CN101014209B - Full band natural sound effect audio directional loudspeaker - Google Patents
Full band natural sound effect audio directional loudspeaker Download PDFInfo
- Publication number
- CN101014209B CN101014209B CN2007100482998A CN200710048299A CN101014209B CN 101014209 B CN101014209 B CN 101014209B CN 2007100482998 A CN2007100482998 A CN 2007100482998A CN 200710048299 A CN200710048299 A CN 200710048299A CN 101014209 B CN101014209 B CN 101014209B
- Authority
- CN
- China
- Prior art keywords
- signal
- frequency
- output
- transducer
- audio
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Circuit For Audible Band Transducer (AREA)
- Stereophonic System (AREA)
Abstract
The invention relates to one whole frequency band natural audio direction microphone, which comprises low pass filter, AD converter, signal process system, signal back process system and power amplifier, DA conversion set, re-set filter sets and energy conversion, wherein, the above signal process system comprises more than three frequency division digital filter and more than three filters with inclination and supersonic modulation. The invention can compensate audio signals in whole frequency band range for natural audio effect program to realize whole frequency output.
Description
Technical field
The present invention relates to a kind of audio directional loudspeaker, particularly can bring the loud speaker that line frequency compensated and carried out the high directivity of natural sound effect processing into the audio frequency full range.
Background technology
Audio directional loudspeaker is a kind of a kind of New-type loudspeaker that utilizes the aerial nonlinear propagation effects of ultrasonic wave to produce the high directivity audible sound.Audio signal is through forming the ultrasonic wave that contains this audio signal information after the signal processing, audible device by audio directional loudspeaker---transducer is transmitted into this ultrasonic wave in the air, this ultrasonic wave can demodulate the audio signal that it contains certainly in air then, forms one and has the very audio signal of highly directive.
Nineteen sixty-five, H.0.Berktay, a kind of more accurate parametric array theoretical model of parametric array theory that proposed in 1963 than the physics professor PeterWestervelt of Brown University has been proposed, having disclosed audio directional loudspeaker utilizes the conditioning of explaining by oneself of nonlinear propagation effects of ultrasonic generation high directivity audible sound to discuss model: the ultrasonic wave that contains audio signal information is proportional to ultrasonic signal envelope E (t) square the secondary time-derivative that transducer sends from the amplitude of the audio signal acoustic pressure P (t) that demodulates, promptly
According to this theory, can predict that existing audio directional loudspeaker signal processing method all can bring the frequency response of 12dB/ octave to tilt.Signal frequency is high more, its frequency domain amplitude response is big more, the 1kHz, the 2kHz signal that are identical amplitude are imported audio directional loudspeaker simultaneously, at last will be than the little 12dB of 2kHz audio signal in air from demodulating the 1kHz audio signal that comes, and this is in the distortion that has objectively caused signal.For this reason, various signal processing methods all will tilt to compensate to this frequency response, but brought a prominent question thus: if about 20kHz bandwidth that whole audio signal is related to all compensates, dynamic compensation scope in whole frequency will be above 120dB, and this all can bring the difficulty that is difficult to realize on signal algorithm realization, transducer designs.
In addition, the sound wave that conventional loudspeakers is sent will arrive the audience in the different time to each direction of propagation propagation and from all directions, and this time-dependent is in the sonic propagation distance from the sound source to audience.Wherein the sound wave of directly propagating to the audience is called direct sound wave, and it has arrived and controlled the sensation of audience to sound position, size and sound source character the earliest.Next be some spatially closer echoes, be called early reflection, it is that the reflection to sound wave on all directions produces by room or other barrier, and the time that arrives the audience is indefinite.Early reflection provides the information about room-size, barrier distance for the audience.After these early reflections, because repeatedly reflection, increasing intensive reflection will arrive the audience, and these reflection groups are considered to reverberation.Therefore, to offer audience's sound will be the synthetic sound of direct sound wave, reflection and reverberation sound to conventional loudspeakers.Compare with conventional loudspeakers, the sound that audio directional loudspeaker produces is only propagated along a direction owing to have very high directive property, therefore, the sound that arrives the audience has only direct sound wave, and reflection, reverberation sound are very faint or do not have substantially, thereby makes its sound sound nature.
Summary of the invention
The purpose of this invention is to provide and a kind ofly can compensate and carry out the full band natural sound effect audio directional loudspeaker that natural sound effect is handled in full range band scope, to solve because the frequency response of 12dB/ octave tilts to be difficult to realize that the low-frequency band or the high-frequency band signals frequency domain response of the audio directional loudspeaker output that the full bandwidth compensation causes weaken, problem of dtmf distortion DTMF.
Another object of the present invention provides a kind of equipment that produces the synthetic natural sound of high directivity direct sound wave, reflection and reverberation sound, solve audio directional loudspeaker and produce high directivity sound, do not have or have only very little reflection, reverberation sound and the sound that causes sounds factitious problem owing to have only direct sound wave.
The objective of the invention is to be realized by the following technical programs: a kind of full band natural sound effect audio directional loudspeaker comprises:
Low pass filter carries out Filtering Processing to the audio signal of input, in order to the outer composition of the band of filtering 0～20KHz audio signal;
AD converter is connected with the low pass filter output, in order to simulated audio signal is converted to digital signal;
Signal processing system comprises:
The branch frequency band digital filter that (contains three, together following) more than three, the audiorange of the audio signal that AD converter is next is divided into divides frequency band more than three, respectively it is carried out filtering;
The filter of having more than three-12dB/ octave frequency response carries out frequency compensation respectively to the above-mentioned minute next signal of frequency band digital filter;
One or more ultrasonic modulators carry out ultrasonic modulation treatment to the signal after the frequency compensation;
Signal post-processing system and power amplifier, whether above-mentioned signal after ultrasonic modulation treatment is outputed to each signalling channel according to it carry out different processing: as take to enter into a plurality of output channels, then direct sound wave, reflection, reverberation sound separate processes; If do not output to a plurality of passages, then direct-connected sound, reflection, reverberation sound will be done synthetic the processing; Signal after the processing is again through pressing the output of multichannel or single channel after the power amplification;
The DA converter bank is in order to be converted to analog signal with the digital signal according to single channel or multichannel output after the above-mentioned power amplification;
The reconstruction filter group causes the rough high-frequency signal composition of signal in order to filtering from the analog signal that the DA converter bank is come, make analog signal become level and smooth;
Transducer group, the electrical signal conversion that is used for the output of reconstruction filter group is an acoustical signal, and output contains the high directivity ultrasonic signal of audio signal modulation.
Also have in the above-mentioned signal post-processing system: delayer, carry out delay process to the signal after the frequency compensation, with output early reflection acoustical signal; Reverberator carries out reverberation again to the signal of frequency compensation after to delay process and handles, with output reverberation sound signal.
The present invention be utilize ultrasonic wave high directivity characteristics and it in air non-linear relay from demodulating the principle of high directivity audible sound, and a kind of audio directional loudspeaker of making.Compare with conventional loudspeakers, this is first kind can realize simultaneously that the audio frequency communication space distributes and the loud speaker of sound source position control.
At present because the frequency response of 12dB/ octave tilts to be difficult in the full range band compensates, therefore generally all adopt the method and apparatus that low-frequency band or high frequency band are not compensated to carry out product design.The present invention proposes a kind of method and apparatus of full range being brought into the line frequency compensation.
Substantially has only direct sound wave (because this loud speaker has the high directivity characteristics in the present audio directional loudspeaker research, run into the reflected sound that barrier such as wall produces and also have very strong directive property, therefore reflection, reverberation sound does not have substantially or very faint), this sounds not too natural (our experiment confirm this point) with regard to the sound that causes present audio directional loudspeaker.The natural sound effect treatment facility that the present invention proposes (can realize that also available software realizes with hardware) sounds factitious problem with the sound that the realization approach has solved existing audio directional loudspeaker.
The invention has the advantages that the mode that can utilize software program, hardware realization or software to cooperate with hardware realizes the output of full range band audio frequency flexibly, the voice packet of its output contains direct sound wave, reflection and reverberation sound, has the natural sound effect effect.
Description of drawings
Fig. 1 shows full range band audio directional loudspeaker general structure.
Fig. 2 shows the transducer portion structure.
Fig. 3 shows the natural sound effect implementation method.
Fig. 4 shows multichannel, single transducer natural sound effect audio directional loudspeaker structure.
Fig. 5 is a typical signal processing realization flow.
Embodiment
Fig. 1 shows the hardware schematic structure of full range band audio directional loudspeaker.Full range band audio directional loudspeaker is made of low pass filter 1, AD converter 2, signal processing system 3, signal post-processing system and power amplifier 4, DA converter bank 5, signal reconstruction bank of filters 6 and transducer group 7.Audio directional loudspeaker is a low pass filter 1 with extraneous first main devices that contacts.Audio signal is passed through the outer composition of band of low pass filter 1 filtering audio signal, and is input in the audio-frequency directional loudspeaker system.The audio signal of the outer composition of filtering voiced band is in 20Hz ~ 20kHz or the 0 ~ 20kHz scope, is converted into digital signal by AD converter 2.The signal processing system that is positioned at after the AD converter 2 can be made of single-chip microcomputer, signal processing chip (DSP) or field programmable gate device (FPGA), it will be handled the digital signal of AD converter 2 inputs, and the signal after will handling is sent into signal post-processing system and power amplifier 4.Signal post-processing system and power amplifier 4 can be made of signal processing chip (DSP) or field programmable gate array (FPGA)+D class, E class or T power-like amplifier.Signal processing system is divided into limited several frequency bands with signal, and carries out the correspondent frequency compensation according to the characteristic of different frequency bands, and the signal post-processing system provides time-delay, reverberation processing and power amplification.And will delay time, direct sound wave, reflection, the reverberation sound signal or be synthesized to of reverberation after handling output on the transducer together, perhaps outputs to respectively on three transducers, perhaps carry out combination in any and output on the transducer of combination in any.
After this, export along separate routes according to the principle of high-frequency band signals input high frequency band output channel, midband signal input midband output channel, low band signal input low-frequency band output channel.The concrete condition of the visual transducer group frequency response of the division of this frequency band is carried out flexibly.Signal as 1 couple of 0 ~ 500Hz of transducer has frequency response preferably, then can tell the low band signal of one tunnel 0 ~ 500Hz and handle frequency band and output channel, and the rest may be inferred by analogy.After signal post-processing system and power amplifier 4, form DA converter bank 5, form bank of filters 6, form transducer group 7 by n transducer by n signal reconstruction filter by n DA transducer.Be the 1st output channel when n=1, this passage is made up of DA transducer 1, signal reconstruction filter 1, transducer 1.The rest may be inferred by analogy, is the 2nd output channel when n=2, is the n output channel when n=n.In these passages, the DA transducer is used for digital signal is converted to analog signal, and reconstruction filter is used for the outer radio-frequency component of the unwanted band of filtered signal, and it is acoustical signal that transducer then is used for electrical signal conversion.Because each passage all is to design for different frequency bands, have the frequency response characteristic best to this band signal, and all the shared frequency band of passage will cover the required whole frequency band ranges of audio directional loudspeaker altogether, therefore, the audio-frequency directional loudspeaker system with full range band good frequency response characteristic can be accomplished by this method and apparatus.
Fig. 2 shows the concrete arrangement of transducer group 7.Transducer group can be arranged on the plane, also can adopt the spatial arrangement mode.Transducer group can be divided into low-frequency transducer 8, intermediate frequency transducer 9 and high-frequency transducer 10 3 classes substantially, and every class can require to adopt the transducer of a plurality of frequency bands to make up according to concrete frequency band again.Transducer for identical frequency band can have the transducer more than 1 or 1 to carry out signal output.
Fig. 3 shows the natural sound effect method for processing signals.The early reflection signal is directly produced by delayed time system 11, and reverb signal then is after by delayed time system 11 signal being carried out delay process, delivers to and carries out in the reverberation system 12 producing after reverberation is handled.Direct sound wave signal, early reflection acoustical signal, the reverberation sound signal that system produces lumps together and just formed the natural sound effect acoustical signal of handling through natural sound effect.Natural sound effect signal processing method shown in Figure 3 can be finished by signal processing system 3 softwares, also can be finished by signal post-processing system and power amplifier 4 hardware.Direct sound wave, reflection, reverberation sound can be synthesized to and output to a transducer together, also they can be outputed to respectively on three different transducers, or they are carried out combination in any output on the transducer of combination in any.Signal after handling by natural sound effect signal processing method shown in Figure 3 is after audio directional loudspeaker is transmitted in the air, high directivity will be produced, the audio signal that includes direct sound wave, pseudo-reflection, pseudo-reverberation sound makes sound that the audience hears naturally.
Audio directional loudspeaker structure chart when Fig. 4 shows transducer group 7 and has only a transducer.Can not fully guarantee the good response of the full range band signal frequency domain of audio directional loudspeaker this moment, but can realize the generation of natural sound effect high directivity sound signal.
Fig. 5 shows a typical signal processing realization flow.Audio signal is input in the program through AD converter 2 samplings.This input audio signal is divided into several limited band signals by digital filter.Be not uniformly-spaced to divide during frequency band division, but divide when when low frequency, dividing closeer, high frequency thinner.Typically be divided into 0 ~ 500Hz as one, 500Hz ~ 4kHz, 4kHz ~ 20kHz, the former adopts lowpass digital filter to leach, and the latter two adopt bandpass digital filters to leach.To carry out frequency compensation respectively to these ready-portioned band signals after having divided frequency band.Its implementation is to adopt filter design method such as FIR such as ripple such as Parks-McClellan optimizations grade to design one respectively at each frequency band to have-the FIR filter of 12dB/ octave frequency response, allow these band signals by these filters then respectively, thereby realize the frequency domain compensation of each band signal.Signal after compensation will no longer include the frequency ramps response of 12dB/ octave.Signal after the frequency response compensation carries out ultrasonic modulation treatment respectively through corresponding ultrasonic modulator and is converted in the ultrasonic range from audiorange.Enter the natural sound effect handling procedure then.The natural sound effect handling procedure will carry out delay process to signal, reverberation is handled.Whether the signal after natural sound effect is handled outputs to a plurality of signalling channels according to it is carried out different processing: if pass in and out a plurality of output channels, then direct sound wave, reflection, reverberation sound do not mix, separate processes; If do not output to a plurality of passages, then direct sound wave, reflection, reverberation sound will be done synthetic the processing.Signal through after the above-mentioned processing will output to respectively in the corresponding output channel according to its frequency band of living in, promptly realize the output of signal multichannel or single channel.Above signal processing will carry out again and again, up to EP (end of program).
Claims (7)
1. full band natural sound effect audio directional loudspeaker comprises:
Low pass filter carries out Filtering Processing to the audio signal of input, in order to the outer composition of the band of filtering 20Hz～20KHz or 0～20KHz audio signal;
AD converter is connected with the low pass filter output, in order to simulated audio signal is converted to digital signal;
Signal processing system comprises:
Branch frequency band digital filter more than three, the audiorange of the audio signal that AD converter is next is divided into more than three divides frequency band, respectively it is carried out filtering;
The filter that having more than three-12dB/ octave frequency response is tilted carries out frequency compensation respectively to the above-mentioned minute next signal of frequency band digital filter;
One or more ultrasonic modulators carry out ultrasonic modulation treatment to the signal after the frequency compensation;
Signal post-processing system and power amplifier, whether above-mentioned signal after ultrasonic modulation treatment is outputed to each signalling channel according to it carry out different processing: as take to enter into a plurality of output channels, then direct sound wave, reflection, reverberation sound separate processes; If do not output to a plurality of passages, then direct sound wave, reflection, reverberation sound will be done synthetic the processing; Signal after the processing is again through pressing the output of multichannel or single channel after the power amplification;
The DA converter bank is in order to be converted to analog signal with the digital signal according to single channel or multichannel output after the above-mentioned power amplification;
The reconstruction filter group causes the rough high-frequency signal composition of signal in order to filtering from the analog signal that the DA converter bank is come, make analog signal become level and smooth;
Transducer group, the electrical signal conversion that is used for the output of reconstruction filter group is an acoustical signal, and output contains the high directivity ultrasonic signal of audio signal modulation.
2. according to the described full band natural sound effect audio directional loudspeaker of claim 1, it is characterized in that: described transducer group is divided into low-frequency transducer, intermediate frequency transducer and high-frequency transducer three classes, every class requires to adopt the transducer of a plurality of frequency bands to make up according to concrete frequency band, and has the transducer more than 1 or 1 to carry out signal output for the transducer of identical frequency band.
3. according to the described full band natural sound effect audio directional loudspeaker of claim 2, it is characterized in that: described a plurality of transducers can be arranged on the plane, also can adopt the spatial arrangement mode.
4. according to the described full band natural sound effect audio directional loudspeaker of claim 1, it is characterized in that: described signal processing system is divided into 0～500Hz, 500Hz～4kHz, three branch frequency bands of 4kHz～20kHz with the audio signal typical case, the former adopts lowpass digital filter to leach, and the latter two adopt bandpass digital filter to leach.
5. according to the described full band natural sound effect audio directional loudspeaker of claim 1, it is characterized in that: described signal processing system adopts has-and filter that the frequency response of 12dB/ octave is tilted is a filter such as FIR such as ripple such as Parks-McClellan optimizations grade.
6. according to the described full band natural sound effect audio directional loudspeaker of claim 1, it is characterized in that: described signal processing system is by single-chip microcomputer, and signal processing chip DSP and programmable gate array FPGA constitute; Signal post-processing system and power amplifier by signal processing chip DSP and programmable gate array FPGA+D class, E class or T power-like amplifier form.
7. according to the described full band natural sound effect audio directional loudspeaker of the arbitrary claim of claim 1-6, it is characterized in that: also have in the described signal post-processing system:
Delayer carries out delay process to the signal after the ultrasonic modulation treatment, with output early reflection acoustical signal;
Reverberator carries out reverberation again to the signal after the delay process and handles, with output reverberation sound signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2007100482998A CN101014209B (en) | 2007-01-19 | 2007-01-19 | Full band natural sound effect audio directional loudspeaker |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2007100482998A CN101014209B (en) | 2007-01-19 | 2007-01-19 | Full band natural sound effect audio directional loudspeaker |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101014209A CN101014209A (en) | 2007-08-08 |
| CN101014209B true CN101014209B (en) | 2011-06-01 |
Family
ID=38701440
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2007100482998A Active CN101014209B (en) | 2007-01-19 | 2007-01-19 | Full band natural sound effect audio directional loudspeaker |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN101014209B (en) |
Families Citing this family (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9425747B2 (en) | 2008-03-03 | 2016-08-23 | Qualcomm Incorporated | System and method of reducing power consumption for audio playback |
| CN101577534B (en) * | 2009-03-13 | 2012-01-04 | 福建三元达通讯股份有限公司 | Digital filtering frequency self-compensation circuit |
| US8189802B2 (en) * | 2009-03-19 | 2012-05-29 | Qualcomm Incorporated | Digital filtering in a Class D amplifier system to reduce noise fold over |
| CN101719368B (en) * | 2009-11-04 | 2011-12-07 | 中国科学院声学研究所 | Device for directionally emitting sound wave with high sound intensity |
| CN101820564A (en) * | 2010-03-16 | 2010-09-01 | 电子科技大学 | Minitype multichannel audio frequency directional loudspeaker |
| US8717211B2 (en) | 2010-11-30 | 2014-05-06 | Qualcomm Incorporated | Adaptive gain adjustment system |
| CN102098610B (en) * | 2011-03-11 | 2015-10-21 | 湖南继善高科技有限公司 | Loudspeaker unit, loudspeaker arrangement and directed sound wave scarer |
| CN103826185B (en) * | 2014-03-07 | 2017-02-08 | 深圳市晶科源科技有限公司 | Natural sound effect processing circuit |
| CN104661153B (en) * | 2014-12-31 | 2018-02-02 | 歌尔股份有限公司 | A kind of compensation method of earphone audio, device and earphone |
| CN105120402A (en) * | 2015-08-21 | 2015-12-02 | 电子科技大学 | Directional audio frequency exciting system |
| CN105554548A (en) * | 2015-12-08 | 2016-05-04 | 深圳Tcl数字技术有限公司 | Audio data output method and device |
| CN105635901A (en) * | 2016-03-16 | 2016-06-01 | 朱丽芬 | High-fidelity bluetooth sound equipment |
| CN105681938A (en) * | 2016-03-16 | 2016-06-15 | 朱丽芬 | High-sound-quality Bluetooth loudspeaker box |
| RU2020112255A (en) * | 2017-10-20 | 2021-09-27 | Сони Корпорейшн | DEVICE FOR SIGNAL PROCESSING, SIGNAL PROCESSING METHOD AND PROGRAM |
| CN108696797A (en) * | 2018-05-17 | 2018-10-23 | 四川湖山电器股份有限公司 | A kind of audio electrical signal carries out frequency dividing and synthetic method |
| CN110401901A (en) * | 2019-08-22 | 2019-11-01 | 杭州聚声科技有限公司 | A kind of parametric array sonification system |
| CN111530722A (en) * | 2020-04-21 | 2020-08-14 | 民航成都电子技术有限责任公司 | Ultrasonic transducer, directional sound wave bird repelling system and method |
| CN112153535B (en) * | 2020-09-03 | 2022-04-08 | Oppo广东移动通信有限公司 | Sound field expansion method, circuit, electronic equipment and storage medium |
| CN113473311A (en) * | 2021-07-01 | 2021-10-01 | 中汽研（天津）汽车工程研究院有限公司 | In-vehicle multimedia sound zone control device and method |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1596037A (en) * | 2004-07-14 | 2005-03-16 | 华南理工大学 | Signal processing method for three-loudspeaker virtual 5.1 channel surround sound |
-
2007
- 2007-01-19 CN CN2007100482998A patent/CN101014209B/en active Active
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1596037A (en) * | 2004-07-14 | 2005-03-16 | 华南理工大学 | Signal processing method for three-loudspeaker virtual 5.1 channel surround sound |
Also Published As
| Publication number | Publication date |
|---|---|
| CN101014209A (en) | 2007-08-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN101014209B (en) | Full band natural sound effect audio directional loudspeaker | |
| Boone et al. | Spatial sound-field reproduction by wave-field synthesis | |
| WO2014069111A1 (en) | Signal processing device, signal processing method, measurement method, and measurement device | |
| WO2006009028A1 (en) | Sound reproducing device and sound reproducing system | |
| EP1341399A3 (en) | Sound field control method and sound field control system | |
| EP3214620A1 (en) | A monaural intrusive speech intelligibility predictor unit, a hearing aid system | |
| CN105874820A (en) | Generating binaural audio in response to multi-channel audio using at least one feedback delay network | |
| CN101790118A (en) | Audio-frequency directional loudspeaker system and signal processing method thereof | |
| CN106210983A (en) | A kind of realize the method for Kara OK function, device and earphone by earphone | |
| US10127005B2 (en) | Mobile cluster-based audio adjusting method and apparatus | |
| JP2013247477A5 (en) | Sound processing apparatus and sound processing method | |
| CN107948898A (en) | A kind of hearing aid auxiliary tests match system and method | |
| US4672569A (en) | Method and apparatus for simulating outer ear free field transfer function | |
| CN102592606B (en) | Isostatic signal processing method for compensating small-space audition acoustical environment | |
| CN109640229A (en) | A kind of method reducing directional loudspeaker noise and the directional loudspeaker for reducing noise | |
| CN106714040B (en) | A kind of digital variable reverberant audio system and its implementation | |
| CN2938669Y (en) | Bass processing circuit | |
| JPH08271627A (en) | Distance measuring device between loudspeaker and microphone | |
| CN209642950U (en) | A kind of directional loudspeaker reducing noise | |
| JP2688051B2 (en) | Broadcast space limiting device | |
| CN102163426B (en) | Fixed point transmission system | |
| Coker et al. | A survey on virtual bass enhancement for active noise cancelling headphones | |
| De Vries et al. | Auralization of room acoustics by wave field synthesis based on array measurements of impulse responses | |
| Nomura et al. | Speech intelligibility and modulation transfer function in non-exponential decay fields | |
| JP2000032597A (en) | Hearing aid system using directivity microphone array |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant |