1. A hearing instrument microphone device, the microphone device comprising at least two microphone ports, a pressure difference microphone in communication with at least two of the ports and a pressure microphone in communication with at least one of the ports, wherein the acoustic center of the ports in communication with the pressure microphone is essentially at equal distances from locations of the ports in communication with the pressure difference microphone.
2. The microphone device according to claim 1, wherein the pressure microphone and the pressure difference microphone are arranged in a common casing.
3. The microphone device according to claim 1, wherein the pressure difference microphone comprise a pressure difference microphone cartridge with a membrane dividing the volume within the cartridge in two volume parts, the first volume part being, via a first opening of the pressure difference microphone, coupled to a first one of the ports, whereas the second volume part is, via a second opening of the pressure difference microphone, coupled to a second one of the ports.
4. The microphone device according to claim 1, wherein the pressure microphone is a pressure microphone comprising a pressure microphone cartridge, and a membrane dividing the cartridge volume in two volume parts, the first volume part being, via at least one pressure microphone opening, coupled to at least one of the ports, whereas the second volume part is closed.
5. The microphone device according to claim 1, wherein membranes of the pressure microphone and of the pressure difference microphone are parallel.
6. The microphone device according to claim 1, wherein the pressure difference microphone and the pressure microphone are both coupled to the same plurality of ports.
7. The microphone device according to claim 1, wherein the pressure difference microphone is coupled to two pressure difference microphone ports and wherein the pressure microphone is coupled to at least one pressure microphone port separate from the pressure difference microphone ports.
8. A hearing instrument comprising a microphone device according to claim 1 and further comprising a signal processor and a receiver, the signal processor capable of processing the signals produced by the microphones in response to an incident acoustic signal, of combining these signals into a processed signal with an adjustable directional dependency, and of activating the receiver to convert an electronic output signal produced by the signal processor into an acoustic output signal.
9. The hearing instrument according to claim 8, wherein the signal processor is capable of applying a correction filter to at least one of the pressure microphone signal and the pressure difference microphone signal, prior to combining the signals.
10. A hearing instrument comprising a pressure difference microphone, a pressure microphone, and a signal processor, the signal processor being capable of obtaining a first digital input signal representative of a sound signal incident on the pressure microphone and a second digital input signal representative of a sound signal incident on the pressure difference microphone, and of processing the first and second signals into an output signal, the signal processor comprising a correction filter adjusting a frequency dependency of at least one of the first and the second output signals into an adjusted first or second input signal, respectively; and a beamformer capable of combining the adjusted first and second signals onto a beamformed signal with an adjustable directional dependency.
11. The hearing instrument according to claim 10, wherein one of the following conditions is fulfilled:
the acoustic center of the microphone ports in communication with the pressure microphone is essentially at equal distances from the locations of the microphone ports in communication with the pressure difference microphone;
an electronic delay compensation is established to compensate for a sound path difference of sound incident on the directional microphone and of sound incident on the pressure microphone arising from different acoustic centers of the pressure microphone and the pressure difference microphone.
12. The hearing instrument according to claim 10, wherein the beamformer is an adaptive beamformer.
13. The hearing instrument according to claim 10, wherein the pressure difference microphone and the pressure microphone are part of a microphone device according to claim 1.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical wavelength monitoring system, comprising:
a master unit, comprising:
a wavelength swept optical source;
a detection unit;
a processing unit; and
a wavelength reference unit producing a reference signal related to the wavelength output of the optical source;
at least one slave unit, comprising:
a detection unit; and
a processing unit;
a communication arrangement providing at least transfer of information from the master unit to the slave unit; and
a light coupling arrangement for coupling light from the optical source into at least one string of optical sensors and for coupling light reflected from the at least one string of optical sensors, wherein the detection units of the slave and master are arranged to detect portions of reflected light.
2. The optical wavelength monitoring system of claim 1, wherein the reference signal is digitized and transferred from the processing unit of the master unit to the processing unit of the at least one slave unit via the communication arrangement.
3. The optical wavelength monitoring system of claim 1, wherein the reference signal is transferred to the processing units of the master and the at least one slave units.
4. The optical wavelength monitoring system of claim 1, wherein information related to the reference signal is processed by the processing unit of the master unit and is communicated to the at least one slave unit.
5. The optical wavelength monitoring system of claim 1, wherein the reference signal comprises information related to the intensity of light from the wavelength swept optical source with time after interacting with a reference element in the wavelength reference unit.
6. The optical wavelength monitoring system of claim 1, wherein a delay exists between equidistant samples in the master and slave processing units and is corrected.
7. The optical wavelength monitoring system of claim 6, wherein a synchronization pulse from the master processing unit is transmitted to the slave processing unit to measure the delay.
8. The optical wavelength monitoring system of claim 7, wherein a delay correction factor based on the synchronization pulse is provided to the slave unit.
9. The optical wavelength monitoring system of claim 1, wherein the reference signal is used to linearize a light sweep from the wavelength swept optical source.
10. The optical wavelength monitoring system of claim 1, further comprising multiple slave units, each having a detection unit arranged to detected portions of reflected light, wherein amplitudes of the master and multiple slave detection units are equalized.
11. The optical wavelength monitoring system of claim 10, wherein the amplitudes are equalized by varying the output power of the optical source with time based on the amplitudes of the master and multiple slave detection units.
12. The optical wavelength monitoring system of claim 1, wherein the light coupling arrangement comprises a circulator configured to receive the reflected light from the at least one string of optical sensors and pass the reflected light to a splitter.
13. The optical wavelength monitoring system of claim 12, further comprising multiple slave units, each having a detection unit, wherein the splitter is configured to divide the reflected light between the multiple slave detection units.
14. The optical wavelength monitoring system of claim 13, wherein the splitter is configured to divide the reflected light unequally between the multiple slave detection units based on a desired signal-to-noise ratio at each of the multiple slave detection units.