Microphone

A microphone has a microphone capsule, wherein the microphone includes a test arrangement, the test arrangement including an undervoltage detector, a test signal generator unit and an adder. The microphone capsule may be connected to the adder via a first electrical line, a supply voltage line being connected to the undervoltage detector via a second electrical line. In the undervoltage detector the operating DC voltage of the microphone may be comparable with an internal reference DC voltage, the undervoltage detector being electrically connected to the test signal generator unit, and the test signal generator unit may be electrically connected to the adder.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicant claims priority under 35 U.S.C. § 119 of German Application No. 10 2019 124 533.8 filed Sep. 12, 2019, the disclosure of which is incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a microphone.

2. Description of the Related Art

Especially for large events with several performance venues, it is necessary to provide large-scale monitoring of the sound levels across the entire venue.

For example, a microphone with an integrated sound level meter can be provided to measure these sound levels. This microphone can, for example, be a handheld device with an integrated display. However, such monitoring is very costly and personnel-intensive, because a handheld device is required for each measuring point and is therefore less suitable for large events.

In addition, sound level meters with detachable microphone and dedicated connection cable as well as measurement microphones with separate cable and dedicated measurement interface with a computer interface can be used for sound level measurements. However, with these two variants there is uncertainty with regard to the cable connections, since these can very quickly become defective. Possible manipulations cannot be avoided.

From DE 36 36 720 A1 a test device is known with which a method for functional testing of a microphone can be carried out. In this method, at least one loudspeaker is arranged at a fixed, preferably small, distance from the microphone and a test signal is applied to it, the signal frequency of which lies in the operating frequency range of the microphone. The phase difference between the microphone output signal and the test signal is measured, the measured phase difference being compared with a tolerance-prone target value and a good signal or a bad signal being output if the measured phase difference lies within or outside the tolerance range.

DE 10 2012 220 137 A1 describes a circuit arrangement for testing a dynamic microphone. The circuit arrangement comprises at least one test signal generation stage, through which the microphone can be subjected to an AC test voltage.

Finally, EP 0 589 974 A1 discloses a method for testing one or more capacitive converters by a central control unit, each converter being connected to an input of a preamplifier with a relatively high input resistance and a test line extending from the central control unit to the converters. The test of each converter is carried out with the help of a test signal which is transmitted via the test line. A capacitor with a small capacitance is provided in the test line for the connection between the converter and the input of the preamplifier, and by selecting the capacitance inserted in the test line with a very high equivalent parallel resistance or leakage resistance, which is large compared to the impedance of the capacitance. Frequency characteristic values, for example in the case of one or more discrete frequencies, are measured via the test line and the frequency characteristic values obtained are compared with previously determined characteristic values in order to identify errors which may occur in the converter. The test lead is connected to a changeover switch in the control unit, which is either connected to a housing or to an AC test voltage.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a microphone with which rapid, efficient and precise testing and diagnosis of the operating states of the microphone and of all downstream signal connection lines and signal processing devices is possible.

This object is achieved according to the features of the invention.

The invention thus relates to a microphone with a test arrangement for testing the microphone and external system components which are connected to the microphone. The microphone is preferably a measuring microphone for sound level monitoring. External system components are to be understood as all signal connection lines and signal processing devices connected downstream of the microphone.

The microphone has a microphone capsule and the test arrangement, the test arrangement containing an undervoltage detector, a test signal generator unit and a adder. The microphone capsule is connected to the adder via a first electrical line. A supply voltage line of the microphone capsule is connected to the undervoltage detector via a second electrical line, the direct voltage of the microphone being compared with an internal reference direct voltage in the undervoltage detector. The undervoltage detector is in turn electrically, preferably via an electrical line, connected to the test signal generator unit, the test signal generator unit being connected downstream of the undervoltage detector. The undervoltage detector can switch over the frequency of the test signal generator unit. Finally, the test signal generator unit is connected to the adder, preferably via an electrical line.

This test arrangement ensures quick, efficient and precise testing and diagnosis of the operating states of the microphone and all system components. For this purpose, the test arrangement generates a permanent, calibrated test signal that is fed in in addition to the microphone signal. The microphone signal generally covers the audible frequency spectrum (10 Hz to 20 kHz). The permanent calibrated test signal is in the range above twice the maximum signal frequency, so that the resulting intermodulation products are above 20 kHz and the actual microphone signal (microphone spectrum) is transmitted without feedback.

The test signal is preferably in the form of a sinusoidal signal with a calibrated amplitude and allows the suitability of the system components used to be assessed and signal-influencing changes to be recognized and detected by, for example, cables, attenuators, signal amplifiers, digitization with and without data compression, for example when using radio links to prevent such manipulation, since such manipulation is accompanied by a change in the amplitude of the test signal. To do this, however, it is necessary to first determine the transmission behaviour of the system at a lower frequency in the listening area compared to the permanent test signal frequency, because the frequency response of the system components usually drops towards higher frequencies.

The test arrangement also ensures that the correct power supply to the microphone is ensured. This is particularly important for event security, because sound level monitoring requires the correct measurement and transmission of high signal alternating voltages, sometimes up to over 20 Vpp, depending on the microphone sensitivity (see also DIN 15905-5, for example). For this purpose, the test arrangement has an undervoltage detector which, by switching over the generator frequency, causes a frequency jump of, for example, 10 kHz in the amplitude-calibrated test signal in a microphone. An undervoltage of a microphone can be clearly detected by the frequency jump of the permanent test signal. This undervoltage detector ensures that the microphone is provided with a sufficiently high supply voltage. A supply voltage that is too low prevents sufficiently high signal ac voltages corresponding to the sound level from being generated. In this case, the microphone can no longer reproduce the high sound pressure levels.

It is also advantageous that testing and diagnosis of the microphone and all downstream system components is possible solely with the test arrangement located in the microphone. External test devices are not required. Only software for diagnosis needs to be provided. It is furthermore advantageous that a suitable, calibrated test signal is made available to a user, on the basis of which it is possible to assess the suitability of the microphone and the system components used for transmitting high signal alternating voltages with correspondingly high sound levels.

With this test arrangement, it is possible to distinguish between several microphones at the event location on the basis of the frequency-coded test signal (microphone1: test signal frequency of 41 kHz; microphone2: test signal frequency of 42 kHz; microphone3: test signal frequency of 43 kHz, etc.) of the individual microphones. Hence, confusion of the microphones in the sound level measurement in audio networks is avoided.

In a preferred embodiment, the test signal generator unit of the microphone has a signal generator. An electronic switch can be used to switch between the reference test signal and the permanent test signal. This variant has a very compact design because the test signal generator unit consists only of the signal generator. The circuitry is also very low. However, reference AC test voltage and permanent AC test voltage must be evaluated one after the other.

In a further embodiment, the test signal generator unit has a test signal generator and a reference test signal generator, the reference test signal generator being switchable via a switch. The advantage here is that the reference AC test voltage and the permanent AC test voltage can be evaluated simultaneously.

In another embodiment, the test signal generator unit additionally has a noise generator, the noise generator being switchable via an electronic switch. The amplitude frequency response of external system components can be measured with this noise generator.

In a further preferred embodiment, the microphone has a first inverting output driver and a second non-inverting output driver, as a result of which the microphone has a symmetrical microphone output.

In another preferred embodiment, the evaluation and diagnosis of the function of the microphone and the downstream system components is carried out very quickly and easily by means of software from a computer.

Finally, the invention relates to a method for sound level monitoring. The process comprises the following successive steps:1. Exposing the microphone to an external acoustic sound pressure level at the level of the typical microphone sensitivity at 94 dB at a defined frequency (for example 1 kHz) or applying the microphone to a sound pressure level of 114 dB at a defined frequency (for example 1 kHz) and subsequent measurement the amplitude of the microphone output signal.2. Switch off or remove the acoustic test sound level and switch on the reference test signal (=actual reference test alternating voltage) at the maximum sound pressure level to be recorded (=upper limit of the alternating test voltage).3. Measurement of the amplitude of the reference test signal and check for plausibility of the measured amplitudes.4. Hook-up of the permanent test signal or switching the reference test signal to a permanent test signal.5. Comparison of the amplitude of the reference test signal with the amplitude of the permanent test signal, whereby a level difference is obtained, which corresponds to an amplitude correction factor.6. Monitoring of the permanent test signal in relation to the amplitude and frequency of each microphone.

It is advantageous in this method that different microphones can be distinguished on the basis of a production-specific, different test signal frequency (=frequency coding) of the permanent test signal within the test signal generator unit, so that several microphones with different test signal frequencies can work within a network of microphones in an audio network and are clearly identifiable.

By combining the test signal frequency and test signal amplitude, the operating states of each microphone, as well as the operating states of the signal chain, can be recorded and any manipulations can be analysed and verified.

It is also explicitly proposed to combine several features of the individual described embodiments with one another.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

InFIG. 1there is shown a schematic view of an arrangement1of power supply2and a first variant of a microphone3. The power supply unit2is part of an arrangement32of external system components, wherein further external system components are not shown.

The microphone3has a housing4in which a microphone capsule5and a test arrangement6are accommodated. The test arrangement6contains an undervoltage detector7, a test signal generator unit8and a adder9. The microphone capsule5is connected to the adder9via a first electrical line10, a coupling capacitor11being provided between the adder9and the microphone capsule5.

The supply voltage line33is connected to the undervoltage detector7via a second electrical line12,12′,12″, an operating voltage of the microphone3being compared with a reference voltage in the undervoltage detector7. The microphone3is supplied with energy via the supply voltage line33. The test signal generator unit8is connected to the undervoltage detector7, the test signal generator unit8being electrically connected to the adder9. The undervoltage detector7is preferably connected to the test signal generator unit8and the test signal generator unit8to the adder9via electrical lines13,14.

The microphone3is powered by phantom power from the external power supply2. For this purpose, a connecting line system15is provided, consisting of a ground line16, a first signal line17and a second signal line18. The phantom power supply itself is generated by the power supply unit2and supplied to the signal lines17and18via feed resistors19and20. Within the microphone3, the phantom voltage is coupled out via a diode resistor network21and22and fed to a voltage stabilization device23. This voltage stabilization device23supplies the microphone capsule5and thus the entire microphone3with energy.

The test signal generator unit8consists of only one signal generator30. The reference test signal can be switched to a permanent test signal by means of an electronic switch29.

The signal generator30provides a calibrated reference signal UR at a representative level of the maximum sound level to be detected and as a function of the microphone sensitivity UM, for example UM=94 dB, where: UR=UM+xdB. The reference test signal, preferably with a frequency in the range of the standardized acoustic calibration signal for sound level calibration (for example 94 dB at 1 kHz), is fed to the adder9.

The reference test signal is available together with an output signal US (microphone output signal US) coming from the microphone capsule5at the output of the adder9.

The undervoltage detector7is connected upstream of the signal generator30. This undervoltage detector7compares the supply voltage of the microphone3with the reference voltage at an input31.

If the operating voltage falls below the reference voltage, this is detected by the undervoltage detector7as an undervoltage, and the undervoltage detector7switches the signal generator30to a significantly lower permanent test signal frequency.

A microphone undervoltage can thus be reliably detected and transmitted to the evaluation software of a computer (not shown). Since the test signal generator unit8comprises only one switchable signal generator30, the test signal generator unit8has a compact design and the circuitry effort is very low. However, the reference test signal and the permanent test signal must be evaluated one after the other.

The output signal US coming from the microphone capsule5is applied to the input of the adder9in terms of AC voltage via the coupling capacitor11and is thus available for further signal processing by a subsequent output driver24.

The output of the output driver24drives the first signal line17of the microphone4via an impedance network25,26. The second impedance network27,28short-circuits the second signal line18in terms of AC voltage to the ground line16. The second signal line18is therefore only used for energy supply (economy circuit). In this embodiment, the internal signal processing is therefore asymmetrical.

The test arrangement guarantees that the correct power supply to the microphone is ensured.

This is particularly important for event security, because sound level monitoring requires the correct measurement and transmission of high signal alternating voltages, sometimes up to 20 Vpp, depending on the microphone sensitivity (see DIN 15905-5, for example).

For this purpose, the test arrangement has the undervoltage detector, which, by switching the generator frequency, causes a frequency jump of, for example, 10 kHz in the amplitude-calibrated test signal in a microphone. An undervoltage of a microphone can be clearly detected by the frequency jump of the permanent test signal.

FIG. 2depicts an arrangement46from the power supply2pursuant toFIG. 1and a second variant of a microphone40. The microphone40differs from the microphone according toFIG. 1only in that the microphone40has a test arrangement41, being constructed differently.

Most of the reference numbers have therefore been retained.

The test arrangement41in turn comprises the undervoltage detector7, the test signal generator unit8and the coupling capacitor11and the adder9connected downstream of the coupling capacitor11. However, the test signal generator unit8does not consist of only one signal generator. Rather, a sine reference test signal generator42is provided, which can be switched on via a switch43. The sine reference test signal generator42provides a calibrated reference test signal UR at a representative level of the maximum sound level to be recorded and as a function of the microphone sensitivity UM, where UR=UM+xdB (with UM being 94 dB, for example) applies. The calibrated reference test signal is also available in this variant together with the microphone signal US at the output of the adder9.

The reference test signal can be switched on and off manually or remotely via the electronic switch43. In addition to the reference test signal generator42, which can be switched on and off, the microphone40contains a permanent test signal generator44, the output voltage UP of which, unlike the reference test signal UR, has no effect on the microphone signal US.

The test signal generator44generates a test signal that is variable in frequency and has an amplitude that corresponds to the reference test signal UR. The test signal frequency fN is fixed according to the microphone coding. The test signal of a defined frequency fN and a defined amplitude UP=UR being generated is fed to the adder9and is available to the output driver24at the microphone output17, together with the microphone AC voltage US. The undervoltage detector7is connected upstream of the test signal generator44. This undervoltage detector7compares the operating voltage of the microphone40with its internal reference voltage at an input45. If the operating voltage falls below the reference voltage, this is detected as an undervoltage, and the undervoltage detector7switches the test signal generator44to a significantly lower frequency. A microphone undervoltage can thus be reliably detected and transmitted to the evaluation software of a computer (not shown).

FIG. 3depicts a third variant of a microphone50, which in turn is connected to the power supply2. Microphone50and power supply2form an arrangement51. The microphone50differs from those shown inFIG. 1andFIG. 2only in the structure of the test arrangement, which is why the reference numbers have been essentially retained.

For the sake of clarity, however, not all elements have been provided with reference numbers. The microphone50comprises a test arrangement52which has the undervoltage detector7, a test signal generator unit53, the coupling capacitor11and the downstream adder9.

The test signal generator unit52comprises a signal generator53and an electronic switch54with which the test signal can be switched between the reference test signal and the permanent test signal.

The signal generator53is in contact with the adder9.

In this respect, this arrangement51does not differ from that shown inFIG. 1. In addition, the test signal generator unit52includes an additional noise generator57, which can be connected via a control line55and an electronic switch56, for measuring and assessing the amplitude frequency response of the system components (not further shown), starting with the microphone output58up to software evaluation.

A remote control input59can also be seen, via which the noise generator signal of the noise generator57can be switched on or off.

FIG. 4depicts an arrangement60of the power supply2according toFIG. 1and a fourth variant of a microphone61. The microphone61comprises the test signal generator unit8according toFIG. 1.

The microphone61therefore differs only in that the microphone61has a second non-inverting output driver65in addition to a first inverting output driver62. An impedance network63,64connects to the inverting output driver62and an impedance network66,67connects to the non-inverting output driver65. Because of these two output drivers65,62, the microphone61has a symmetrical microphone output58. Hence, the signal coming from the adder9is simultaneously supplied to the non-inverting output driver65and the inverting output driver62. These output drivers62,65each have a gain of 0.5. From the non-inverting output driver65, the non-inverting output signal reaches the microphone output58via the output impedance66,67. Accordingly, the inverting output signal from the output driver62reaches the microphone output58via the output impedance63,64. If both output signals are evaluated by a corresponding system component, for example a computer sound interface with a differential input (not shown), the two individual microphone signals add up to 1.

The test signal and the reference test signal therefore appear at the microphone output58only with a single amplitude and not with a double amplitude.

FIG. 5depicts a further exemplary embodiment of the invention, a variant of a power supply unit70and a fifth variant of a microphone71forming an arrangement72. However, in this exemplary embodiment there is no phantom power, but constant current power instead. For this purpose, the power supply unit70has a constant current source73.

Therefore, the connection of the microphone71and the energy supply take place via only one electrical line, namely the line17.

Signal processing and power supply in the microphone71are almost identical to the variant according toFIG. 1, which is why the reference numbers of the individual components of the microphone71have been retained.

FIG. 6depicts a further arrangement80comprising a variant of a power supply unit81and a sixth variant of a microphone82. The microphone82comprises the test signal generator unit8according toFIG. 1. The microphone82is equipped with an integrated data chip (EEPROM) within a maintenance and data unit83, which can be easily read out via the existing microphone lines16,17,18or the connecting line system15, wherein these microphone lines also allow remote control and maintenance of the microphone82.

Maintenance and programming signals for maintenance of the microphone82are fed to the maintenance and data unit83via the identical microphone lines16,17,18. For this purpose, the maintenance and programming signals generated by an external computer are available to the maintenance and data unit83after a signal decoding in a diode network84. These maintenance and programming signals are expanded in the power supply unit81by means of a signal assignment via a relay switch85.

A phantom power is supplied via supply resistors19,20, which is switched off in the case of remote maintenance, a supply voltage86,87and a data line88then being connected.

In addition to the data line88, a signal line89and a ground line95can also be seen. By switching, the ground line95becomes the data line88.

FIG. 7depicts a device90comprising a microphone91, an analog-digital converter92and a computer93, the analog-digital converter92and the computer93being part of an arrangement94of external system components. The computer93or a software-integrated handheld device (not shown) is used to evaluate and diagnose the microphone function and other downstream signal components, such as the analog/digital converter92.

FIG. 8depicts a first variant of the device according toFIG. 7. This device100comprises a microphone101, an audio network converter102, an ethernet network103and a computer104. Audio network converter102and ethernet network103are part of an arrangement105of external system components102,103.

FIG. 9depicts a second variant of the device pursuant toFIG. 7. The device110comprises a microphone111and an arrangement112of external system components, namely an audio network converter118, two fiber optic converters113,114, which are connected to one another via a fiber optic cable117, and an ethernet network115.

The evaluation and diagnosis of the function of the microphone111and the downstream system components112to115,117is carried out with a computer116.

FIG. 10depicts a third variant120of the device shown inFIG. 7. The device120comprising a microphone121, an arrangement122of external system components123to125and a computer126.

The external system components123to125are a radio transmitter123and a radio receiver124, which are in contact with one another via radio. System component125is an ethernet network.

InFIG. 11depicts another variant130of the device shown inFIG. 7. This device130can be provided, for example, at a major event131with different event locations132,133,134. At each event location132,133,134, at least one microphone135to138, in particular a measurement microphone for sound level monitoring, is provided.

Each microphone135to138is connected to an audio network converter139to142, each of these audio network converters139to142being connected to an ethernet router143to145. The ethernet routers143to145are connected to an ethernet network149via ethernet cables146to148. The evaluation and diagnosis of the microphones135to138and the other downstream system components139to142and143to145takes place via a computer150, which is also connected to the ethernet network149.

FIG. 12shows a schematic representation of a microphone160, in particular a measuring microphone for sound level monitoring. In a housing161of the microphone160there is a printed circuit board162on which all components for microphone and system diagnosis are being arranged. In a rear section163of the microphone160, a connector164is provided, to which a cable can be connected, which is not shown inFIG. 12, however.

In a front section164there is a microphone capsule165, which is electrically connected to the circuit board162via a cable166.

The process for sound level monitoring comprises the following successive process steps (cf.FIG. 13, in which an amplitude curve is shown graphically at different frequencies):1. Exposing the microphone to an external acoustic sound pressure level181at a microphone sensitivity of 94 dB (reference number180) at a defined frequency, for example 1 kHz, or applying the microphone to a sound pressure level181of 114 dB (reference number180) at a defined frequency, for example 1 kHz, and then measuring the amplitude of the microphone output signal.2. Switch off or remove the acoustic test sound level and switch on the reference test signal183(=actual reference test alternating voltage183) at the maximum sound pressure level182to be recorded (=upper limit of the test alternating voltage), for example 140 dB (reference number182).3. Measurement of the amplitude of the reference test signal and check for plausibility of the measured amplitudes, the microphone sensitivity+xdB corresponding to the maximum sound pressure level181, in this case 94 dB+46 dB=140 dB. If the level of the reference test signal being measured by software is less than 140 dB, the system, which comprises one or more system components, cannot process the sound pressure level correctly. This means that one or more of the system components used are not suitable and may have to be replaced.4. Activation of the permanent test signal184(microphone according toFIG. 2) or switching from reference test signal183(=actual reference test alternating voltage183) to a permanent test signal184(microphones according toFIGS. 1, 3, 4, 5 and 6).5. Comparison of the amplitude A of the reference test signal183with the amplitude of the permanent test signal184; either directly when using two generators (reference numbers42,44; cf.FIG. 2) or after switching switch29(compareFIG. 1), whereby a level difference185is obtained, which corresponds to an amplitude correction factor185.6. Monitoring the permanent test signal184with respect to the amplitude A and the frequency of each microphone.

In the present example (cf.FIG. 13) the microphone1delivers a permanent test signal with a frequency of 41 kHz and is therefore sufficiently supplied with energy since the supply voltage is sufficiently high. If the test signal frequency were 31 kHz, the microphone1would not have a sufficient supply voltage. This too low supply voltage is detected as undervoltage within the microphone and the permanent test signal frequency is switched from 41 kHz (reference number184) to 31 kHz (reference number184′).

It is advantageous that different microphones can be distinguished on the basis of a frequency coding of the test signal within the test signal generator unit, so that several microphones (cf.FIG. 11; microphones135to138) can work with different test signal frequencies within a network.

A different test signal frequency (=frequency offset) is used for each microphone135to138, as a result of which each microphone can be identified on the basis of this test signal frequency (for example microphone135—41 kHz, microphone136—42 kHz, microphone137—43 kHz, microphone138—44 kHz).

Through the combination of frequency offset and amplitude measurement, the operating states of each microphone as well as the operating states of the signal chain can be detected and any manipulations, such as changing the gain of system components (microphone amplifiers), in particular reducing the gain and thus reducing the microphone signal amplitude, which means a reduction corresponds to the measured sound pressure level, or, for example, the insertion of signal attenuators can also be analysed and verified.

REFERENCE LIST