EP1484944A2 - Procédé de reproduction d'un signal audio avec un haut-parleur ultrasonore - Google Patents
Procédé de reproduction d'un signal audio avec un haut-parleur ultrasonore Download PDFInfo
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- EP1484944A2 EP1484944A2 EP04021692A EP04021692A EP1484944A2 EP 1484944 A2 EP1484944 A2 EP 1484944A2 EP 04021692 A EP04021692 A EP 04021692A EP 04021692 A EP04021692 A EP 04021692A EP 1484944 A2 EP1484944 A2 EP 1484944A2
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Classifications
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K15/00—Acoustics not otherwise provided for
- G10K15/02—Synthesis of acoustic waves
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R27/00—Public address systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2217/00—Details of magnetostrictive, piezoelectric, or electrostrictive transducers covered by H04R15/00 or H04R17/00 but not provided for in any of their subgroups
- H04R2217/03—Parametric transducers where sound is generated or captured by the acoustic demodulation of amplitude modulated ultrasonic waves
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
- H04R2499/10—General applications
- H04R2499/13—Acoustic transducers and sound field adaptation in vehicles
Definitions
- the invention relates to a method for reproducing audio sound with Ultrasound speakers as well as a construction of the ultrasound speakers and their application.
- the audio spotlight An application of nonlinear interaction of sound waves to a new type of loudspeaker design "is already known, a loudspeaker made up of several ultrasound emitters build. With such ultrasound emitters, audio sound can be combined in one Frequency range are emitted by the audio sound itself no longer from human ear can be perceived. Through nonlinear effects in the Air comes in at high sound pressure and the superposition of two ultrasonic waves audible sound is generated. The higher in comparison to usual audio signals Frequency of ultrasound causes the radiation of the sound because of its small wavelength and the large transducer dimensions of the Ultrasound emitter takes place in a highly spatially directed manner. The frequency dependence of the Directional characteristic of conventional loudspeakers - spherical radiators at low Frequencies, directional emitters at high frequencies - occurs with an ultrasound speaker hardly on.
- the invention has for its object a method for reproducing Audio sound and an ultrasound speaker compared to the previous ones Approaches to improve, so that high quality sound reproduction is possible.
- the object is achieved according to the invention with a method Claim 1 and an ultrasound speaker according to claim 2 solved.
- the method according to the invention combines low-frequency audio sound with the strong directional characteristic of ultrasound.
- the directional characteristic of the loudspeaker is therefore almost independent of the signal frequency.
- the frequencies of these waves correspond to the sum and difference frequencies of the original waves and multiples thereof (n ⁇ ⁇ 1 ⁇ m ⁇ ⁇ 2 where ⁇ 1 and ⁇ 2 are frequencies of the initiated sound waves (tones) and n, m are integers).
- the sum and difference frequencies occur in every frequency range. There are clear advantages over conventional loudspeakers in the ultrasound range in that a very strong directional characteristic of the transducers can be realized and which is outside the human hearing range.
- the initiating signals - i.e. the ultrasonic waves - are inaudible.
- a first tone with a frequency of 200 kHz and a second tone with a frequency of 201 kHz is emitted into the air at high sound pressure, so arise in the overlapping zone of the two tones sum and difference tones.
- This difference tone is much louder than all other tones resulting from the interaction. Sum and difference tones only arise in a nonlinear medium such as air as distortion products.
- the difference tones generated have the property that the spread of the Difference tones (secondary sound) in the direction of the ultrasound to be generated (initiating tones, primary sound). Furthermore, the difference tones are only in the range of the ultrasound is audible, i.e. the directional characteristic of the difference tones corresponds to that of ultrasound. Finally, the sound pressure of the differential tones increases with the frequency of ultrasound.
- the still low-frequency audio signal to be reproduced becomes a Subject to frequency response linearization ( Figure 1, Figure 2).
- This signal will then by a double sideband amplitude modulation with a carrier signal in Ultrasound frequency range linked. Then this ultrasound signal becomes one Dynamics (error compensation (compression)) subjected to the compressed signal subjected to a second frequency response linearization and this signal in turn fed to the ultrasound speaker.
- the ultrasound carrier preferably by a few dB, for example 12dB, is suppressed ( Figure 2).
- the ideal center frequency i.e. the mean between the ultrasound carrier frequency and the sideband frequency (range) of the emitted ultrasound signal results from the intended application.
- the level of the audible sound pressure depends significantly the sound pressure of the ultrasound signal, the non-linearity parameter of the medium, the frequency of the resulting audio signal as well as the distance to the source and the Damping the medium.
- the differential frequency wave DFW - i.e. the audible sound - builds up with increasing distance from the source. Due to the damping of the Ultrasonic wave in the air becomes the greatest sound pressure at a certain distance reached until the level increases again as the distance increases due to damping drops.
- the attenuation of ultrasound in the air depends on the Ultrasound frequency. The higher the frequency, the higher the absorption of ultrasound in air.
- an ideal frequency range from approx. 40kHz to 500kHz (or more) can be specified.
- the frequency range is one hand chosen high enough to generate a DFW and one as effectively as possible to ensure sufficient frequency distance to audible sound, on the other hand but low enough that airborne damping does not have too much of an impact has the audio sound.
- Another criterion is the directional characteristics of the Ultrasonic emitter. The higher the emitted frequency, the more directional it is the radiation.
- the frequency shift of the low-frequency signal (speech, music, noises, Sounds) in the ultrasound range is done by amplitude modulation.
- the carrier signal e.g. 200kHz and the lower sideband emitted via a converter and in the air superimposed.
- the non-linear behavior of the air creates a signal whose Frequency corresponds to the difference between the carrier and sideband frequencies.
- the sound pressure of the differential tones increases quadratic with the difference frequency of the emitted ultrasound tones.
- the sound pressure of the differential frequencies results, among other things, from the product of the signals to be mixed.
- the carrier When an amplitude-modulated signal is emitted, the carrier is emitted in full even in the case of a modulation pause, ie when there is no signal at the modulator.
- the amplitude of the wearer means constant noise pollution for the ears and permanent electrical stress on the transducers.
- the carrier is continuously emitted and has a greater amplitude than the sideband that is modulated in time with the low frequency.
- a noise reduction can be achieved if the amplitude of the carrier is reduced, for example by a filter or already in the modulator by partial carrier suppression, and at the same time the amplitude of the upper sideband is increased. This reduces the continuous level and increases the relative carrier-related change in the level due to the modulation. In the event of carrier suppression, the lower sideband must be strongly suppressed to prevent mixing of the two sidebands with one another, which would cause severe distortion.
- carrier reduction The measure described above can also be generally referred to as "carrier reduction”.
- the carrier amplitude is modulated with the amplitude of the signal to be transmitted, in the event of a pause in modulation, no signal is emitted. Then is required an additionally controlled compressor stage that compensates for amplitude errors that occur result from the modulation of the carrier. To eliminate the above So a problem can be a modulation of the carrier amplitude in time with the modulating signal can be made.
- a problem described above can be countered by a Compression of the signal to be modulated is achieved so that the signal in its dynamics is reduced and in particular the quiet signal passages in their volume can be raised. This makes the modulator optimal disqualify. After the modulation, the compression must be done by an expansion be balanced again to maintain the original dynamics. With the compression of the modulation signal described before the modulation could very good results are achieved.
- Modulation breaks to control the converter with the carrier signal suppress (mute) so that the modulator output signal disappears if there is no input signal.
- the amplitude-modulated low-frequency vibration is associated with high sound pressure radiated from a converter.
- a difference frequency spectrum that corresponds to the spectrum of the low frequency.
- single sideband modulation is particularly preferred Way suitable.
- the carrier is in an ordinary double sideband amplitude modulation is partially suppressed, so is a suppression of the lower one Sideband indispensable because the mixture of the two sidebands with each other causes additional difference frequencies, which is in the form of a harmonic distortion undesirably noticeable.
- the radiation of the modulated signal is like this narrow band, that the lower sideband is only reproduced very quietly.
- the Mixing the side bands with each other is therefore sound pressure negligible. But that presupposes that the carrier is so loud that the mixture of carrier and sideband gives a much louder signal than the mixture of Sidebands with each other.
- the modulation is therefore either as ordinary Double sideband amplitude modulation realized or as single sideband amplitude modulation, in which the carrier for further functional optimization for example 12dB is suppressed.
- the Equalization can take place before the modulation in the low frequency range or after the Modulation in the ultrasound range. Equalization after modulation has the advantage that thereby the modulation reserve of the modulator when a Frequency range is not restricted.
- the difference sound wave arises in the emitted ultrasound cone.
- the cross section of the Kegels has an influence on the resulting audio frequency response.
- the audible signal is created at the interface that is held into the sound beam.
- the lower limit frequency depends on the cross-sectional area of the beam brought object.
- the maximum of the sound pressure results at a certain distance from the Ultrasound source. It occurs in different audio frequencies Distances on.
- a linear frequency response can therefore be for a specific one Only set the distance using a special distance-related equalization.
- the Signal processing therefore has to be special for a linear frequency response include distance-dependent frequency response equalization.
- the described analog amplitude modulation can also be implemented digitally.
- Frequency response contours can also be used when using a Perform digital signal processor relatively easily.
- the audio sound pressure can also be further increased by other measures become. Due to the increasing division of the wavefront in the course of Propagation, which is synonymous with the creation of harmonics. After a Energy balance does not stand for the energy that is in the harmonics Difference sound wave available. In a way, there is an energy flow from the Fundamental to the harmonics. If it succeeds in stopping this flow of energy, so the audio sound pressure could be increased. A realization suggests this as follows:
- a sound-permeable medium contains small cavities, which together with the Material results from a variety of Helmholz resonators.
- the resonators are on the tuned the first harmonic of the signal and thereby slow down the energy flow higher harmonics. If the cavities are filled with a non-linear medium, e.g. a liquid, this measure allows a higher value for the Achieve nonlinearity parameters, which increases the sound pressure of the differential tones would.
- This technology makes it possible to build reflectors that passively pass through Increase the sound pressure of the differential tones.
- the frequencies of these waves correspond to the sum and difference frequencies of the original waves and multiples thereof. (n * ⁇ 1 ⁇ m ⁇ 2 with ⁇ 1 , ⁇ 2 : frequencies of the initiated tones and n, m: gaäne numbers).
- Figure 1 and Figure 2 show block diagrams of an ultrasonic speaker, wherein Figure 2 shows an improved circuit compared to Figure 1.
- the low-frequency audio signal becomes one Subjected to frequency response linearization and then double sideband amplitude modulation (and / or a frequency and / or phase modulation) subjected, the carrier frequency being in the ultrasound range. After that will possibly a dynamic compression or dynamic error compensation (depending on the signal). Then another one follows Frequency response linearization and that then output signal is the Ultrasound transducer supplied.
- the circuit according to FIG. 2 differs from FIG. 1 essentially in that that instead of double sideband amplitude modulation, single sideband amplitude modulation is carried out, the carrier in the ultrasonic range about 12dB is suppressed.
- the level of the audible sound pressure depends on Sound pressure of the ultrasound signal, the non-linearity parameter of the medium Frequency of the resulting audio signal as well as the distance to the source and the Damping the medium.
- the differential frequency wave builds up with increasing Decency to the source. Due to the damping of the ultrasonic wave in the air the greatest sound pressure is reached at a certain distance until the level at distance increases due to damping.
- the damping of the Ultrasound in the air depends on the frequency. The higher the frequency is, the higher the absorption of the sound in air.
- an ideal frequency range from approx. 80 kHz to 180 kHz is specified can be.
- the frequency range is chosen high enough to be as possible to effectively generate a DFW and a sufficient frequency separation from the to ensure audible sound, but low enough that the attenuation does not have too much of an impact on audio sound through the air.
- Another criterion is the directional characteristic of the emitter. The higher the radiated frequency, the more The radiation is more directed.
- a higher frequency makes sense for the close range, because the absorption of air is in the near range of negligible size, while the dimensions of the Depending on the application, transducers are so small that a stronger directivity is not achieved by shaping the converter, but only by increasing the Ultrasonic frequency can be realized.
- the frequency shift of the low-frequency signal (speech, music, noises, Sounds) in the ultrasound range is done by an amplitude modulation. there creates a carrier signal and an upper and a lower sideband, which the contain modulated information.
- the carrier signal e.g. 200kHz
- the upper sideband radiated via a converter and superimposed in the air. Because of the nonlinear Behavior of the air creates a signal whose frequency is the difference from the Carrier and the sideband frequency corresponds. The higher the frequencies of the radiated tones with constant amplitude, the louder the resulting Difference tones.
- the sound pressure of the differential tones increases quadratically with the Differential frequency of the emitted ultrasound tones.
- Inadequacy in amplitude modulation permanent carrier amplitude
- the sound pressure of the difference frequencies results, among other things, from the product of the signals to be mixed.
- the carrier is emitted in full even in the case of a modulation pause, ie when there is no signal at the modulator.
- the high amplitude of the wearer means constant noise pollution for the ears and permanent electrical stress on the transducers.
- the carrier is continuously emitted and has a larger amplitude than the sideband, which is modulated in time with the low frequency. The following measures therefore make sense:
- Noise reduction can be achieved if the amplitude of the carrier is reduced e.g. through a filter or already partially in the modulator Carrier suppression, while increasing the amplitude of the upper sideband becomes. This reduces the continuous level and the relative level on the wearer related change in level by modulation larger.
- the lower sideband must be strongly suppressed in order to Prevent mixing of the two sidebands from each other, which is strong would cause distortion.
- the carrier amplitude is modulated with the amplitude of the signal to be transmitted, so no signal is emitted in the event of a pause in modulation. Then one is required additional controlled compressor stage that compensates for amplitude errors that result from the modulation of the carrier.
- the modulator output signal is hidden if none Input signal is present.
- the amplitude-modulated low-frequency vibration is associated with high sound pressure radiated from a converter.
- a difference frequency spectrum that corresponds to the spectrum of the low frequency.
- single sideband modulation is optimal. If the carrier at of an ordinary double sideband AM is partially suppressed Suppression of the lower sideband is essential because of the mixture of the two Sidebands cause additional differential frequencies, which change in shape of distortion noticeable.
- the modulation is therefore implemented either as a normal two-sideband AM or as a single sideband AM, in which the carrier is used for further function optimization about 12dB is suppressed.
- the relationship between the electrical input signal of the piezoelectric Converter and the sound pressure level of the differential tones is non-linear. With a Compensation circuit can achieve linear transmission.
- the Equalization can take place before the modulation in the low frequency range or after the Modulation in the ultrasound range. Equalization after modulation has the advantage that thereby the modulation reserve of the modulator when a Frequency range is not restricted.
- the difference sound wave arises in the emitted ultrasound cone.
- the cross section of the Kegels has an influence on the resulting audio frequency response.
- the audible signal is created at the interface that is held into the sound beam.
- the lower limit frequency depends on the cross-sectional area of the beam brought object.
- the maximum of the sound pressure results at a certain distance from the Source. It occurs at different intervals for different audio frequencies.
- a linear frequency response can therefore only for a certain distance set a special distance-related equalization.
- the signal processing must therefore have a special distance-dependent for a linear frequency response Frequency response equalization include.
- the arrangement of the transducers plays a role here: are the transducers on a plate arranged as close as possible, the bass reproduction of the loudspeaker is quieter than in an arrangement in which the same number of transducers are attached in a ring is.
- the described analog amplitude modulation can also be done digitally Multiplication of a sine wave (carrier) with a Low frequency signal, partial suppression of the carrier and suppression of the lower sideband are possible with a DSP module - Figure 3 -. Frequency response corrections can also be carried out relatively easily.
- the level of audio sound pressure depends, among other things. from the nonlinearity parameter of the Medium.
- a suitable medium between the ultrasound emitter and the receiver can be the sound pressure increase the audio signal.
- the audio sound pressure can be increased by another measure. conditioned due to the increasing division of the wavefront as it spreads is synonymous with the creation of harmonics. After an energy balance the energy contained in the harmonics is not available for the differential sound wave Available. In a way, there is an energy flow from the fundamental to Harmonics. If it is possible to slow down this flow of energy, then that would be possible Increase audio sound pressure.
- a sound-permeable medium contains small cavities, which together with the Material gives a variety of Heimholtz resonators.
- the resonators are on the the first harmonics of the signal and thereby slow down the energy flow higher harmonics. If the cavities are filled with a non-linear medium, e.g. a liquid, this measure allows a higher value for the Achieve nonlinearity parameters, which increases the sound pressure of the differential tones has been.
- This technology makes it possible to build reflectors that passively pass through Increase the sound pressure of the differential tones.
- the process combines low-frequency audio with strong Polar pattern of ultrasound.
- the directional characteristic of the speaker is almost independent of the signal frequency.
- the filter is not required for narrowband converters because the transfer function of the Converter is already equivalent to that of a narrow-band filter.
- the system must be tuned so that the carrier frequency is approximately at the -6dB point the filter edge comes to rest. Cutting the lower sideband causes a reduction in distortion.
- Temperature-dependent drift of the filter flank of narrowband converters and Filtering must be compensated for by tracking the carrier frequency.
- the carrier frequency is tracked as far as possible in signal pauses.
- the filter is to be designed in such a way that from the signal frequency of 1 kHz an attenuation of 3 dB / oct. he follows.
- the transducer dimensions exceed approximately 1 ⁇ 4 of the lowest low-frequency wavelength to be emitted, so occur in the near field of the transducer increasing distortion due to differences in transit time of the signals.
- the Dimensions of the transducer should therefore be smaller than the stated wavelength be dimensioned.
- An even more directed radiation of the audio tape can be achieve as follows:
- the sound pressure of the audio tape depends on the product of the sound pressure of the Carrier signal and the sideband. By increasing the sound pressure - either the carrier or the sideband - the resulting increases Sound pressure in the audio frequency range.
- the radiation of a broad Frequency range at high sound pressure poses certain difficulties.
- a special, very narrow-band, sensitive and very directional converter generates the carrier signal, while the sideband with a broadband Converter / converter array is superimposed. Since the sound pressure from the Product of the two ultrasound sound pressures to be superimposed can be over the sound pressure of the wearer within wide limits the sound pressure of the audio wave adjust and at the same time the level of the Reduce the ultrasound carrier. The superposition of sound waves and generation of mixed products, however, takes place only in the area where both sound waves equally fill the room. Because of the very strong possible Directional characteristics of the carrier radiator also result from this for the audio wave a very pronounced directivity.
- A is used to generate the audio signal from the modulated ultrasound signal certain distance required along which the wave is in the air demodulated. If the ultrasound has covered the required distance, then so causes a permeable for audio frequencies, but for ultrasound impermeable filter that the audio wave is clearly audible, the ultrasonic signal but is strongly dampened.
- the filter has on the directional characteristic of the converter no significant impact.
- the filter must be designed so that there are frequencies above the listening range heavily attenuated, while audio frequencies experience little attenuation. It is sensibly arranged at the end of the generation zone.
- the modulator contains one Circuit that fulfills this function.
- Moving the audio sound can also be done with a Running speed of the treadmill / escalator synchronized switching from ultrasound emitters located above the listener, which always only the areas of the room where the listener is moving.
- the method is a combination of the "phased array” technique and the one above described “ultrasonic speakers”.
- FIGS. 4a and 4b show the propagation of an audio sound wave that is generated by an ultrasound transducer.
- virtual audio sound sources virtual loudspeakers
- Small loudspeakers are mounted close to each other on a bar, all of which can emit audio sound as spherical emitters (FIG. 5) and which are controlled with the same audio signal with a time delay.
- the sound coming from the first loudspeaker is amplified by the second, etc.
- the large number of loudspeakers an infinite number of virtual sound sources arise in the ultrasound beam, which are switched on depending on the location with the duration of the sound, results in a very strong bundling of the audio sound.
- the audio sound in the ultrasound beam according to the invention arises in Ultrasound beam itself.
- the speaker becomes louder until the Ultrasound level has decreased so far that the non-linear effect of the air is not works more and therefore no more parts are added to the audio sound generation become.
- the length of the active zone of audio sound generation in the ultrasound beam determines the lower limit frequency of the directional audio sound source. To have to there should be at least as many virtual sound sources as the active zone is several wavelengths long at the lower cutoff frequency. Therefore require Audio frequencies below 100 Hz large distances between the listener and the ultrasound emitter (and thus also high output powers). Use offers a solution psychoacoustic signal processing as described above.
- the level and the lower Playback frequency of the audio signal are location-dependent.
- the one to generate the Audio ultrasound levels which are in principle necessary, only have to be in the active zone of the ultrasound beam. Is the directional audio sound beam first generated, you can the ultrasound portion with an acoustic low-pass filter Eliminate (ultrasound absorber permeable to sound).
- FIGS. 6a and 6b show typical application examples of the ultrasound emitter, which is arranged under a ceiling and which are modulated with audio signals Directs ultrasound rays to a wall, one of which is ultrasound absorbing Coating (ultrasound reflection coating) aligned so that ultrasound absorbs will have. The then reflected audio signals are free from ultrasound and can be transmitted from the People are heard in front of the wall.
- Coating ultrasound reflection coating
- Ultrasonic film transducers are also particularly suitable of a capacitor (electret) converter a foil and one accordingly (with grooves or holes) formed counter electrode.
- the embodiment variant is also advantageous, in which a Distance measuring device to an ultrasonic measuring device is determined where there is a listener to be sonicated. If this is in a critical area Ultrasound beam, which could be harmful to health, will Ultrasound playback is switched off so that the respective person (or the animal) is not exposed to high ultrasound levels. If the ultrasound is on you certain area should be directed and if this area is still moved (this is the case, for example, with a single listener who is on a Stage should be moved and sonicated) so it is advantageous if one Device is designed by means of which the listener to be sounded is currently localized can be, so that the sound is then preferably only on the localized Area.
- the sonic listener carries a transmitter with navigation (e.g. GPS) and thus constantly its own navigation data to a receiving device which in turn sends to control the pivoting of the ultrasound beam is used.
- the listener to be sounded could also use a so-called TAG identifier, its exact position from a corresponding one Interogator (query unit for the TAG) is determined, with which then in turn the pivoting of the ultrasound beams is controlled.
- TAG identifier so-called TAG identifier, its exact position from a corresponding one Interogator (query unit for the TAG) is determined, with which then in turn the pivoting of the ultrasound beams is controlled.
- Such applications are particularly advantageous in a theater (for the prompter) or also in the television studio at a TV show, when it’s over the stage moving moderator should receive instructions that are not for the rest of the audience should be audible.
- the panning of the ultrasound beam can be done with that in this application Descriptive different techniques take place, that is, by pivoting the Ultrasound emitter or through a swiveling reflector or through the So-called "phased array” control, the ultrasound beams is determined electronically.
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- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Health & Medical Sciences (AREA)
- Audiology, Speech & Language Pathology (AREA)
- General Health & Medical Sciences (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Circuit For Audible Band Transducer (AREA)
- Transducers For Ultrasonic Waves (AREA)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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DE19919980 | 1999-04-30 | ||
DE19919980 | 1999-04-30 | ||
EP00925256A EP1175812B1 (fr) | 1999-04-30 | 2000-05-02 | Procede de reproduction de son audio a l'aide de haut-parleurs a ultrasons |
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EP00925256A Division EP1175812B1 (fr) | 1999-04-30 | 2000-05-02 | Procede de reproduction de son audio a l'aide de haut-parleurs a ultrasons |
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EP1484944A2 true EP1484944A2 (fr) | 2004-12-08 |
EP1484944A3 EP1484944A3 (fr) | 2004-12-15 |
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EP04021692A Withdrawn EP1484944A3 (fr) | 1999-04-30 | 2000-05-02 | Procédé de reproduction d'un signal audio avec un haut-parleur ultrasonore |
EP00925256A Expired - Lifetime EP1175812B1 (fr) | 1999-04-30 | 2000-05-02 | Procede de reproduction de son audio a l'aide de haut-parleurs a ultrasons |
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Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP00925256A Expired - Lifetime EP1175812B1 (fr) | 1999-04-30 | 2000-05-02 | Procede de reproduction de son audio a l'aide de haut-parleurs a ultrasons |
Country Status (6)
Country | Link |
---|---|
US (1) | US20050207590A1 (fr) |
EP (2) | EP1484944A3 (fr) |
AT (1) | ATE276636T1 (fr) |
AU (1) | AU4403600A (fr) |
DE (1) | DE50007789D1 (fr) |
WO (1) | WO2001008449A1 (fr) |
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- 2000-05-02 EP EP04021692A patent/EP1484944A3/fr not_active Withdrawn
- 2000-05-02 DE DE50007789T patent/DE50007789D1/de not_active Expired - Lifetime
- 2000-05-02 AT AT00925256T patent/ATE276636T1/de not_active IP Right Cessation
- 2000-05-02 EP EP00925256A patent/EP1175812B1/fr not_active Expired - Lifetime
- 2000-05-02 AU AU44036/00A patent/AU4403600A/en not_active Abandoned
- 2000-05-02 WO PCT/EP2000/003931 patent/WO2001008449A1/fr active IP Right Grant
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US5095509A (en) * | 1990-08-31 | 1992-03-10 | Volk William D | Audio reproduction utilizing a bilevel switching speaker drive signal |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2109328A1 (fr) | 2008-04-09 | 2009-10-14 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Appareil pour le traitement d'un signal audio |
US9191743B2 (en) | 2008-04-09 | 2015-11-17 | Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. | Apparatus using missing fundamental frequencies to improve loudspeaker sound focusing |
DE102017211923A1 (de) * | 2017-07-12 | 2019-02-07 | Zf Friedrichshafen Ag | Lokalisierte Informationsausgabe |
Also Published As
Publication number | Publication date |
---|---|
EP1175812A1 (fr) | 2002-01-30 |
EP1175812B1 (fr) | 2004-09-15 |
DE50007789D1 (de) | 2004-10-21 |
AU4403600A (en) | 2001-02-13 |
EP1484944A3 (fr) | 2004-12-15 |
ATE276636T1 (de) | 2004-10-15 |
WO2001008449A1 (fr) | 2001-02-01 |
US20050207590A1 (en) | 2005-09-22 |
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