Abstract: A terminal identification method is provided which enables two-way communications between terminals and a network while identifying terminal IDs and protecting privacy. Also, authentication method and system are provided which require no complicated calculating process, less steps and smaller amount for wireless communications, and less power consumption. A server and terminal share a hash function and an initial value determined for each terminal, calculate the same temporary ID by hashing the initial value the same number of times with the hash function, and identify the terminal using the calculated temporary ID. The server and the terminal also hold a common hash function and authentication information, acquire an authenticating communication parameter from communication parameters temporarily common during communication, and generate an authentication key using the authentication information, the authenticating communication parameter, and the hash function.

Abstract: Techniques for performing scrambling and descrambling in a communication system are described. In an aspect, different scrambling sequences for different channels and signals may be generated based on different cyclic shifts of a base scrambling sequence, which may be a maximal-length sequence. A scrambling sequence for a given channel may be generated by (i) determining a sequence selector value based on a channel type value and at least one parameter value for the channel and (ii) cyclically shifting the base scrambling sequence based on the sequence selector value. In another aspect, a reference signal sent on variable system bandwidth may be generated with two scrambling sequences, which may be different cyclic shifts of a base scrambling sequence. Scrambling/descrambling for positive and negative frequencies for the reference signal may be performed with the first and second scrambling sequences, respectively.

Abstract: Various embodiments relate to wireless communications, and more particularly, to methods and apparatus for authorizing use of spectrum, e.g., through the issuance of spectrum access keys, and/or preventing or discouraging the unauthorized use of licensed spectrum. Peer to peer wireless communications between authorized users of licensed spectrum may involve scrambling/descrambling of information communicated between authorized devices. In some embodiments air interface timing and/or other information received from a second device, e.g., a beacon or GPS transmitter, is incorporated into a computation of a pseudo-random bit sequence which is also computed based on a spectrum access key communicated to authorized spectrum users.

Abstract: A method and apparatus for performing an automatic wireless connection with a second digital device by a first digital device is provided. The method includes acquiring, by the first input device, random information used for the wireless connection; checking a status of a Wireless Local Area Network (WLAN); storing the checked status; setting the WLAN to an Ad-hoc mode; setting a Service Set Identifier (SSID) of the WLAN using the random information; setting a security key of the WLAN using the random information; and setting an Internet Protocol (IP) address of the WLAN using the random information.

Abstract: Disclosed is a method for transitioning a remote station from a current serving network node having an enhanced security context to a new serving network node. In the method, the remote station provides at least one legacy key, and generates at least one session key based on an information element associated with the enhanced security context. The remote station forwards a first message having the information element to the new serving network node. The remote station receives a second message, from the new serving network node, having a response based on either the legacy key or the session key. The remote station determines that the new serving network node does not support the enhanced security context if the response of the second message is based on the legacy key. Accordingly, the remote station protects communications based on the legacy key upon determining that the enhanced security context is not supported.

Abstract: A method for verifying the integrity of a key implemented in a symmetrical ciphering or deciphering algorithm, including the steps of complementing to one at least the key; and verifying the coherence between two executions of the algorithm, respectively with the key and with the key complemented to one.

Abstract: A computer system having at least first and second documents, a plurality of decryption keys, and a plurality of data segments stored therein is provided. Each of the plurality of data segments is decryptable by a selected one of the decryption keys. The decryption keys include a first set of decryption keys associated with the first document and not associated with the second document, a second set of decryption keys associated with the second document and not associated with the first document, and a third set of decryption keys associated with the first document and the second document. The first document is deleted, and in response, the first set of decryption keys is rendered unusable, and the second set of decryption keys and the third set of decryption keys are not rendered unusable.

Abstract: Providing revocation status of at least one associated credential includes providing a primary credential that is at least initially independent of the associated credential, binding the at least one associated credential to the primary credential, and deeming the at least one associated credential to be revoked if the primary credential is revoked. Providing revocation status of at least one associated credential may also include deeming the at least one associated credential to be not revoked if the primary credential is not revoked. Binding may be independent of the contents of the credentials and may be independent of whether any of the credentials authenticate any other ones of the credentials. The at least one associated credential may be provided on an integrated circuit card (ICC). The ICC may be part of a mobile phone or a smart card.

Abstract: The present invention encompasses an electronic device, such as a server, which may be operated in a communication system. The electronic device comprises a method for receiving a request from another electronic device to transmit keys, for example a mobile terminal. Responsive to the request, the server generates the required keys and determines a best time to send the keys to the mobile client device such that a new connection is not required just for sending the requested keys. The best time to send the keys may be during a scheduled connection for sending non-key data, for example a connection setup for transmitting system parameters, content data, etc. By sending the keys along with the non-key data, a need for a special connection is avoided.

Abstract: A group key management approach based on linear geometry is disclosed.

Abstract: Secure information is managed for each host or machine in an electronic environment using a series of key identifiers that each represent one or more secure keys, passwords, or other secure information. Applications and services needing access to the secure information can specify the key identifier, for example, and the secure information currently associated with that identifier can be determined without any change to the code or manual input or exposure of the secure information on the respective device. Functionality such as encryption key management and rotation are inaccessible and transparent to the user. In a networked or distributed environment, the key identifiers can be associated with host classes such that at startup any host in a class can obtain the necessary secure information. Updates and key rotation can be performed in a similar fashion by pushing updates to host classes transparent to a user, application, or service.

Abstract: A method for control ling information object (102) usage in a network of information (100) wherein information objects (102) are identified by information object identities and locations of the information objects (102) are indicated by location pointing information, the method comprising receiving (5b) an encrypted information object (102), sending (7) to a resolution node (D200) a request for location pointing information of a key issuing node (D300), the request comprising an identity of the received information object (102), receiving (8) the location pointing information of the key issuing node (D300), sending (9) to the key issuing node (D300) a request for an access key (104) for decrypting the encrypted information object (102), the request comprising the identity of the received information object (102), receiving (11) the access key (104), and decrypting (12) the received encrypted information object (102) with the received access key (104).

Abstract: A privacy-preserving device-tracking system and method to assist in the recovery of lost or stolen Internet-connected mobile devices. The function of such a system seem contradictory, since it is desirable to hide a device's legitimately-visited locations from third-party services and other parties to achieve location privacy, while still enabling recovery of the device's location(s) after it goes missing by tracking the device to determine its location. An exemplary embodiment uses a DHT for storing encrypted location information and other forensic information in connection with indices that are successively determined based on initial pseudorandom seed information (i.e., state) that is retained by the owner of the device. Using the seed information, the software can determine indices mapped to location information stored after the device went missing, enabling the device to be located.

Abstract: The invention relates to a method and an apparatus in which samples of at least a part of an audio signal of a first channel and a part of an audio signal of a second channel are used to estimate a time delay between said part of the audio signal of said first channel and said part of the audio signal of said second channel. The method includes windowing the samples; performing a time-to-frequency domain transform; and determining an inter-channel time delay between said part of the audio signal of the first channel and said part of the audio signal of said second channel on the basis of the frequency domain representations. There is also disclosed a method and an apparatus for decoding the encoded samples.

Abstract: Provided is a method for controlling synchronizing downmix signals and MPEG surround side information signals by controlling a delay according to the kind of downmix audio signals in an MPEG surround decoder. When multi-channel audio signals are restored using an HE-AAC decoder and a low-power MPEG surround decoder and complex QMF signals outputted from the HE-AAC decoder are used as downmix signals, a delay unit compensates for a delay caused in a real-to-complex converter. Anther delay unit delays spatial parameters to compensate for a delay caused in QMF and Nyquist banks when time-domain downmix signals are used. Also, when multi-channel audio signals are restored using an HE-AAC decoder and a high-quality MPEG surround decoder and complex QMF signals outputted from the HE-AAC decoder are used as downmix signals, a delay unit compensates for a delay caused in a real-to-complex converter.

Abstract: A recorder (10) for recording a scene (12) includes an apparatus frame (218), an optical assembly (220), an image system (222), a position assembly (243), an audio system (224), and a compensation system (248). The image system (222) captures an image (252) of the scene (12). The position assembly (243) can be an autofocusing assembly (244) that focuses the optical assembly (220) on a subject (16) of the scene (12). The position assembly (243) generates position information relating to the position of the subject (16) relative to the recorder (10). The audio system (224) captures a captured sound from the scene (12). The compensation system (248) evaluates the position information and the captured sound from the scene (12) and provides an adjusted sound track in view of the position information.

Abstract: Automatic measurements are made of audio presence and level in an audio signal by direct processing of an MPEG data stream representing the audio signal, without reconstructing the audio signal. Sub-band data is extracted from the data stream, and the extracted sub-band data is dequantized and denormalized. An audio level for the dequantized and denormalized sub-band data is measured without reconstructing the audio signal. Channel characteristics are used in measuring the audio level of the sub-band data, wherein the channel characteristics are used to weight the measured levels. The measured levels are compared against at least one threshold to determine whether an alarm should be triggered.

Abstract: A personal noise monitoring system and method for operating the same. Sound pressure data from inside the ears of a user of hearing protection device (HPD) are acquired from microphones in the HPD and reported to a master control unit. Simultaneously, the master control unit receives sound pressure data from the ambient environment in which the user is located. The data are reported to a central server for processing. The central server may use the data to determine in near real time or real time whether the user of the HPD is at risk for exposure to excess sound levels and to take remedial action while the user is still in the ambient environment.

Abstract: A method and an arrangement for adapting an alert signal level generated by a device to an ambient of the device is provided. The method may include processing a sound signal corresponding to a test signal or an alert signal, generating a correlation value by correlating the sound signal with a generated sound signal, comparing the correlation value with a value, and adjusting the alert signal to a level based on result of the comparison.

Abstract: A method for testing and calibrating electronic semiconductor components which convert sound into electrical signals acoustically irradiates the components in a sound chamber whose largest free length is less than half the wavelength of the highest frequency of the sound waves produced during the test.

Abstract: A mobile device includes at least one speaker and an audio subsystem for providing an audio signal to the at least one speaker for playback by the at least one speaker. The audio subsystem operates by detecting a distance to a user of the mobile device using a proximity sensor and controlling volume output of the at least one speaker based on the distance to the user of the mobile device and the operational status of the proximity sensor. If it is determined that the proximity sensor is functional, the audio subsystem applies a gain factor to the audio signal that varies based on the distance to the user or limits the maximum allowable speaker output based on the distance. A high or low gain setting may be applied for when the user is far away or in close proximity to the mobile device.

Abstract: The initial values of parameter estimates are set, including reverberation parameter estimates, which includes a regression coefficient used in a linear convolutional operation for calculating an estimated value of reverberation included in an observed signal, source parameter estimates, which includes estimated values of a linear prediction coefficient and a prediction residual power that identify the power spectrum of a source signal, and noise parameter estimates, which include noise power spectrum estimates. Then, the maximum likelihood estimation is used to alternately repeat processing for updating at least one of the reverberation parameter estimates and the noise parameter estimates and processing for updating the source parameter estimates until a predetermined termination condition is satisfied.

Abstract: Method, user terminal and computer program product for controlling audio signals at the user device during a communication session between the user device and a remote node, in which a primary audio signal is received at audio input means of the user device for transmission to the remote node in the communication session. It is determined whether the user device is operating in (i) a first mode in which secondary audio signals output from the user device are likely to disturb the primary audio signal received at the audio input means, or (ii) a second mode in which secondary audio signals output from the user device are not likely to disturb the primary audio signal received at the audio input means.

Abstract: Systems and methods described herein provide for low latency active noise cancellation which alleviate the problems associated with analog filter circuitry. The present technology utilizes low latency digital signal processing techniques which overcome the high latency conventionally associated with conversion between the analog and digital domains. As a result, low latency active noise cancellation is performed utilizing digital filter circuitry which is not subject to the inaccuracies and drift of analog filter components. In doing so, the present technology provides robust, high quality active noise cancellation.

Abstract: A personal audio device, such as a wireless telephone, includes noise canceling circuit that adaptively generates an anti-noise signal from a reference microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. A processing circuit monitors a level of the anti-noise signal, determines that the anti-noise signal may cause damage to the transducer and adjusts the generation of the anti-noise signal such that damage to the transducer is prevented.

Abstract: An active noise control apparatus includes a first active noise controller for generating a first canceling signal for a first noise type, a second active noise controller for generating a second canceling signal for a second noise type that is different from the first noise type, a mixer for mixing the first canceling signal and the second canceling signal into a mixed canceling signal, a canceling sound output unit for outputting a canceling sound based on the mixed canceling signal, and an amplitude suppressor for suppressing the amplitude of the second canceling signal depending on the amplitude of the first canceling signal.

Abstract: A loudspeaker arrangement in a motor vehicle includes at least one loudspeaker, which is able to be driven by an audio processor, the loudspeaker being arranged as at least one electrostatic planar loudspeaker.

Abstract: A system to occlude an ear canal is provided. The system includes an expandable device, a reservoir, a channel coupled between the expandable device and the reservoir, and a pump. The pump expands the expandable device such that a surface of the expandable device contacts an ear canal wall and imparts a force onto the ear canal wall, to produce a tensional strain in the ear canal wall. The strained ear canal wall impedes bodily-propagated sound from entering the ear canal through the ear canal wall, to reduce an occlusion effect by the bodily-propagated sound.

Abstract: A headset is described. The headset includes a headset insert worn on a head of a user. The headset insert includes a first connector having a first mechanical coupler. The first connector is configured to mate in at least two different orientations with a second connector having a second mechanical coupler. A frame includes the second connector that mates with the first connector. The frame is adapted to receive the headset insert in at least two different orientations.

Abstract: There is provided an information processing apparatus including microphones, a parameter setting unit, and an audio signal processing unit. At least one pair of the microphones are provided, and the microphone picks up external audio to convert the external audio into an audio signal. The parameter setting unit sets a processing parameter specifying at least the sensitivity of the microphone according to at least an instruction from a user. Based on the processing parameter, the audio signal processing unit applies processing, including beamforming processing, to the audio signal input from the microphone.

Abstract: A feedback-controlled microphone includes a microphone body and a membrane operatively connected to the body. The membrane is configured to be initially deflected by acoustic pressure such that the initial deflection is characterized by a frequency response. The microphone also includes a sensor configured to detect the frequency response of the initial deflection and generate an output voltage indicative thereof. The microphone additionally includes a compensator in electric communication with the sensor and configured to establish a regulated voltage in response to the output voltage. Furthermore, the microphone includes an actuator in electric communication with the compensator, wherein the actuator is configured to secondarily deflect the membrane in opposition to the initial deflection such that the frequency response is adjusted. An acoustic beam forming microphone array including a plurality of the above feedback-controlled microphones is also disclosed.

Abstract: A signal processing device for supplying sound signals to a first speaker for emitting a sound on a low-pitched sound side and a second speaker for emitting a sound on a high-pitched sound side higher than the low-pitched sound side, includes a control portion that controls a characteristic of the sound signal supplied to the first speaker so that an output level of the first speaker is maintained at a crossover frequency between the first speaker and the second speaker, when an output level of the sound signal supplied to the first speaker is changed.

Abstract: A low powered guitar amplifier is disclosed that can generate the overdriven tones of much larger class ab push-pull amplifiers and attenuate them further with an attenuator that leaves the tone and feel intact. This amplifier uses a cathode follower output stage FIG. 1. 12 to generate these powerful tones and a non intrusive attenuation circuit FIG. 2. 46 that benefits from the unique properties of the cathode follower output stage regardless of configuration or topology. These benefits are the ability to drive any impedance above the selected output impedance and no need to maintain a constant impedance therefore utilizing a simple series attenuation circuit whereby substantially all the current is seen in the speaker load and therefore the output stage interaction between the amp and musician is left intact.

Abstract: The present technology relates generally to a closed-loop power stage and audio amplifier circuits comprising the same. The present technology further provides a method for controlling an amplifier circuit. The closed-loop power stage is configured to receive a PWM input signal having a first frequency and a first duty cycle, a power supply voltage, and a bias signal related to the power supply voltage, and to output a square-wave signal having a second frequency and a second duty cycle. The closed-loop power stage comprises a feedback loop which is configured to regulate the second duty cycle of the square-wave signal in response to a variation in the power supply voltage. The audio amplifier circuit comprising the closed-loop power stage may have a stable output voltage and thus have good power supply rejection performance.

Abstract: A low-noise pre-amplifier with an active load element is integrated into a microphone. The microphone has an acoustic sensor coupled to the intrinsic pre-amplifier. A controllable current source is coupled to the intrinsic pre-amplifier and supplies a pre-amplifier bias current. A current source controller is coupled to the current source and controls the amplitude of the pre-amplifier bias current to maintain the intrinsic pre-amplifier at a bias point at which the intrinsic pre-amplifier amplifies microphone signals produced by the acoustic sensor. The intrinsic pre-amplifier may be actively regulated at the pre-determined bias point using negative feedback. Alternatively, the intrinsic pre-amplifier may be set to the pre-determined bias point by sweeping the pre-amplifier bias current for the intrinsic pre-amplifier over a range of currents.

Abstract: The Christmas tree is a fake Christmas tree rotatably engaged with respect to a stand having rotating means integrated thereon. The stand features a USB port and MP3 dock that enables audio to be played upon speakers vertically arranged upon said tree. The Christmas tree shall be either permanently or temporarily affixed to said stand. The rotating means of the stand consist of a motor and gearing system that can optionally provide different rates of rotation of said Christmas tree. An optional light system may be included to illuminate said Christmas tree.

Abstract: A condenser microphone unit includes a diaphragm; a fixed electrode defining a capacitor together with the diagram; a cylindrical electrode having a first end and a second end, the first end being fitted to the periphery of the fixed electrode; a circuit board in contact with a second end of the cylindrical electrode, the circuit board being electrically connected to the cylindrical electrode; a unit casing accommodating the diaphragm, the fixed electrode, the cylindrical electrode, and the circuit board; and a hollow insulating air chamber provided between the internal peripheral surface of the unit casing and the external peripheral surface of the cylindrical electrode.

Abstract: A condenser microphone includes a plurality of condenser microphone units, each unit including a diaphragm and a fixed electrode one of which has an electret layer thereon. The condenser microphone units include respective sensitivity controllers changing sensitivities of the units. The sensitivity controllers include respective variable resistors connected between a power source and a ground. Each of the variable resistors has a slidable terminal connected to one, opposed to the electret layer, of the diaphragm and the fixed electrode, of the corresponding condenser microphone unit.

Abstract: A driver arrangement for a speaker array (201) comprises a first and second driver (301, 303) each arranged with an on-axis direction at an angle to an on-axis direction of the speaker array (201). The first driver angle exceeds 5° and the second driver angle exceeds the first angle. A front section of each driver (301, 303) comprises a front edge of a radiating element and parts of the driver in front thereof. The drivers (301, 303) are arranged at least partly inline such that a first distance from a front axis (311) perpendicular to an on-axis of the speaker array (201), and intersecting a furthest forwards part of the first driver front section, to a closest part of the second driver front section is lower than a second distance from the front axis (311) to a furthest part of the first driver front section. The combination of angled drivers and the inline arrangement provides improved performance.

Abstract: An audio reproduction apparatus includes: a delay equalizer (301), a delay equalizer (303), a level adjuster (314), and a level adjuster (317). The delay equalizer (301) equalizes an FL signal using an equalizer characteristic EQ9 that converts a characteristic of an audio signal perceived as being reproduced at a position of an FL speaker (104) with respect to a viewing position to be perceived as being reproduced at a position of a virtual speaker (201) with respect to the viewing position. The delay equalizer (303) equalizes the FL signal using an equalizer characteristic (EQ12) that converts a characteristic of an audio signal perceived as being reproduced at a position of an SL speaker (106) with respect to a viewing position to be perceived as being reproduced at a position of the virtual speaker (201) with respect to the viewing position. The level adjuster (314) performs level adjustment, using a first coefficient K9, on an output signal of the delay equalizer (301).

Abstract: A method for the operation of a hearing device with at least one receiver includes carrying out a fixed second frequency shift of an electrical receiver signal supplying the receiver or of a predefinable frequency range of the receiver signal and a variable first frequency shift of the receiver signal or of a predefinable frequency range of the receiver signal. The first frequency shift is changed depending on the occurring feedback. A frequency shift which effectively prevents feedback is advantageously carried out, while artifacts of the frequency shift are minimized.

Abstract: The adjustment of the signal processing carried out by a hearing aid to the individual hearing loss of a user is intended to be simplified. For this purpose, a number of predefined adjustment programs, from which the user selects a suitable program by operating an operating element, are provided in the hearing aid. Neither a visit to a hearing aid acoustician nor special adjustment devices is/are required for adjustment.

Abstract: A deep-ear-canal hearing device is worn deep in the ear canal of a user. The hearing device is easy to produce and use, has a small overall size, and can be comfortably worn deep within the auditory canal, in particular in the bony part of the auditory canal as well. The hearing device has a housing, a signal-processing apparatus, and a receiver. The signal-processing apparatus is arranged within the housing. The receiver is merely arranged partly within the housing and another part is arranged outside of the housing. The receiver only being arranged partly within the housing, it is thus not completely surrounded by the housing. Hence, the housing can have a smaller configuration. In the region where the receiver is arranged outside of the housing, the double wall in the form of, the receiver wall and, the housing wall can be dispensed with, which helps in reducing the size.

Abstract: A hearing aid kit includes a standard fit, completely-in-canal (CIC) hearing aid and a hearing aid tool set. The CIC hearing aid is for extended use and includes a core module inserted into a sleeve. The core module and the sleeve each include various features providing for a minimum overall size, ease of insertion, removal, and cleaning, and enhanced sound transmission. The tool set is configured to be stored and carried in a single piece and provides for adjustment and cleaning of the CIC hearing aid. Open ear fits and occlusive ear fits are possible using different sleeves.

Abstract: A hearing aid retainer accessory to be used together with a hearing aid is provided having a housing with a relatively large diameter longitudinal end face portion and a relatively smaller diameter hook-end to which a hook is attached. The hearing aid retainer accessory comprises an elongated string with a first end portion and a second portion, a first attaching means connected to the first end portion and a second attaching means connected to the second portion, wherein the first attaching means is attachable to a hook of a hearing aid, the second attaching means is attachable to a longitudinal end face portion of a housing of a hearing aid, such that a retaining ring is formed of both the geometry of a hearing aid and the elongated string.

Abstract: A hearing aid retainer accessory is provided for use with a hearing aid having a housing with a longitudinal end face portion comprising a mechanical connection terminal and an electrical connection point. The hearing aid retainer accessory comprises a retainer element with a first end face portion having a first mechanical connection means configured to be engageable to a mechanical connection terminal of a longitudinal end face portion of a housing of a hearing aid.

Abstract: A safety device reversibly attachable to any hearing aid of a type having a behind the ear unit with a connecting member and an ear bud prevents the hearing aid from being lost or damaged if the unit is dislodged from behind the ear of the wearer. The device is virtually invisible so as not to draw attention to the fact that the wearer is using a hearing aid. One portion of a two part attaching strip is adhered to the behind the ear unit. The second portion can be securely and reversibly united with the first portion to attach or remove the device from the hearing aid. A transparent filament is integral with the second portion at one end and to a securing plate at the opposing end. The securing plate can receive the temple of a pair of glasses or another retaining article worn on the person of the wearer. A slit in the securing plate is opened by pressure on the side rim enabling the insertion of the retaining article which is held securely when the pressure is removed and the slit closed around it.

Abstract: A cone speaker that outputs audio by transmitting to a truncated cone, the movements of a voice coil driven when an audio current is transmitted through a voice coil placed inside a magnetic circuit formed in a space that surrounds a pole piece. Inside a space between the back surface of a center cap attached to a central portion of the cone and the apical surface of the pole piece that faces the center cap, a first filling material composed of a flexible porous body with a low porosity fills the periphery of the space and a second filling material composed of a flexible porous body with a higher porosity than the first filling material fills the central portion thereof.

Abstract: One embodiment of the invention discloses a speaker box having a housing and a speaker accommodated in the housing. The speaker includes a sound radiation surface for generating sound. The housing includes a first and second output ports disposed at one side of the housing for transmitting the sound to outside of the speaker box. The housing includes a plurality of ribs disposed therein and forming a bending channel. The first and second output ports are disposed at two ends of the bending channel. The bending channel is divided into a front channel and a back channel by the speaker. The speaker box is capable of obtaining a better low frequency sound reproduction quality.

Abstract: A unidirective condenser microphone unit includes a diaphragm; a fixed electrode facing the diaphragm with a gap and defining a capacitor together with the diaphragm; an insulating spacer disposed adjacent to the rear surface of the fixed electrode and supporting the fixed electrode; an acoustic resistor disposed in an air chamber defined by the front surface of the insulating spacer and the fixed electrode; a unit case, a front acoustic terminal; and a rear acoustic terminal. The insulating spacer has a protrusion projecting toward the fixed electrode with a gap, and the protrusion is fixed to the surface of the fixed electrode with fixing material.