DE60012316T2 - PROGRAMMABLE MULTI-MODE, MULTI-MICROPHONE SYSTEM - Google Patents

Description

FIELD OF THE INVENTION

The The present invention relates to the fields of hearing aids and personal Amplification devices. In particular, the present invention relates to a programmable multi-microphone system for use with such devices that are capable of to work in different modes or operating modes.

BACKGROUND OF THE INVENTION

A key component any hearing aid or another, personal reinforcing device is the microphone system that receives and receives acoustic signals into electrical signals for processing in the hearing aid or the device converts. A microphone has a responsiveness that is either directional, i. depending on the direction of the sound incidence, or omnidirectional, i. regardless of the direction of the sound incidence. One directional responsiveness can be loud for a user listening environments be beneficial where the user is particular or alone from the sound affected by a specific source. In such make is the desired one Signal usually a source in front of the carrier or the user of the hearing aid lies, and the sounds are typically competitive speakers or background conversations that from the sides or the back go out of the speaker. Because the user has a larger signal to noise ratio (SNR) requires to understand a language as a person with one normal hearing, is a directional response that dampens sounds coming from the side or the back go out of the user, advantageous. Conversely, in quiet surroundings an omnidirectional microphone system is often desirable.

One omnidirectional microphone usually has a single inlet tube, where an air pressure is transformed into a voltage. A directionality in one single microphone can be by enclosing both inlets before as well as behind a diaphragm in the microphone and by adding a acoustic resistance over a hole can be reached in the rear inlet. It is also known a front and back pair of omnidirectional microphones to use to form a directional microphone system. In Such a multi-microphone system will be the difference between the output the front microphone and an electronically delayed version the output of the rear microphone typically used. The Form of the directional response of such a system is, among other parameters, of the value of the electronic Delay of the Signal of the rear microphone and the distance that the inlets of the two microphones separated from each other, hang. By varying this Parameter, the response can be different, cardioidale Take forms.

To the Example discloses United States Patent No. 5,757,933 to Preves et al. a device comprising a first and a second non-directional (or omnidirectional) microphone and a switching mechanism, to allow a user between a non-directional mode in which only a first Microphone output is enabled, and a directional mode, in both microphone outputs be used to switch. In directional mode can they Phase and the amplitude of the inverted, second microphone output be adjusted so that the manufacturer of the hearing aid the pattern of the directional Response between a cardioid pattern and a "super" or modified, cardioid pattern as desired by a hearing impaired user, can vary. Settings can also be made to differences in the manufacturing tolerances between the first and the second microphone to compensate.

Indeed are many hearing aids Provided that they have a fixed directionality response show, and so there can be no requirement, the cardioidale Shape of the directional response of a microphone system according to the preferences of a user, as described by Preves et al. is made. In contrast, what is lacking in the prior art is a system that allows a manufacturer to automatically a directional Responsiveness for any given distance between omnidirectional microphones to accomplish. This distance can be considerably different Devices vary, for example, from behind the ear (behind-the-ear - BTE) to to hearing aids in the ear (in-the-ear - ITE). The system of Preves et al. is related to the use limited with the ITE hearing aid. Farther requires the ability the phase delay and the reinforcement in the system of Preves et al. to set, even a manual Setting of variable circuit components.

In addition, in a directional multi-microphone system, the microphones should be adjusted for both sensitivity (or gain) and phase. Similar models of component microphones may differ unacceptably in terms of sensitivity. While Preves et al. to make adjustments to compensate for differences in manufacturing tolerances, neither a way of automatically nor optionally making it is proposed to achieve a specific, directional response. Manual adjustments are made only in response to the reaction of the individual user impaired in hearing, which is a time consuming and laborious process.

directional Microphone systems also suffer from a low frequency (bass) loss of acoustic inputs especially when the distance between omnidirectional microphones is small such as in an ITE hearing aid. Because of this inherent, acoustic filtering transmits the system lower, acoustic frequencies less strong than higher, acoustic ones Frequencies and results in a reduced signal-to-noise (SNR) ratio. Around To counter this problem are circuits for low frequency emphasis or equalization has been incorporated into directional microphone systems. However, reinforced, in providing a gain in relation to the muted Low frequency components, such an equalization circuit the internal noise energy of the microphones in the system. In some carriers of this hearing aid does this often to unpleasantly high noise levels. However, in systems According to the prior art, which is to operate in both a directional Mode as well as an omnidirectional mode are suitable, both operating modes are affected by the reduced SNR, which is due to the inclusion of a Low frequency equalization circuit results. This is problematic because of a low frequency loss Of acoustic information in general no problem in omnidirectional Systems is.

Finally, allow Although many microphone systems of hearing aids switch between one Microphone input and a telecoil input allow, and although some Systems also have a combined or mixed microphone and telecoil input provide prior art systems not to a user, the extent of input mixing according to possible listening preferences in environments with a different sound pattern.

The EP-A-0 499 699 discloses a hearing aid which a microphone with 2 omnidirectional microphones has. Each one is used to provide an omnidirectional characteristic and both are used simultaneously to be a directional one To get characteristic. The problem of microphone mismatch will not turn to you.

SUMMARY OF THE INVENTION

According to one In the first aspect, the present invention provides a microphone system, comprising: (a) a first omnidirectional microphone for receiving an acoustic signal and generating an electrical signal dependent on from that; (b) a second omnidirectional microphone for receiving of the acoustic signal and generating a second electrical Signals in dependence of which, with the first and second microphone near a surface a housing for the Microphone system are located and by a certain distance at this casing are separated; (c) a programmable amplifier circuit compatible with the first and second microphone is coupled to an adjustable delayed version to generate the second electrical signal and adjustable the Sensitivity of the first microphone with the sensitivity of the second Microphones in accordance bring to; and (d) switching means associated with the programmable Circuit is coupled to optionally a first mode signal and / or to generate a second mode signal at a node, wherein the first mode signal is a sum of the first electrical signal Contains the signal and the second electrical signal and the second mode signal is a sum of the first electrical signal and the delayed Version of the second electrical signal contains.

Preferably the microphone system further includes: (e) a programmable Low frequency equalization circuit with an input connected to the Input node is connected, and an output to provide an output signal that is a programmable, variable variable Low frequency equalization. Also preferably represents the Equalization circuit ready the output signal without low frequency equalization, when the first mode signal is provided at the node and the equalization circuit outputs the output signal desired Size of a low-frequency equalization when the second mode signal is generated at the node becomes.

In one embodiment, the programmable circuit comprises: (a) a first programmable resistor connected between the first omnidirectional microphone and the node; (b) a series combination of a delay stage and a second programmable resistor, the series combination being connected between the second omnidirectional microphone and the node and the delay stage including a third programmable resistor; (c) an invariable resistor connected between the second omnidirectional microphone and the node. In another aspect, the present invention provides a method of calibrating this embodiment of the microphone system, comprising the steps of: (a) adjusting the first programmable resistor such that the sensitivity of the first microphone is the sensitivity of the second microphone matches when the first mode signal is provided at the node; (b) adjusting the second programmable resistor such that the sensitivity of the first microphone matches the sensitivity of the second microphone when the second mode signal is provided at the node; (c) adjusting the third programmable resistor so that when the second mode signal is provided at the node, the second mode signal produces a desired directional response with respect to the acoustic signal for any value of the distance between the first and second omnidirectional microphones.

Further Objects and advantages of the invention will become apparent from the following Description will be apparent, together with the accompanying drawings is made.

SHORT DESCRIPTION THE DRAWINGS

In the drawings, which, by way of example, preferred embodiments represent the invention:

1 Fig. 10 illustrates a prior art directional microphone system using two omnidirectional microphones;

2 represents the cardioidic form of a directional response of a microphone system;

3 Fig. 10 illustrates a first embodiment of the multi-microphone system according to the present invention;

4 Fig. 12 illustrates another embodiment of the multi-microphone system according to the present invention;

5 Fig. 12 illustrates the calibration setting for the multi-microphone system of the present invention; and

6 - 8th illustrate various stages in the calibration process for the multi-microphone system.

DETAILED DESCRIPTION THE INVENTION

An omnidirectional microphone has a response that is independent of the direction of the incoming sound. 1 represents a well-known microphone system 10 The two omnidirectional microphones 12 and 14 used to get an overall directional response, with sounds coming from the sides 36 or the back 38 of the system 10 emanating, in comparison to muffled sounds coming from the front 40 of the system 10 come from. The signals 36 . 38 and 40 are components of the entire acoustic signal received by the system 10 , As 1 shows owns each omnidirectional microphone 12 and 14 an inlet pipe 16 and 18 each, at the air pressure in an electrical signal 22 and 24 each transformed. The inlet pipes 16 and 18 are in openings in a surface or front panel 20 a housing (not shown) of the system 10 arranged. The inlet pipes 16 and 18 , and therefore the microphones effectively 12 and 14 , are separated by a distance d. In the system of 1 can the microphone 14 be referred to as the front microphone and the microphone 12 can be referred to as the rear microphone.

In a known manner, the electronic delay circuit takes 26 the signal 22 on and gives a delayed signal 28 whose difference from the signal 24 at 30 is obtained, an output signal 32 of the microphone system. The output signal 32 indicates a directional response with respect to the acoustic input received 16 and 18 , The signal 32 subsequently becomes an amplifying device 32 supplied, such as a hearing aid signal processing unit, in a common housing with the microphone system 10 can be arranged.

The directional response of the signal 32 as a function of the angle of incidence θ in the horizontal plane, measured from the axis of directionality 42 at the front of the system 10 out (like this in 1 is shown), is generally, in polar coordinates, given by D (θ) = kd (β + cos θ) where d is the distance between the microphones 12 and 14 k is a constant and β is the ratio of the electronic delay in the block 26 to the external delay between the microphones is. The external delay between the microphones 12 and 14 is effectively the distance d divided by the speed of sound in air (344 m / s). Therefore, the directional response D is a function of both the internal electronic delay in the block 26 as well as the distance d, with which the microphones 12 and 14 separates each other. (In practice, the directional response D will also depend on the frequency of the acoustic signal components as well as the angle of incidence of such components in the vertical plane).

The form of the directional response In the case of β = 1, the external delay corresponds to the internal electronic delay, and the response is purely cardioidic as in 2 is shown. Different directional responses can be obtained by decreasing the value of β such that the internal electronic delay is less than the external delay. Generally, as β is reduced, the directional response becomes super-cardioidic, with sounds emanating from the sides being further attenuated and sounds emanating from the back experiencing lower attenuation compared to the cardioidic response in FIG 2 , This effect continues until a hypercardioid response at β = 0.33 is achieved. Further decreases result in a bidirectional response (or "similar to the figure of 8") that is relatively uniformly sensitive to sound arriving from the front and rear, and insensitive to sound arriving from the sides β increases the cardioid shape of the response and eventually leads to an omnidirectional response For most, directional applications of a hearing aid, β would normally be varied from 0.33 to 1.0.

typically, will be a specific microphone layout (comprising a fixed Microphone separation d) together with a suitable, internal, electronic delay selected to the desired β or the to obtain directional response. Therefore, in, must many prior art systems, both the separation d) as well as the electronic delay have been previously established be the desired one Achieve responsiveness. The present invention provides a microphone system that allows that a desired, directional response for any range of microphone separation distances so that the microphone system, for example, in conjunction with housings for both ITE hearing aids as well as BTE hearing aids can be.

3 shows a first embodiment of a microphone system 50 according to the present invention. As in 3 has been shown, the microphone system 50 suitably monolithic as an integrated circuit 52 with pins 54 . 56 . 58 . 60 . 62 . 64 . 66 . 68 . 70 . 72 . 74 . 76 . 78 , and 80 be formed.

As 3 shows, an electrical signal from a first or front, omnidirectional microphone to a pen 56 and the electrical signal from a second or rear omnidirectional microphone becomes a pin 54 fed. The signals at the pins 54 and 56 can the signals 22 and 24 each in 1 be. The electrical microphone signals are preferably included 84 and 86 each buffered to isolate the effect of switching between different modes in the subsequent stages. The buffers 84 and 86 act to invert the microphone signals and can also pre-amplify the signals. A power supply signal VB becomes the integrated circuit 52 at the pin 64 fed while a regulating tension on pins 60 and 62 to an on-chip regulator 82 is supplied to support the microphone components against power supply fluctuations. The pencils 74 and 76 are grounded, as is in 3 is shown to be a reference voltage to the system 50 in a known manner.

A Telecoil option is on the pins 66 . 68 and 70 intended. A telecoil (not shown) is an external component that facilitates hearing by an impaired listener with a hearing aid on a telephone or in a looped area to suppress the interference of background noise. A looped area basically comprises a wire or cable installed in the form of a loop around the perimeter of the area. The cable is connected to an amplifier and to one or more sound sources. When an electric current passes through the wire, an electromagnetic field is generated within the loop and this is picked up by the telecoil or telecoil. As in 3 is set, a Telecoil input Tin on the pin 66 at the stage 90 strengthened. The output of the amplifier 90 Tout becomes the pen 68 for applications that require a switch option of an external telecoil. A reference voltage Tref for the Telecoil component also becomes the stylus 70 through the stage 92 fed.

As before 3 shows, the buffered signal of the rear microphone via a resistor R5 and a programmable switch SW2 along a first path to a node 96 switched. The buffered signal of the rear microphone is also switchable via a programmable resistor PR2, a delay stage 89 , a programmable resistor PR5 and a programmable switch SW3 along a second path to the node 96 fed. As in 3 is shown, the delay stage 89 an amplifier 88 which, as a feedback, has a programmable resistor PR4 in parallel with a capacitor C5. The delay stage also provides the necessary inversion to provide directional response, ie, the difference between the front microphone signal and the delayed rear microphone signal. The Telecoil output signal Tout (which the ampl te Tin Signal) is also switchable via a programmable resistor PR1 and a programmable switch SW4 to the node 96 fed.

All signals at the summing node 96 are added together to form an input for the low frequency equalization circuit 95 to obtain. As in 3 is shown, the equalization circuit 95 an amplifier 94 comprising a feedback circuit consisting of a resistor R7 in series with the parallel combination of a capacitor C6 and a programmable resistor PR6. The output of the microphone system 50 will be at the pin 72 and this signal may be supplied to a subsequent signal processing circuit (not shown) in the hearing aid or amplification device. The equalization stage 95 Optionally, an amplification of the signal at the node 96 deliver.

As explained below, the programmable microphone system provides 50 In accordance with the present invention, a wearer of a hearing aid or a user of a booster with a number of possible different modes of operation is suitable. Furthermore, according to the present invention, eliminates the programmable system 50 in conjunction with a calibration software running on a computer, with a sound card and a speaker, various disadvantages found in prior art systems.

Programmable and automatic adjustment of the programmable resistor PR4 with the calibration software allows the system to operate 50 provide a very wide variety of directional responses for virtually any microphone port spacing. This gives a manufacturer the flexibility, the multi-microphone system 50 in different package types and sizes - making it suitable for BTE hearing aids, ITE hearing aids, or other sized devices - greatly increasing the manufacturer's passive device rate. As a result, a manufacturer can automatically achieve optimum directional response for any given distance between omnidirectional microphones. The specifically selected directional response may be selected in advance by a manufacturer, or may be adjusted during a "customization" process operation for a particular individual.

The omnidirectional microphones also need to be adjusted in terms of sensitivity (gain) and phase for a directional microphone system to be effective. In most cases, microphones designed for hearing aid applications are sufficiently phase matched, so this is not a problem (any mismatch in the phase of the omnidirectional microphone pairs may also occur during adjustment of PR4 in the phase delay circuit 89 be compensated). On the other hand, microphones from different production batches can vary greatly in sensitivity, often up to ± 3 dB. The degree of attenuation achieved near the zero crossings of a directional response is adversely affected if the sensitivities of the microphones are not matched. While some microphone manufacturers often offer the option of customized microphone pairs, a premium for this service will still be charged. In addition, even a matched pair of microphones sold by a manufacturer can be matched only within a certain range (eg, 1 dB), which can often be sufficient enough to affect directional response. The microphone system 50 includes programmable resistors PR3 and PR5 in the phase delayed path of the rear microphone signal (from the pin 54 ) and a programmable resistor PR2 in the path of the front microphone signal (from the pin 56 ). The programmable resistors, which are under the control of the calibration software, allow for gain-trimming the output of the rear microphone to compensate for any mismatch between the sensitivities of the microphones. When two programmable resistors PR3 and PR5 in the backward delay path in the illustrated embodiment of FIG 3 It would also be possible to use a single, programmable resistor in this path. However, the embodiment of the 3 preferred because it allows a better adaptation of the sensitivity, for example less than 0.1 dB, can be achieved. Such accurate matching would be achievable with only a single, programmable resistor in the delay path. In addition, inclusion of a programmable gain resistor PR2 in the path of the front microphone is required, as will be explained below, for adapting sensitivity in a two-microphone omnidirectional mode.

As a result, the multi-microphone system allows 50 In accordance with the present invention, the hearing aid manufacturer may use an unmatched pair of microphones, thus eliminating additional costs associated with acquiring matched pairs, and generally providing better matching than that achieved by a manufacturer , Furthermore, in the event that a microphone fails, only the faulty microphone must be replaced because the program adjustable gain resistors (PR2, PR3 and PR5) can be readjusted by the calibration software to compensate for any mismatch in sensitivity between the new and the original microphone.

As previously mentioned is, transfers, due to inherent, acoustic low-pass filtering (low-cut filtering), a directional microphone system lower, acoustic Frequencies, less strong than higher ones acoustic frequencies and results in a reduced signal-to-noise (SNR) ratio. This Low frequency or bass loss is then amplified when the distance between omnidirectional microphones is low, such as in an ITE hearing aid. A circuit for emphasizing a low frequency or an equalization circuit, used to counter this problem provides reinforcement in terms of on the muted Low frequency components, increased but at the same time the internal noise energy in the microphones. In many cases this leads to unacceptably high noise levels for the user of the hearing aid or Amplifying device.

The present invention minimizes this problem by increasing the degree of equalization in the stage 95 is made variable. As in 3 can be achieved by adjusting a programmable resistor PR6. As a result, a tradeoff can be made between compensating for acoustic information loss in the low frequency range and a noise level still acceptable to a user. In this way, a manufacturer or distributor can achieve a certain amount of low frequency amplification at a reasonable cost of amplifying the internal noise level in the microphones. Alternatively, the system can 50 be pre-programmed to achieve different levels of equalization in different modes, as explained below. For example, a directional mode with a substantial amount of low frequency equalization and a directional mode with only a small amount of equalization could be preprogrammed separately in the system, allowing a user or carrier to choose between these options as desired. In addition, for modes that provide omnidirectional response to an acoustic input, the equalization circuit 95 can be programmably configured to achieve low frequency equalization (ie no low frequency amplification), since loss of low frequency in such modes is not a problem. As in 3 can be seen, the stage can 95 be programmed so as not to achieve equalization by reducing the resistance across PR6 to zero, effectively short-circuiting it.

In many cases can a user of a hearing aid also wish switch between a microphone input and an available telecoil input or to mix a telecoil input with a microphone input. The microphone system of the present invention further enables that strength the Telecoil input is mixed with a microphone input so around according to the different preferences by means of a programmable Resistor PR1 to be varied. Again, such programming selections by a manufacturer or distributor during a calibration or adaptation process as well as by a user of a system, in the at least two modes or modes with different circumferences a telecoil input mix has been programmed become.

As a result, the present invention provides a multi-microphone system that is capable of operating in multiple, different modes. Preferably, the system provides 50 a user with at least one directional mode with two microphones and one omnidirectional mode with two microphones. In the directional mode with two microphones, the programmable switches SW1 and SW3 are closed and the programmable switch SW2 is open. In the two-microphone omnidirectional mode, the programmable switches SW1 and SW2 are closed and the programmable switch SW3 is open. In this mode, adjustment of the sensitivity between the front and the rear microphone is achieved by programmably setting PR2 with the calibration software (no adjustment in the back path occurs because R5 is a fixed resistor) so that the signals from each microphone that at the node 96 arrive, are correlated. Because these signals correlate. whose sum results in a signal level of 6 dB, twice the original signal level in each microphone. However, the internal noise energy in each microphone is uncorrelated, and therefore the accumulated signal at the node results 96 to an increase in the noise level of only 3 dB (√ 2 times the internal noise energy in each microphone). As a result, the omnidirectional mode with two microphones with a sensitivity adjustment achieves an increase of 3 dB in the SNR. If desired, in this mode, the total output can be attenuated by 6 dB by adjusting the programmable resistor PR2 (with a suitably selected value for the fixed resistor R5), so that the effective result is a reduction of 3 dB is in the level of noise power of the microphone relative to a single, omnidirectional microphone.

In addition, the microphone system 50 Programmable can also be configured to achieve numerous other possible operating modes or operating modes. The system can achieve an omnidirectional mode for a single microphone in which only the signal from the front microphone (on the pin 56 ), by closing SW1 and opening SW2 and SW3, or the signal from the rear microphone (on the pin 54 ) by closing SW2 and opening SW1 and SW3 to the node 96 is supplied. These two modes may be useful, for example, when either the front or the rear microphone fails, or when the battery power is low (and thus can be saved by operating in the lower power mode where only the working microphone is powered). In one embodiment of the invention, one of these modes may be entered automatically if a controller or processor in a digital hearing aid or amplification device determines that a microphone failure has occurred or the battery power of the device is low.

By adding selective amounts of low frequency equalization in the stage 95 in the directional mode with two microphones the system creates 50 furthermore numerous, different modes of a directional operation. The equalization provided is determined by a programmable resistor PR6 described above. It will be recalled that there is generally no need to provide equalization in an omnidirectional mode, however, as previously indicated, the step may be 95 be used in an omnidirectional mode to achieve amplification.

The multi-microphone system 50 also creates a basic telecoil mode by closing SW4 and opening SW1, SW2 and SW3. In any of the non-telecoil modes described above, the telecoil input may also be input to the front and / or rear microphone inputs (pins 56 and or 54 ) by closing SW4 in addition to the other required switch settings for the mode. Finally, by adding only selectively attenuated sizes of the telecoil input, numerous other variants of each mixed microphone telecoil mode are possible. The attenuation of the telecoil input is determined by the programmable resistor PR1. It should be noted that when no mixing of the telecoil input occurs, the switch SW4 remains open in this mode.

Setting each of the programmable resistors and each of the programmable switches of the system 50 for any of the modes indicated above may be stored in a non-volatile memory provided by the microphone system 50 is accessible. The non-volatile memory may be a specific memory belonging to the system 50 or may be part of a larger memory used by the hearing aid or amplification device.

In 3 creates the pen 78 a memory or memory or mode selection provided with an external switch (not shown) for selecting between different ones of these preprogrammed modes for operating a multi-microphone system 50 connected is. The external switch may include a pushbutton, toggle switch, or other type of switch positioned so as to be easily accessible by a user of the hearing aid or device (for example, to the housing thereof). The switch allows a user to quickly switch between preprogrammed modes of operation. In each mode are the settings for the pre-programmable resistors and the pre-programmable switches of the microphone system 50 set and stored in a memory. The system may include any number of preprogrammed modes, and, in a preferred embodiment, the system comprises 50 sufficient memory for the programmable settings of at least four different operating modes that can be stored. Preferably, at least the directional microphone mode and the omnidirectional microphone mode are preprogrammed among the modes in the memory, with additional pre-programmed modes selected by a manufacturer, distributor or user.

In an alternative embodiment can the Telecoil input and Telecoil mixing modes through a separate switch be controlled to a mixing of the Telecoil input in any the pre-programmed microphone modes easier.

Likewise delivers in 3 the pencil 80 a serial, digital communication interface for communication between the microphone system 50 (ie the chip 52 ) and a programmable microprocessor (not shown). The processor typically controls operation of the entire hearing aid or device amplification system and is housed within such a system. The microprocessor sends over the pin 80 serial, digital information representing the programmable resistors and the programmable switches of the microphone system 50 according to a certain preprogrammed operating mode, or as during the calibration / adjustment steps of the microphone system 50 is required (described below), adjusts.

It should be noted that the programmable switches SW1, SW3 and SW4 in the system 50 conventionally may be performed by respectively using programmable resistors PR2, PR5 and PR1, which include an open circuit (infinite resistance) setting such as the programmable resistors in the integrated circuit ER102 made by Etymotic Research.

It will also be apparent to those skilled in the art that, at the lag stage 89 , a fixed resistor can be used instead of PR4, and a programmable adjustable capacitor can be used instead of C5 without the operation of the system 50 in 3 to influence. A similar change could be made with respect to PR6 and C6 in the equalization stage 95 in 3 be made.

4 represents another embodiment of the multi-microphone system 50 the present invention with two changes compared to the embodiment of 3 First, the delay stage 89 ' in 4 has been modified as shown with two additional fixed resistors R9 and R10. In addition, the programmable resistor PR4 has been omitted, the setting of the programmable resistor PR3 now being limited by the amount of delay in the stage 89 ' is controlled. The delay level 89 ' effectively provides overall pass-through response, as opposed to the delay stage 89 in 3 , which provides a low pass response. Otherwise, the delay stages work 89 and 89 ' similar. Also, since the delay level 89 ' in 4 does not provide inversion of the delayed signal of the rear microphone, the inverting buffer in the path of the front microphone ( 84 in 3 ) not in the embodiment of 4 required. The inverting buffer 86 provides the necessary inversion in the delay path for the signal of the rear microphone in 4 , Non-inverting buffers (not shown) could be included in the paths of the front and rear microphones, but these are not necessary.

Furthermore possesses, in 4 , the programmable resistor PR2 has a set resistance Rs in series and a set resistance Rp in parallel therewith. This series-parallel combination achieves higher precision during amplification trim steps when PR2 is adjusted. This alternative is particularly suitable where a large portion of the available range of PR2 would otherwise not be utilized during a gain trim.

As mentioned earlier, the programmable multi-microphone system is initially calibrated to automatically trim out any sensitivity mismatches between the front and rear microphone (for the operating modes of the two microphones) and to automatically adjust the time delay (or phase delay) of the stage 89 to be adjusted to provide a desired directional response for any microphone port spacing. The calibration setting is in 5 for a multi-microphone system 50 with a front, omnidirectional microphone 102 and a rear, omnidirectional microphone 104 shown.

As in 5 is illustrated, the calibration setting includes a computer 110 having a calibration software according to the present invention running on it. The computer 110 includes a sound card 112 , a speaker 114 and an A / D converter card 116 , As will be understood by those skilled in the art, the sound card allows 112 that the computer 110 a sound over the circuit board of the speaker 114 outputs. Also, as in 5 is specified, the speaker 114 be positioned at two different positions relative to the hearing aid (or equivalently, the hearing aid may be positioned at two different positions relative to the position of the fixed loudspeaker). In a first position, shown at 114-1 , the speaker is positioned so that the acoustic signal emanating from the speaker is any microphone 102 and 104 reached at the same time with the same intensity. In a second position, shown at 114-2 , the speaker is positioned so that the acoustic signal emanating from the speaker is the rear microphone 104 reached before it's the front microphone 102 reached. The output of the microphone system is from the stylus 72 out, with the computer via an A / D converter card 116 connected to achieve a digital version of the microphone output signal in a known manner.

It is alternatively possible to use the microphone system 50 to calibrate after being integrated with a hearing aid or amplification device. In this case, the computer can 110 have a microphone (not shown) attached thereto so as to measure the acoustic output of the hearing aid or the amplifying device during the calibration process (instead of the computer measurement of the output of the electric microphone system).

The calibration procedure for calibrating the multi-microphone system of the present invention is generally divided into three major stages, as shown in FIGS 6 . 7 and 8th is shown. 6 represents the first stage in which a sensation adjustment for omnidirectional mode with two microphones by performing the steps 150 - 164 can be achieved. As 6 shows, this level requires the calibration setting to be as with 114-1 in 5 is shown, so the microphones 102 and 104 an output from the speaker 114 received at the same time and with the same intensity. The programmable switches SW3 and SW4 remain open through this stage. With SW2 closed and SW1 open, a test sound is generated by the computer and the resulting output of the microphone system is measured. This measurement is first on the rear microphone 104 because, in this mode, the fixed resistor R5 is present in the signal path of the rear microphone. Next is the measurement for the front microphone 102 repeated, ie with SW1 closed and SW2 open. The PR2 setting is adjusted until the measured level for the front microphone 102 best the measured level for the rear microphone 104 adapts.

7 represents a second calibration stage, in which the appropriate phase delay in the delay stage 89 ( 3 ) by performing the steps 180 - 204 is set. In the step 180 the setting is arranged so that the rear microphone 104 the acoustic output from the speaker 114 in front of the front microphone 102 receives, for example, in the setting 114-2 in 5 , In the steps 182 - 190 The effective distance between the front and rear microphone is measured. This is done by turning SW1 and SW2 on and off in a complementary manner (with SW3 and SW4 open), so that the output of the microphone includes components of the signal received by each microphone. The phase difference of these components is calculated, converted to a time value and subsequently to an effective distance (d) for microphone spacing. From this value of d and the desired directional response, ie, β, becomes a target time delay for the delay stage 89 calculated (step 192 ). Next, with SW1 and SW4 open, a similar complementary switch is made to SW2 and SW3 to go back to step 200 to obtain a phase difference between the direct path of the rear microphone and the delayed path of the rear microphone. This phase difference becomes the effective time delay in the stage 89 transformed. The setting of PR4 (in the embodiment of FIG 3 ) is then adjusted until the effective time delay next adapts the target time delay.

The third calibration level, shown in the steps 210 - 224 in 8th achieves sensitivity matching in the directional mode with two microphones. The steps of 8th are similar to the calibration steps of 6 with the exception that in 8th the output level first for the front microphone 102 (with SW1 closed and SW3 open) and subsequently for the rear microphone (with SW3 closed and SW1 open). Also in the calibration stage the 8th Both programmable resistors PR3 and PR5 are adjusted until the measured level of the rear microphone closely adjusts the measured level of the front microphone.

In each of the calibration levels can the programmable resistors be adjusted in any suitable manner, such as this will be understood by those skilled in the art becomes, for example, in a hands-free manner (heap-art), a mixed type (merge-art) or fast type (quick-art).

Once the calibration steps of the 6 - 8th The settings for PR2, PR3, PR4 and PR5 remain the same for all modes of operation, except where the programmable resistors also operate as the programmable switches - in which case the programmable resistors are also set to an open circuit setting (infinite resistance), when the switch is set to open. As noted above, the settings of PR1 and PR6 may change for different modes of operation.

While preferred Embodiments of Have been described, these are only illustrative, and not restrictive, and the present invention is intended to be only by the attached claims is defined.

Claims (17)

A microphone system comprising: (a) a first omnidirectional microphone for receiving an acoustic signal and generating an electrical signal in response thereto; (b) a second omnidirectional microphone for receiving the acoustic signal and generating a second electrical signal in response thereto, the first and second microphones being proximate to a surface of a housing for the microphone system and separated by a certain distance on that housing ; (c) a programmable amplifier circuit coupled to the first and second microphones to produce an adjustably delayed version of the second electrical signal and to adjust the sensitivity of the first microphone to the sensitivity of the second microphone in accordance with bring about; and (d) switching means, coupled to the programmable circuit, for selectively generating a first mode signal and / or a second mode signal at a node, the first mode signal including a sum of the first electrical signal and the second electrical signal, and second mode signal includes a sum of the first electrical signal and the delayed version of the second electrical signal. The microphone system of claim 1, further comprising: (E) a programmable low-frequency equalization circuit having a Input connected to the input node and an output for providing an output signal that is programmable variable size one Low frequency equalization. Microphone system according to claim 2, wherein the equalization circuit provides the output signal without low frequency equalization, when the first mode signal is provided at the node, and the equalization circuit outputs the output signal with a desired one Size one Low frequency equalization provides when the second mode signal is generated at the node Microphone system according to claim 1, wherein the second Operating mode signal a desired Directional characteristic generated in relation to the acoustic signal. Microphone system according to claim 1, wherein the switching device optionally at least one of the first mode signal, the second Mode signal, a third mode signal and a fourth Operating mode signal provides at the node, the third Mode signal the first electrical signal and the fourth mode signal the contains second electrical signal. A microphone system according to claim 5, further comprising a T-coil input for receiving a T-coil input signal, and wherein the switching means optionally at least one of first mode signal, the second mode signal, the third Mode signal, the fourth mode signal and a fifth mode signal at the node, the fifth mode signal being the T-coil input signal contains. Microphone system according to claim 6, wherein the programmable Circuit continues to contain a circuit that has a variably damped version of the T-coil input signal generated. Microphone system according to claim 7, wherein the switching device optionally at least one of the first mode signal, the second Mode signal, the third mode signal, the fourth mode signal, of the fifth Mode signal, a sixth mode signal, a seventh Mode signal, an eighth mode signal and a ninth Operating mode signal provides at the node, the sixth Mode signal of a sum of the first mode signal and the variably damped Version of the T-coil input signal contains the seventh mode signal is a sum of the second mode signal and the variable steamed Version of the T-coil input signal contains the eighth mode signal Sum of the third mode signal and the variable attenuated version of the T-coil input signal and the ninth mode signal a sum of the fourth mode signal and the variable attenuated version of the T-coil input signal. The microphone system of claim 1, further comprising a T-coil input for receiving a T-coil input signal, and wherein the switching means optionally at least one of first mode signal, the second mode signal and a third mode signal at the node provides, wherein the third mode signal includes the T-coil input signal. A microphone system according to claim 9, wherein the programmable Circuit continues to contain a circuit that has a variably damped version of the T-coil input signal generated. Microphone system according to claim 11, wherein the switching means optionally at least one of the first mode signal, the second Mode signal, the third mode signal, a fourth Mode signal and a fifth Operating mode signal provides at the node, the fourth Mode signal is a sum of the first mode signal and the variably damped Version of the T-coil input signal and the fifth mode signal a sum of the second mode signal and the variable attenuated version of the T-coil input signal. The microphone system of claim 1, wherein the programmable circuit includes: (a) a first programmable resistor connected between the first omnidirectional microphone and the node; (b) a series combination of a delay stage and a second programmable resistor, the series combination being connected between the second omnidirectional microphone and the node and the delay stage including a third programmable resistor; (c) an invariable resistance between the second omnidirectional microphone and the node is connected. A microphone system according to claim 12, wherein the series combination continue with a fourth programmable resistor in series with the second programmable resistor and the delay stage contains. The microphone system of claim 1, further comprising means for communicating with a programmable microprocessor. Microphone system according to claim 1 for use with a Hearing aid. Method for calibrating a microphone system according to claim 12, comprising the following steps: (a) Adjust of the first programmable resistor such that the sensitivity of the first microphone matches the sensitivity of the second microphone, when the first mode signal is provided at the node; (B) Setting the second programmable resistor such that the sensitivity of the first microphone matches the sensitivity of the second microphone, when the second mode signal is provided at the node becomes; (c) Setting the third programmable resistor such that when the second mode signal is provided at the node the second mode signal will be a desired directional response in relation to the acoustic signal for any value of Distance between the first and the second omnidirectional Microphone generated. Method for calibrating a microphone system according to claim 13, comprising the following steps: (a) Adjust of the first programmable resistor such that the sensitivity of the first microphone matches the sensitivity of the second microphone, when the first mode signal is provided at the node; (B) Setting the second and fourth programmable resistors such that the Sensitivity of the first microphone with the sensitivity of the second Microphones matches, when the second mode signal is provided at the node becomes; (c) Setting the third programmable resistor such that when the second mode signal is provided at the node the second mode signal will be a desired directional response in relation to the acoustic signal for any value of Distance between the first and the second omnidirectional Microphone generated.