies. At the same time, the specified output (specified sound pressure) also fluctuates, and there is a dislike that the basic performance cannot be secured.
(2) Among commercially available products that are oriented toward high accuracy, there is a type as shown in FIG. 5 that controls the output of the sound generator in accordance with changes in atmospheric pressure. In this example, however, factors other than atmospheric pressure, such as temperature, are used. There is no means for detecting and correcting when the sound generation level (specified sound pressure) fluctuates due to changes or the like.
(3) Since there is no feedback control (feedback type control) or a circuit for controlling the output fluctuation, there remains a problem that it is weak against a large environmental change.

  In consideration of the above facts, the present invention can automatically adjust the output following the ambient temperature change without complicating the structure, and can maintain a highly accurate output against environmental changes. The purpose is to obtain a microphone unit, a sound level meter, and an acoustic calibrator.

  A first invention is a microphone unit having a cartridge part having a diaphragm for converting sound, which is a wave that fluctuates in pressure, into an electric signal, and a preamplifier part for amplifying the electric signal obtained by the diaphragm. Initial sensitivity correction means for correcting the initial gain with respect to the amplification factor in the preamplifier unit, a temperature detection sensor for detecting the temperature in the vicinity of the cartridge unit or the preamplifier unit, and the temperature detection Output correction means for correcting the output from the preamplifier unit based on the output from the sensor.

  The second invention has a cartridge part provided with a diaphragm for converting sound, which is a wave that fluctuates in pressure, into an electric signal, and a preamplifier part that amplifies the electric signal obtained by the diaphragm, A microphone unit whose initial sensitivity is corrected with reference to a predetermined steady temperature as an amplification factor in the preamplifier unit, a temperature detection sensor for detecting a temperature in the vicinity of the cartridge unit or the preamplifier unit, and the temperature detection sensor Output correcting means for correcting the output from the preamplifier unit based on the output from the preamplifier.

  In the first invention or the second invention, the microphone unit is configured as a condenser microphone or an electret condenser microphone.

  In the first invention or the second invention, the temperature sensor is a thermistor or a semiconductor temperature sensor, and the selection of the thermistor or the semiconductor temperature sensor is based on the temperature characteristics of the thermistor or the semiconductor temperature sensor, and the preamplifier unit. It is characterized by being dependent on the correlation with the temperature characteristics of the output.

  According to a third aspect of the present invention, there is provided a sound level meter for detecting noise, wherein the microphone unit according to any one of the first to fourth aspects is incorporated.

  According to a fourth aspect of the present invention, a sounding body is built in, and an output monitoring microphone is arranged in the vicinity of the sounding body, and the sound output of the sounding body is constantly monitored and controlled by the output of the output monitoring microphone, so that it is always constant. It is to provide an acoustic calibrator configured to generate a calibrated sound pressure. In addition, a microphone unit or a coupler unit for mounting an object to be inspected including a sound level meter, which is an acoustic calibrator for calibrating the sensitivity of the object to be inspected, detects a temperature in the vicinity of the sound calibrator. Output correction means for maintaining the acoustic output of the output monitoring microphone constant with respect to temperature change by a detection sensor and correcting the acoustic output of the sounding body based on the microphone output.

  In the fourth aspect of the invention, a battery is used as a power source, and when the battery is exhausted and the power supply voltage falls below an allowable range, the battery further includes warning means for warning both by display means and sound generation stop. It is a feature.

  In the fourth invention, the temperature sensor is a thermistor or a semiconductor temperature sensor, and the selection of the thermistor depends on the correlation between the temperature characteristic of the thermistor and the output temperature characteristic of the monitoring microphone. It is characterized by.

  Hereinafter, the common elements of the first to fourth inventions are collectively referred to as “the present invention”.

  According to the present invention, even if an inexpensive microphone such as an ECM (electret condenser microphone) is used, attention is paid to the fact that the temperature characteristic (temperature gradient) itself is stable with respect to variations in initial sensitivity. However, it is possible to provide a very advanced microphone unit that is stable against environmental changes.

  In addition, since the aspect of the present invention is strong as a basic elemental technology, from the viewpoint of use of the technology, the present invention is widely used for acoustic measuring instruments such as the above-mentioned sound level meter and acoustic calibrators such as a microphone calibration calibrator. it can.

(History focusing on variations in initial sensitivity and temperature characteristics (temperature gradient) itself are stable in time)
In the present invention, for example, at room temperature (around 20 ° C.), the sensitivity varies from individual to individual, or changes that cannot be ignored with respect to temperature, but the manner of change is almost constant. Focusing on this point and this property, the sensitivity and output of the unit (system) are always constant with respect to temperature changes.

  That is, in the present invention, the initial sensitivity of the condenser microphone itself and the change in temperature itself (temperature characteristics / gradient) are time-measured with respect to variations in the initial sensitivity of microphone production and output fluctuations due to ambient environmental conditions (especially temperature). Focusing on the fact that the temperature is almost constant, the temperature change is detected and corrected electrically, minimizing the variation in the initial sensitivity of each individual, and at the same time the sensitivity to the ambient environment change (temperature) is always It is intended to be constant.

  As a result, the following effects can be derived.

(General)
(1) Since the sensitivity is controlled by temperature detecting means installed inside or outside the diaphragm, it is possible to provide a microphone unit having very stable characteristics against environmental changes, particularly temperature changes.
(2) Since the detected temperature (change) and the initial sensitivity of the microphone are corrected simultaneously, as long as the initial sensitivity and temperature gradient are stable in time, a high-performance microphone unit can be constructed even if an inexpensive microphone is used. it can.
(3) Since the electret condenser microphone is adjusted and manufactured without applying a large tension to the diaphragm, even if the initial sensitivity and temperature change are large, this correction method has characteristics that surpass the expensive measurement condenser microphone. can get.
(4) If this technology and a microphone unit are installed, acoustic instruments such as sound level meters can be provided at low cost and high performance. However, digital acoustic instruments are numerically (software-like). Because it is possible to do this, it is possible to make corrections with higher precision and finer details. For repairs and replacements of microphones, it is only necessary to rewrite the correction constant table stored in the nonvolatile memory such as CMOS. .
(5) Also, in an acoustic calibrator equipped with this technology and a microphone unit, the output pressure of the sounding body is controlled by correctly detecting the sound pressure in the calibration coupler. Even if a large speaker or electromagnetic earphone is used, the output fluctuation can be minimized regardless of the cause of the fluctuation.
(6) In addition, the microphone for correcting the output of the acoustic calibrator is temperature-corrected by the technology of the present invention, and the entire system becomes “feedback-type output control using a microphone with temperature correction”, so an electret condenser microphone is used. In addition, the entire system can be configured at low cost and high stability can be provided.

(Condenser microphone unit)
(1) Considering the characteristics common to most condenser microphones, that is, among the changes in the surrounding environment, it is fairly stable against changes in humidity and pressure, but is vulnerable to changes in temperature. Since the change in sensitivity is corrected, stable characteristics can be obtained in any environment.
(2) Furthermore, regarding the individual microphones, variations in initial sensitivity and temperature gradient are not negligible, but the temporal reproducibility of their characteristics (trends) is high. Even an inexpensive electret condenser microphone can achieve stability exceeding that of an expensive condenser microphone.
(3) Rather, in the case of an electret condenser microphone that is mass-produced by an automatic machine (manufacturing robot), it cannot be adjusted by applying a large tension to the diaphragm in contrast to a condenser microphone that is manufactured through delicate adjustment for each unit. Therefore, this fact, on the other hand, shows the characteristic that the secular change is smaller than the former (even if the initial sensitivity and temperature gradient varies from individual to individual), and after applying the correction of the present invention focusing on this point Rather, the cheaper latter has the advantage that the characteristics are stable and high accuracy can be maintained.

(Sound level meter "acoustic measuring instrument")
(1) By adopting an electret condenser microphone that is inexpensive but has little secular change, it is possible to provide a noise meter that is less expensive than the prior art and that has high accuracy and high stability.
(2) A noise meter or measurement intended to reduce the lower limit of measurement based on the noise of the microphone itself and the background noise of the entire microphone unit (system) including preamplifier and head amplifier. By using the sensitivity correction method of the present invention, the background noise reduction correction can be stably applied at any temperature. In other words, a combination of both makes it possible to realize a sound level meter and an acoustic measuring instrument with extremely stable sensitivity capable of measuring to an ultra-low noise level.

(Sound calibrator)
(1) In general, the stability of a microphone is higher than the stability of a speaker, etc., so the output of a sounding body (speaker, electromagnetic earphone, etc.) by the output of a microphone = feedback control that controls the sound pressure is adopted as a system. The accuracy and stability of the calibrator can be greatly improved compared to the conventional one.
(2) In addition to this, when the above-mentioned temperature correction is applied to the microphone as a sound pressure sensor in the coupler section of the calibrator, the control accuracy is further improved, and even when an electret condenser microphone is used, it is inexpensive and has high performance. (3) Since the accuracy and stability of the calibrator is determined by the microphone, even if the output of the sounding body fluctuates for some reason, it can be reduced to the level of accuracy and stability of the microphone regardless of the reason. .

  As described above, in the present invention, if a temperature detection sensor is attached, and output correction means is applied to the preamplifier part of the microphone and integrated as a “condenser microphone unit with a correction function”, the initial sensitivity is an inexpensive microphone with a large temperature gradient ( An electret condenser microphone, etc.) can provide a very stable microphone unit. Whether to add the initial sensitivity correction means or to complete the correction at the manufacturing stage may be determined by the manufacturing stage procedure or the design specification.

  It can be used as a very stable acoustic sensor in measurements in high-temperature environments such as the vicinity of vehicles and blast furnaces, or in sub-freezing environments such as polar regions. Moreover, if a sound level meter is manufactured using this microphone unit, a highly stable product can be realized at a low cost.

  Furthermore, if it is used for an acoustic calibrator that controls the sensitivity of a sound level meter and the output of the speaker is controlled by the output, the accuracy of the output will be determined by the microphone unit with this correction function. A calibrator with high stability can be provided even if a sound generation unit (speaker) having large fluctuations is used.

(First embodiment “corresponding to first and second inventions”)
FIG. 1 shows a microphone unit 10 with a temperature correction function according to the first embodiment. The microphone unit 10 includes a cartridge unit 16 having a diaphragm 14 and a preamplifier unit 20 having an operational amplifier (OP amplifier) 18 in a cylindrical housing 12. In addition, the area | region where the diaphragm 14 in the housing | casing 12 is attached is made into the damping thick wall structure, and the device which does not have the trouble in the characteristic of the diaphragm 14 is made | formed.

  The casing 12 is made of metal, and the outer dimensions of the casing 12 are about 10 mm in diameter and 150 mm in length (when a 1/2 inch microphone is used). The diaphragm 14 is configured by facing a fixed electrode portion 14A and a vibrating electrode portion 14B.

  The fixed electrode portion 14 </ b> A is connected to the plus terminal of the bias power source 22, and the minus terminal of the bias power source 22 is connected to one connection terminal 24 with the preamplifier portion 20. The vibrating electrode portion 14B is connected to the one connection terminal 24 via a resistor R0. Thus, a positive charge is applied to the fixed electrode portion 14A and a negative charge is applied to the vibration electrode portion 14B by the bias voltage. The vibrating electrode portion 14B is connected to the other connection terminal 26 with the preamplifier portion 20 via a capacitor C1.

  The one connection terminal 24 is connected to the negative input terminal of the OP amplifier 18 via the capacitor C2 and the variable resistor R1, and is also connected to one terminal 28 for taking out an audio signal. The other connection terminal 26 is connected to the plus side input terminal of the OP amplifier 18.

  Further, the output terminal of the OP amplifier 18 is connected to the other terminal 30 for taking out an audio signal, and is connected to one input terminal of the OP amplifier 18 via a feedback resistor R2 for fastening the gain (amplification factor). ing. In addition to these basic configurations, a signal line from the thermistor 32 is connected to both ends of the feedback resistor R2. That is, the feedback resistor R2 and the thermistor 32 are connected in parallel.

  The thermistor 32 is attached to the outer periphery of the housing 12 and an end portion (side portion of the diaphragm 14) on the cartridge portion 16 side. The thermistor 32 constantly monitors the ambient temperature. That is, the thermistor 32 is configured such that the resistance value R3 changes according to the temperature change, and as a result, the resistance value of the feedback resistance element changes, the gain is adjusted, and the output level can be adjusted and controlled by the preamplifier unit 20. Has been. Since the resistance change with respect to the temperature change depends on the characteristics of the thermistor 32, it may be selected based on the gain change with respect to the temperature change of the applied microphone 10.

  FIG. 2 is a modification of FIG. 1 in which the thermistor 32 is provided inside the housing 12, and there is no functional change at all. Therefore, the other components are denoted by the same reference numerals as those in FIG. 1 and description of the components is omitted.

  The operation of the first embodiment will be described below. An outline of the operation of the microphone unit with temperature correction function 10 having the above configuration will be described.

  The initial sensitivity of the microphone unit 10 is previously adjusted by the variable resistor R1 so as to be within a specified sensitivity range at room temperature (20 ° C. to 25 ° C.). This adjustment may be performed at the manufacturing stage, or a pinhole may be provided in the housing 12 so that the resistance value of the variable resistor R1 can be adjusted and adjusted after shipment.

  When the ambient temperature increases, the resistance value R3 of the thermistor 32 connected in parallel to the feedback resistor R2 decreases. For this reason, automatic adjustment is performed so as to suppress an increase in sensitivity of the microphone unit 10 due to a temperature increase. On the other hand, when the temperature decreases, the resistance value R3 of the thermistor 32 increases and is automatically adjusted so as to suppress a decrease in sensitivity in the opposite direction.

  The degree of adjustment, that is, the temperature gradient is adjusted by the resistance R1 and the resistance value R3 of the thermistor 32. Depending on the characteristics of the diaphragm 14 of the cartridge unit 16, either the initial sensitivity or the temperature correction can be omitted.

  In this way, the output of the microphone unit 10 shows very stable sensitivity (output) with respect to changes in the surrounding environment, particularly temperature changes, and even when using an electret condenser microphone that is commercially available at a lower price than a condenser microphone, Expected to outperform an expensive measurement condenser microphone unit without correction. Rather, the electret type often does not apply tension to the diaphragm, and from this point of view, there are often fewer changes over time and changes over time than condenser microphones.

(Second Embodiment “Corresponding to Third Invention”)
The second embodiment will be described below.

  3 and 4 show the basic configuration of the microphone unit 10 described in the above first embodiment (because the thermistor 32 is not mounted, hereinafter referred to as a “microphone unit 10A”) of the sound level meter 50. It is an example applied as a part. Therefore, the description of the structure of the microphone unit 10A is omitted.

  As shown in FIG. 3, the sound level meter 50 has a structure in which a main control device is built in a rectangular box-shaped main body case 52, and a cylindrical sensor loop 54 protrudes from a part of the main body case 52. ing. The sensor probe 54 incorporates a micron unit 10A. The sound level meter 50 is not greatly changed in conventional appearance, size, weight and the like by adopting the technique of the present invention.

  As shown in FIG. 4, the microphone unit 10 </ b> A is connected to a frequency correction unit 58 via an A / D converter 56. The frequency correction unit 58 is connected to the temperature correction unit 60. Here, the thermistor 62 for detecting the environmental temperature is disposed in the vicinity of the microphone unit 10 </ b> A and is connected to the preamplifier unit 64. The preamplifier unit 64 is connected to the temperature correction calculation unit 60 via the A / D converter 66.

  A correction constant table memory 68 is connected to the temperature correction unit 60. For this reason, the output value from the frequency correction unit 58 is corrected by the temperature correction unit 60 according to the environmental temperature, and then the detection data is obtained via the logarithmic compression unit 70. The detection data is displayed on the display unit 72. This display is digitally displayed on the display unit 72.

  In the sound level meter 50 configured as described above, temperature correction constants are stored in advance in the temperature correction constant table memory 68 connected to the temperature correction calculation unit 60 in accordance with the initial sensitivity and temperature characteristics of the microphone. Then, a correction value is determined from the constant and the output of the thermistor 62 after A / D conversion. The corrected result is converted into a dB value by the logarithmic compression unit 70 and then displayed on the display unit 72. The logarithmic compression unit 70 may be a previous stage of the temperature correction calculation unit 60.

  For the sound level meter 50 or the like, the microphone unit 10 with the thermistor 32 described in the first embodiment (see FIG. 1 or FIG. 2) can be used as it is. Therefore, in the second embodiment, most processing is digitally processed and the whole is configured as a digital sound level meter. If temperature compensation is performed at the final stage as in the second embodiment, the sensitivity is stable with respect to temperature changes as well as variations in initial sensitivity, and the display reproducibility is excellent. can do.

(Third embodiment “corresponding to the fourth invention”)
A third embodiment will be described below. FIG. 5 shows the external appearance of the acoustic calibrator 100. The microphone unit 102A of the sound level meter 102 for measurement (hereinafter referred to as “measurement target 102”) is acoustically calibrated via the coupler unit 104. The main body 106 is connected.

  The sound level meter 102 (the assumed target 102) is a general sound level meter to which the thermistor 62 as shown in FIG. 4 is not added. Accordingly, the thermistor 32 (see FIG. 1 or FIG. 2) applied to the first embodiment does not exist in the microphone unit 102A, and the microphone unit has a basic configuration.

  As shown in FIG. 6, the coupler unit 104 is provided with a loading unit 108 into which the microphone unit 102 </ b> A can be loaded. The diaphragm of the microphone unit unit 102 </ b> A of the measurement target 102 loaded in the loading unit 108 (FIG. 6). (Not shown) is located in the inner space 110 of the coupler 104. In the space portion 110, a pair of sounding bodies 112 and a temperature correction target microphone 114 are disposed. The sounding body 112 can be an electrodynamic speaker, a piezoelectric speaker, an electromagnetic earphone, or the like.

  The sounding body 112 is connected to the output terminal of the AMP circuit 116 built in the acoustic calibrator body 106. An input terminal of the AMP circuit 116 is connected to the CPU 118. Therefore, the sound signal generated by the CPU 118 is amplified by the AMP circuit 116 and output from the sounding body 112. A temperature sensor (such as a thermistor) 120 is connected to the CPU 118, and an electrical signal based on the environmental temperature is input to the CPU 118. In addition, a correction constant table memory 122 is connected to the CPU 118.

  In the sound calibrator 100, the microphone 114 constantly monitors the output of the sounding body 112 while the sounding body 112 is sounding. The CPU 118 receives a signal from the microphone 114 or the temperature sensor 120 and amplifies the preamplifier or A / D converter, an oscillator or D / A converter that sends a calibration signal to the sound generator 112 via the AMP circuit 116, or It includes an arithmetic processing chip, a control circuit for the lighting lamp of the LED 124, and the like, and constitutes the core of the arithmetic processing. The acoustic calibrator 100 includes a battery unit 126 (which may be a stabilized power supply) including a power switch SW1.

  Hereinafter, the operation of the acoustic calibrator 100 will be described. When the power switch SW1 is turned on, the power supply voltage + Vcc is supplied from the battery of the battery unit 126 to each unit, and a calibration signal is output in the coupler unit 104 while the level is monitored and controlled. Here, two speakers are arranged as the sound generator 112 so that the sound field in the coupler unit 104 is sufficiently diffused and a stable sound pressure is obtained, but one speaker may be used in some cases.

  The output is constantly monitored by the microphone 114, and if there is a change in output, the output of the sounding body 112 is adjusted via the AMP circuit 116 and adjusted so as to have a prescribed sound pressure. When the ambient temperature changes, the temperature sensor 120 detects this, and the CPU 118 fetches data from the correction constant table memory and refers to it to correct the sensitivity of the microphone 114 to a specified value.

  As the data in the correction constant table memory 122, the initial sensitivity and the correction value (temperature gradient) for the temperature change are stored for each microphone 114 connected by the chain line X in FIG. As described above, the output from the sound generator 112, that is, the calibration sound pressure in the coupler unit 104 is always kept at the specified value. For this reason, the applied temperature compensation microphone 114 has initial sensitivity and temperature characteristics as long as the behavior (characteristics) with respect to the temperature is stable in time (if it has reproducibility). Even if there are variations, it is possible to construct a stable and high-performance acoustic calibrator even when a very inexpensive microphone such as an electret condenser microphone is used.

  Rather, the time stability of the sensitivity does not apply a large tension to the diaphragm like a general measurement condenser microphone, so the electret condenser microphone is often higher. It is advantageous. When the battery unit 126 as described above is used as the power supply voltage, the battery may be consumed and the power supply voltage + Vcc may exceed the allowable range. For this reason, an LED 124 for warning this is arranged on the outer surface of the main body, and at the same time, sound generation is stopped and double measures are taken so that calibration is not performed with an incorrect output.

1 is an internal configuration diagram of a microphone unit according to a first embodiment. It is an internal block diagram which shows the modification of the microphone unit which concerns on 1st Embodiment. It is a perspective view which shows the external appearance of the sound level meter which concerns on 2nd Embodiment. It is a circuit block diagram of the sound level meter which concerns on 2nd Embodiment. It is a perspective view which shows the external appearance of the acoustic calibrator which concerns on 3rd Embodiment. It is a circuit block diagram of the acoustic calibrator which concerns on 3rd Embodiment.

Explanation of symbols

R0 resistance R1 variable resistance (initial sensitivity correction means)
R2 feedback resistor (output correction means)
C1 Capacitor C2 Capacitor 10 Microphone unit 12 Housing 14 Diaphragm 14A Fixed electrode part 14B Vibration electrode part 16 Cartridge part 18 Operational amplifier (OP amplifier)
DESCRIPTION OF SYMBOLS 20 Preamplifier part 22 Bias power supply 24 One connection terminal 26 The other connection terminal 28 One terminal 30 The other terminal 32 Thermistor: R3 (temperature detection sensor, output correction means)
(Second Embodiment)
10A microphone orophone unit (basic configuration)
DESCRIPTION OF SYMBOLS 50 Sound level meter 52 Main body case 54 Sensor loop 56 A / D converter 58 Frequency correction part 60 Temperature correction part 62 Thermistor 64 Preamplifier part 66 A / D converter 68 Correction constant table memory 70 Logarithmic compression part 72 Display part (3rd Embodiment)
100 Sound calibrator 102 Object to be measured (Sound level meter)
102A Microphone unit section 104 Coupler section 106 Sound calibrator body 108 Loading section 110 Space section 112 Sound generator 114 Microphone (monitoring microphone)
116 AMP circuit 118 CPU
120 Temperature sensor 122 Correction constant table memory 124 LED
SW1 Power switch 126 Battery unit

Claims (8)

A microphone unit having a cartridge part having a diaphragm such as a diaphragm for converting sound, which is a pressure fluctuation wave, into an electric signal, and a preamplifier part for amplifying the electric signal obtained by the diaphragm,
An initial sensitivity correction means for correcting the initial sensitivity with respect to the amplification factor in the preamplifier unit with reference to a predetermined steady temperature;
A temperature detection sensor for detecting the temperature in the vicinity of the cartridge part or the preamplifier part;
Based on the output from the temperature detection sensor, output correction means for correcting the output from the preamplifier unit,
A microphone unit having It has a cartridge part provided with a diaphragm for converting sound, which is a pressure fluctuation wave, into an electric signal, and a preamplifier part for amplifying the electric signal obtained by the diaphragm, and at the time of manufacture, the amplification factor in the preamplifier part Is a microphone unit whose initial sensitivity is corrected with reference to a predetermined steady-state temperature,
A temperature detection sensor for detecting the temperature in the vicinity of the cartridge part or the preamplifier part;
Based on the output from the temperature detection sensor, output correction means for correcting the output from the preamplifier unit,
A microphone unit having   The microphone unit according to claim 1 or 2, wherein the microphone unit is configured as a condenser microphone or an electret condenser microphone.   The temperature sensor is a thermistor or a semiconductor temperature sensor, and the selection of the thermistor or the semiconductor temperature sensor depends on the correlation between the temperature characteristic of the thermistor and the temperature characteristic of the output of the preamplifier unit. The microphone unit according to any one of claims 1 to 3.   A noise meter for detecting noise, wherein the microphone unit according to any one of claims 1 to 4 is incorporated. A sound generator is built in, and an output monitoring microphone is arranged in the vicinity of the sound generator, and the output of the output monitoring microphone is constantly monitored and controlled to generate a constant calibration sound pressure. A microphone unit or a coupler unit for mounting an inspection target including a sound level meter, and an acoustic calibrator for calibrating the sensitivity of the inspection target.
A temperature detection sensor for detecting the temperature near the acoustic calibrator;
Output correction means for correcting the output monitoring microphone output based on the detection result of the temperature detection sensor;
An acoustic calibrator comprising:   7. A battery is used as a power source, and the battery further comprises warning means for warning when both the display means and sound generation are stopped when the battery is exhausted and the power supply voltage falls below an allowable range. Acoustic calibrator.   The temperature sensor is a thermistor or a semiconductor temperature sensor, and selection of the thermistor or the semiconductor temperature sensor depends on a correlation between a temperature characteristic of the thermistor and an output temperature characteristic of the monitoring microphone. The sound calibrator according to claim 6 or 7.

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