System and method for digital signal processing

Information

  • Patent Grant
  • 10917722
  • Patent Number
    10,917,722
  • Date Filed
    Tuesday, June 4, 2019
    5 years ago
  • Date Issued
    Tuesday, February 9, 2021
    3 years ago
Abstract
A system and method for digital processing including a gain element to process an input audio signal, a high pass filter to then filter the signal and create a high pass signal, a first filter module to filter the high pass signal and create a first filtered signal and a splitter to split the high pass signal into two high pass signals. The first filter module filters one high pass signals before a first compressor modulates the signal or a high pass signal to create a modulated signal. A second filter module filters the modulated signal to create a second filtered signal that is processed by a first processing module including a band splitter that splits the signal into low and high band signals that are then modulated by compressors. A second processing module processes the modulated low and high band signals to create an output signal.
Description
BACKGROUND OF THE INVENTION
Field of the Invention

The present invention provides for methods and systems for digitally processing an audio signal. Specifically, some embodiments relate to digitally processing an audio signal in order to deliver studio-quality sound in a variety of consumer electronic devices.


Description of the Related Art

Historically, studio-quality sound, which can best be described as the full reproduction of the complete range of audio frequencies that are utilized during the studio recording process, has only been able to be achieved, appropriately, in audio recording studios. Studio-quality sound is characterized by the level of clarity and brightness which is attained only when the upper-mid frequency ranges are effectively manipulated and reproduced. While the technical underpinnings of studio-quality sound can be fully appreciated only by experienced record producers, the average listener can easily hear the difference that studio-quality sound makes.


While various attempts have been made to reproduce studio-quality sound outside of the recording studio, those attempts have come at tremendous expense (usually resulting from advanced speaker design, costly hardware, and increased power amplification) and have achieved only mixed results. Thus, there exists a need for a process whereby studio-quality sound can be reproduced outside of the studio with consistent, high quality results at a low cost. There exists a further need for audio devices embodying such a process in the form of computer chips embedded within audio devices, or within processing devices separate and standalone from the audio devices. There also exists a need for the ability to produce studio-quality sound through inexpensive speakers, as well as through a variety of readily available consumer devices capable of reproducing sound, in both hardware-based and software-based embodiments.


SUMMARY OF THE INVENTION

The present invention meets the existing needs described above by providing for a system and method of digitally processing an audio signal in a manner such that studio-quality sound can be reproduced across the entire spectrum of audio devices. The present invention also provides for the ability to enhance audio in real-time and tailors the enhancement to the audio signal of a given audio device or delivery system and playback environment.


The present invention may provide for a computer chip that can digitally process an audio signal in such a manner, as well as provide for audio devices that comprise such a chip or equivalent circuit combination. The present invention may also provide for computer software readable and executable by a computer to digitally process an audio signal. In the software embodiments, the present invention may utilize existing hardware and software components on computers such as PCs, Mac, and mobile devices, comprising various operating systems such as Android, iOS, and Windows.


Accordingly, in initially broad terms, an audio input signal is first filtered with a high pass filter. In at least one embodiment, the input audio signal is processed with a first gain element. In at least one embodiment the first gain signal is then filtered with the high pass filter. The high pass filter, in at least one embodiment, is configured to remove ultra-low frequency content from the input audio signal resulting in the generation of a high pass signal.


In at least one embodiment, the high pass signal from the high pass filter is then filtered through a first filter module to create a first filtered signal. The first filter module is configured to selectively boost and/or attenuate the gain of select frequency ranges in an audio signal, such as the high pass signal.


In at least one embodiment, the first filter module boosts frequencies above a first frequency, and attenuates frequencies below a first frequency. In at least one embodiment, the high pass signal from the high pass filter is then split into a first high pass signal and a second high pass signal.


In at least one embodiment, the first filtered signal from the first filter module is then modulated with a first compressor to create a modulated signal. In at least one embodiment, the second high pass signal is then filtered through a first filter module to create a first filtered signal. In at least one embodiment, the first high pass signal is then modulated with a first compressor to create a modulated signal. The first compressor is configured for the dynamic range compression of a signal, such as the first filtered signal. Because the first filtered signal boosted higher frequencies and attenuated lower frequencies, the first compressor may, in at least one embodiment, be configured to trigger and adjust the higher frequency material, while remaining relatively insensitive to lower frequency material.


In at least one embodiment, the modulated signal from the first compressor is then filtered through a second filter module to create a second filtered signal. The second filter module is configured to selectively boost and/or attenuate the gain of select frequency ranges in an audio signal, such as the modulated signal. In at least one embodiment, the second filter module is configured to be in an at least partially inverse relation to the first filter module. For example, if the first filter module boosted content above a first frequency by +X dB and attenuated content below a first frequency by −Y dB, the second filter module may then attenuate the content above the first frequency by −X dB, and boost the content below the first frequency by +Y dB. In other words, the purpose of the second filter module in one embodiment may be to “undo” the gain adjustment that was applied by the first filter module.


In at least one embodiment, the second filtered signal from the second filter module is then processed with a first processing module to create a processed signal. In at least one embodiment, the modulated signal from the first compressor is then processed with a first processing module to create a processed signal. In at least one embodiment, the first processing module may comprise a peak/dip module. In other embodiments, the first processing module may comprise both a peak/dip module and a first gain element. The first gain element may be configured to adjust the gain of the signal, such as the second filtered signal. The peak/dip module may be configured to shape the signal, such as to increase or decrease overshoots or undershoots in the signal.


The processed signal from the first processing module is then split with a band splitter into at least low band signal and a high band signal. In at least one embodiment, each band may comprise the output of a fourth order section, which may be realized as the cascade of second order biquad filters.


The low band signal is modulated with a low band compressor to create a modulated low band signal, and the high band signal is modulated with a high band compressor to create a modulated high band signal. The low band compressor and high band compressor are each configured to dynamically adjust the gain of a signal. Each of the low band compressor and high band compressor may be computationally and/or configured identically as the first compressor.


At least the modulated low band signal and the modulated high band signal are then processed with a second processing module. The second processing module may comprise a summing module configured to combine the signals. The summing module in at least one embodiment may individually alter the gain of at least each of the modulated low band, and modulated high band signals. The second processing module may further comprise a second gain element. The second gain element may adjust the gain of the combined signal in order to create an output signal.


These and other objects, features and advantages of the present invention will become clearer when the drawings as well as the detailed description are taken into consideration.





BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature of the present invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:



FIGS. 1A and 1B illustrate schematics of several embodiments of the present invention directed to systems for digitally processing an audio signal.



FIGS. 2A, 2B, 2C, and 2D illustrate schematics of several other embodiments of the present invention directed to systems for digitally processing an audio signal.



FIGS. 3A, 3B, 3C, and 3D illustrate block diagrams of several other embodiments of the present invention directed to methods for digitally processing an audio signal.



FIGS. 4A, 4B, 4C, and 4D illustrate block diagrams of several other embodiment of the present invention directed to methods for digitally processing an audio signal.





Like reference numerals refer to like parts throughout the several views of the drawings.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As illustrated by the accompanying drawings, the present invention is directed to systems and methods for digitally processing an audio signal. Specifically, some embodiments relate to digitally processing an audio signal in order to deliver studio-quality sound in a variety of different consumer electronic devices.


As schematically represented, FIGS. 1A, 1B, 1C, and 1D illustrate several preferred embodiments of a system 100 for digitally processing an audio signal, and FIGS. 2A, 2B, 2C, and 2D provide examples of several subcomponents and combinations of subcomponents of the modules of FIGS. 1A, 1B, 1C, and 1D. Accordingly, and in at least one preferred embodiment, the systems 100 and 300 generally comprise an input device 101, a high pass filter 111, a first filter module 301, a first compressor 114, a second filter module 302, a first processing module 303, a band splitter 119, a low band compressor 130, a high band compressor 131, a second processing module 304, and an output device 102. In at least another preferred embodiment, the systems 100 and 300 generally comprise an input device 101, a high pass filter 111, a splitter 140, a first filter module 301, a first compressor 114, a first processing module 303, a band splitter 119, a low band compressor 130, a high band compressor 131, a second processing module 304, and an output device 102. In at least another embodiment, the systems 100 and 300 may also comprise a first gain element 103.


The input device 101 is at least partially structured or configured to transmit an input audio signal 201 into the system 100 of the present invention, and in at least one embodiment into the high pass filter 111. In at least another embodiment, the input device 101 is at least partially structured or configured to transmit an input audio signal 201 into the system 100 of the present invention, into the first gain element 103. The input audio signal 201 may comprise the full audible range, or portions of the audible range. The input audio signal 201 may comprise a stereo audio signal. The input device 101 may comprise at least portions of an audio device capable of audio playback. The input device 101 for instance, may comprise a stereo system, a portable music player, a mobile device, a computer, a sound or audio card, or any other device or combination of electronic circuits suitable for audio playback.


The high pass filter 111 is configured to pass through high frequencies of an audio signal, such as the input signal 201, while attenuating lower frequencies, based on a predetermined frequency. In other words, the frequencies above the predetermined frequency may be transmitted to the first filter module 301 in accordance with the present invention. In at least one embodiment, ultra-low frequency content is removed from the input audio signal, where the predetermined frequency may be selected from a range between 300 Hz and 3 kHz. The predetermined frequency however, may vary depending on the source signal, and vary in other embodiments to comprise any frequency selected from the full audible range of frequencies between 20 Hz to 20 kHz. The predetermined frequency may be tunable by a user, or alternatively be statically set. The high pass filter 111 may further comprise any circuits or combinations thereof structured to pass through high frequencies above a predetermined frequency, and attenuate or filter out the lower frequencies.


The first filter module 301 is configured to selectively boost or attenuate the gain of select frequency ranges within an audio signal, such as the high pass signal 211. For example, and in at least one embodiment, frequencies below a first frequency may be adjusted by ±X dB, while frequencies above a first frequency may be adjusted by ±Y dB. In other embodiments, a plurality of frequencies may be used to selectively adjust the gain of various frequency ranges within an audio signal. In at least one embodiment, the first filter module 301 may be implemented with a first low shelf filter 112 and a first high shelf filter 113, as illustrated in FIGS. 2A and 2B. In at least one other embodiment, the first filter module 301 may be implemented only with a first low shelf filter 112 as illustrated in FIG. 2D. In at least one other embodiment, the first filter module 301 may be implemented only with a first high shelf filter 113 as illustrated in FIG. 2C. The first low shelf filter 112 and first high shelf filter 113 may both be second-order filters. In at least one embodiment, the first low shelf filter 112 attenuates content below a first frequency, and the first high shelf filter 113 boosts content above a first frequency. In other embodiments, the frequency used for the first low shelf filter 112 and first high shelf filter 113 may comprise two different frequencies. The frequencies may be static or adjustable. Similarly, the gain adjustment (boost or attenuation) may be static or adjustable.


In at least one embodiment, the splitter 140 is configured to split a signal, such as the high pass signal 211 from the high pass filter 111. In at least one embodiment, the high pass signal 211 from the high pass filter 111 is split into a first high pass signal 210 and a second high pass signal 208.


The first compressor 114 is configured to modulate a signal, such as the first filtered signal 401 or the first high pass signal 210. The first compressor 114 may comprise an automatic gain controller. The first compressor 114 may comprise standard dynamic range compression controls such as threshold, ratio, attack and release. Threshold allows the first compressor 114 to reduce the level of the filtered signal 211 if its amplitude exceeds a certain threshold. Ratio allows the first compressor 114 to reduce the gain as determined by a ratio. Attack and release determines how quickly the first compressor 114 acts. The attack phase is the period when the first compressor 114 is decreasing gain to reach the level that is determined by the threshold. The release phase is the period that the first compressor 114 is increasing gain to the level determined by the ratio. The first compressor 114 may also feature soft and hard knees to control the bend in the response curve of the output or modulated signal 212, and other dynamic range compression controls appropriate for the dynamic compression of an audio signal. The first compressor 114 may further comprise any device or combination of circuits that is structured and configured for dynamic range compression.


In at least one embodiment, the second filter module 302 is configured to selectively boost or attenuate the gain of select frequency ranges within an audio signal, such as the modulated signal 214. In at least one embodiment, the second filter module 302 is of the same configuration as the first filter module 301. Specifically, the second filter module 302 may comprise a second low shelf filter 115 and a second high shelf filter 116. In at least one embodiment, the second filter module 302 may comprise only a high shelf filer 116. The second filter module 302 may be configured in at least a partially inverse configuration to the first filter module 301. For instance, the second filter module may use the same frequency, for instance the first frequency, as the first filter module. Further, the second filter module may adjust the gain inversely to the gain or attenuation of the first filter module, of content above the first frequency. Similarly second filter module may also adjust the gain inversely to the gain or attenuation of the of the first filter module, of content below the first frequency. In other words, the purpose of the second filter module in one embodiment may be to “undo” the gain adjustment that was applied by the first filter module.


The first processing module 303 is configured to process a signal, such as the second filtered signal 402, or the first modulated signal 214. In at least one embodiment, the first processing module 303 may comprise a peak/dip module, such as 118 represented in FIGS. 2A, 2B, 2C, and 2D. In other embodiments, the first processing module 303 may comprise a second gain element 117. In various embodiments, the processing module 303 may comprise both a second gain element 117 and a peak/dip module 118 for the processing of a signal. The second gain element 117, in at least one embodiment, may be configured to adjust the level of a signal by a static amount. The second gain element 17 may comprise an amplifier or a multiplier circuit. In other embodiments, dynamic gain elements may be used. The peak/dip module 118 is configured to shape the desired output spectrum, such as to increase or decrease overshoots or undershoots in the signal. In some embodiments, the peak/dip module may further be configured to adjust the slope of a signal, for instance for a gradual slope that gives a smoother response, or alternatively provide for a steeper slope for more sudden sounds. In at least one embodiment, the peak/dip module 118 comprises a bank of ten cascaded peak/dipping filters. The bank of ten cascaded peaking/dipping filters may further be second-order filters. In at least one embodiment, the peak/dip module 118 may comprise an equalizer, such as parametric or graphic equalizers.


The band splitter 119 is configured to split a signal, such as the processed signal 403. In at least one embodiment, the signal is split into at least low band signal 220 and a high band signal 222, and preferably also a mid band signal 221. Each band may be the output of a fourth order section, which may be further realized as the cascade of second order biquad filters. In other embodiments, the band splitter may comprise any combination of circuits appropriate for splitting a signal into three frequency bands. At least the low, and high bands, and preferably a mid band may be predetermined ranges, or may be dynamically determined based on the frequency itself, i.e. a signal may be split into three even frequency bands, or by percentage. The different bands may further be defined or configured by a user and/or control mechanism.


A low band compressor 130 is configured to modulate the low band signal 220, and a high band compressor 131 is configured to modulate the high band signal 222. In at least one embodiment, each of the low band compressor 130 and high band compressor 131 may be the same as the first compressor 114. Accordingly, each of the low band compressor 130 and high band compressor 131 may each be configured to modulate a signal. Each of the compressors 130, 131 may comprise an automatic gain controller, or any combination of circuits appropriate for the dynamic range compression of an audio signal.


A second processing module 304 is configured to process at least one signal, such as the modulated low band signal 230 and the modulated high band signal 231, and preferably also a mid-band signal 221. Accordingly, the second processing module 304 may comprise a summing module 132 configured to combine a plurality of signals. The summing module 132 may comprise a mixer structured to combine two or more signals into a composite signal. The summing module 132 may comprise any circuits or combination thereof structured or configured to combine two or more signals. In at least one embodiment, the summing module 132 comprises individual gain controls for each of the incoming signals, such as the modulated low band signal 230 and the modulated high band signal 231, and preferably also a mid-band signal 221. In at least one embodiment, the second processing module 304 may further comprise a third gain element 133. The third gain element 133, in at least one embodiment, may be the same as the second gain element 117. The third gain element 133 may thus comprise an amplifier or multiplier circuit to adjust the signal, such as the combined signal, by a predetermined amount. The output device 102 may be structured to further process the output signal 404. The output device 102 may also be structured and/or configured for playback of the output signal 404.


As diagrammatically represented, FIGS. 3A, 3B, 3C, 3D, 4A, 4B, 4C, and 4D illustrate other embodiments directed to a method for digitally processing an audio signal, which may in at least one embodiment incorporate the components or combinations thereof from the systems 100 and/or 300 referenced above. Each step of the method in FIGS. 3A, 3B, 3C, 3D, 4A, 4B, 4C, and 4D as detailed below may also be in the form of a code segment directed to at least one embodiment of the present invention, which is stored on a non-transitory computer readable medium, for execution by a computer to process an input audio signal.


Accordingly, an input audio signal is filtered, as in 501, with a high pass filter to create a high pass signal. Alternatively, the input audio signal is first processed, as in 510, with a first gain element to create a first gain signal. The high pass filter is configured to pass through high frequencies of a signal, such as the input signal, or the first gain signal, while attenuating lower frequencies. In at least one embodiment, ultra-low frequency content is removed by the high-pass filter. In at least one embodiment, the high pass filter may comprise a fourth-order filter realized as the cascade of two second-order biquad sections. The reason for using a fourth order filter broken into two second order sections is that it allows the filter to retain numerical precision in the presence of finite word length effects, which can happen in both fixed and floating point implementations.


An example implementation of such an embodiment may assume a form similar to the following:

    • Two memory locations are allocated, designated as d(k−1) and d(k−2), with each holding a quantity known as a state variable. For each input sample x(k), a quantity d(k) is calculated using the coefficients a1 and a2:

      d(k)=x(k)−a1*d(k−1)−a2*d(k−2)
    • The output y(k) is then computed, based on coefficients b0, b1, and b2, according to:

      y(k)=b0*d(k)+b1*d(k−1)+b2*d(k−2)


The above computation comprising five multiplies and four adds is appropriate for a single channel of second-order biquad section. Accordingly, because the fourth-order high pass filter is realized as a cascade of two second-order biquad sections, a single channel of fourth order input high pass filter would require ten multiples, four memory locations, and eight adds.


The high pass signal from the high pass filter is then filtered, as in 502, with a first filter module to create a first filtered signal. The first filter module is configured to selectively boost or attenuate the gain of select frequency ranges within an audio signal, such as the high pass signal. Accordingly, the first filter module may comprise a second order low shelf filter and a second order high shelf filter in at least one embodiment. In at least one embodiment, the first filter module boosts the content above a first frequency by a certain amount, and attenuates the content below a first frequency by a certain amount, before presenting the signal to a compressor or dynamic range controller. This allows the dynamic range controller to trigger and adjust higher frequency material, whereas it is relatively insensitive to lower frequency material.


In at least one embodiment, the high pass signal 211 from the high pass filter 111 is split, as in 511, with a splitter 140, into a first high pass signal 210, and a second high pass signal 208. In at least one embodiment, the second high pass signal is filtered with a first filter module. In at least one embodiment the first filtered signal 401 from the first filter module 301 is then modulated, as in 503, with a first compressor 114. In at least one embodiment, the first high pass signal 210 is modulated with a first compressor 114 as in 513. The first compressor may comprise an automatic or dynamic gain controller, or any circuits appropriate for the dynamic compression of an audio signal. Accordingly, the compressor may comprise standard dynamic range compression controls such as threshold, ratio, attack and release. An example implementation of the first compressor may assume a form similar to the following:


The compressor first computes an approximation of the signal level, where att represents attack time; rel represents release time; and invThr represents a precomputed threshold:

















temp = abs(x(k))



if temp > level (k−1)



  level(k) = att * (level(k−1) − temp) + temp



else



  level = rel * (level(k−1) − temp) + temp










This level computation is done for each input sample. The ratio of the signal's level to invThr then determines the next step. If the ratio is less than one, the signal is passed through unaltered. If the ratio exceeds one, a table in the memory may provide a constant that is a function of both invThr and level:

















if (level * thr < 1)



  output(k) = x(k)



else



  index = floor(level * invThr)



if (index > 99)



  index = 99



gainReduction = table[index]



output(k) = gainReduction * x(k)










In at least one embodiment, the modulated signal from the first compressor is then filtered, as in 504, with a second filter module to create a second filtered signal. The second filter module is configured to selectively boost or attenuate the gain of select frequency ranges within an audio signal, such as the modulated signal. Accordingly, the second filter module may comprise a second order low shelf filter and a second order high shelf filter in at least one embodiment. In at least one embodiment, the second filter module boosts the content above a second frequency by a certain amount, and attenuates the content below a second frequency by a certain amount. In at least one embodiment, the second filter module adjusts the content below the first specified frequency by a fixed amount, inverse to the amount that was removed by the first filter module. By way of example, if the first filter module boosted content above a first frequency by +X dB and attenuated content below a first frequency by −Y dB, the second filter module may then attenuate the content above the first frequency by −X dB, and boost the content below the first frequency by +Y dB. In other words, the purpose of the second filter module in one embodiment may be to “undo” the filtering that was applied by the first filter module.


In at least one embodiment, the second filtered signal from the second filter module is then processed, as in 505, with a first processing module to create a processed signal. In at least one embodiment, the modulated signal from the first compressor is then processed, as in 505′, with a first processing module to create a processed signal. The processing module may comprise a second gain element configured to adjust the level of the signal. This adjustment, for instance, may be necessary because the peak-to-average ratio was modified by the first compressor. The processing module may comprise a peak/dip module. The peak/dip module may comprise ten cascaded second-order filters in at least one embodiment. The peak/dip module may be used to shape the desired output spectrum of the signal. In at least one embodiment, the first processing module comprises only the peak/dip module. In other embodiments, the first processing module comprises a gain element followed by a peak/dip module.


The processed signal from the first processing module is then split, as in 506, with a band splitter into at least a low band signal and a high band signal, and preferably also a mid band signal. The band splitter may comprise any circuit or combination of circuits appropriate for splitting a signal into a plurality of signals of different frequency ranges. In at least one embodiment, the band splitter comprises a fourth-order band-splitting bank. In this embodiment, each of the low band and high band, and preferably also a mid band, are yielded as the output of a fourth-order section, realized as the cascade of second-order biquad filters.


The low band signal is modulated, as in 507, with a low band compressor to create a modulated low band signal. The low band compressor may be configured and/or computationally identical to the first compressor in at least one embodiment. The high band signal is modulated, as in 508, with a high band compressor to create a modulated high band signal. The high band compressor may be configured and/or computationally identical to the first compressor in at least one embodiment.


At least the modulated low band signal and modulated high band signal, and preferably also a mid band signal, are then processed, as in 509, with a second processing module. The second processing module comprises at least a summing module. The summing module is configured to combine a plurality of signals into one composite signal. In at least one embodiment, the summing module may further comprise individual gain controls for each of the incoming signals, such as the modulated low band signal and the modulated high band signal, and preferably also a mid band signal. By way of example, an output of the summing module may be calculated by:

out=w0*low+w1*mid+w2*high


The coefficients w0, w1, and w2 represent different gain adjustments. The second processing module may further comprise a second gain element. The second gain element may be the same as the first gain element in at least one embodiment. The second gain element may provide a final gain adjustment. Finally, the second processed signal is transmitted as the output signal.


As diagrammatically represented, FIG. 4 illustrates another embodiment directed to a method for digitally processing an audio signal, which may in at least one embodiment incorporate the components or combinations thereof from the systems 100 and/or 300 referenced above. Because the individual components of FIG. 4 have been discussed in detail above, they will not be discussed here. Further, each step of the method in FIG. 4 as detailed below may also be in the form of a code segment directed to at least one embodiment of the present invention, which is stored on a non-transitory computer readable medium, for execution by a computer to process an input audio signal.


Accordingly, an input audio signal such as the first gain signal is first filtered, as in 501, with a high pass filter. The high pass signal from the high pass filter is then filtered, as in 601, with a first low shelf filter. The signal from the first low shelf filter is then filtered with a first high shelf filter, as in 602. The first filtered signal from the first low shelf filter is then modulated with a first compressor, as in 503. In at least one embodiment, the modulated signal from the first compressor is filtered with a second low shelf filter as in 611. The signal from the low shelf filter is then filtered with a second high shelf filter, as in 612. In at least one embodiment, the modulated signal from the first compressor is filtered with a second high shelf filter as in 612′. In at least one embodiment, the second filtered signal from the second low shelf filter, is then gain-adjusted with a second gain element, as in 621. In at least one embodiment, the second filtered signal from the second high shelf filter, is then gain-adjusted with a second gain element, as in 621. The signal from the second gain element is further processed with a peak/dip module, as in 622. The processed signal from the peak/dip module is then split into at least a low band signal and a high band signal, but preferably also a mid band signal, as in 506.


The low band signal is modulated with a low band compressor, as in 507. The high band signal is modulated with a high band compressor, as in 508. At least the modulated low band signal and modulated high band signal, and also preferably a mid band signal, are then combined with a summing module, as in 631. The combined signal is then gain adjusted with a third gain element in order to create the output signal, as in 632.


Any of the above methods may be completed in sequential order in at least one embodiment, though they may be completed in any other order. In at least one embodiment, the above methods may be exclusively performed, but in other embodiments, one or more steps of the methods as described may be skipped


Since many modifications, variations and changes in detail can be made to the described preferred embodiment of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents. Furthermore, in that various embodiments may include one, two or three of a specific element, such as a gain controller, reference to them as first, second and third is included for facilitated reference when more than one is included, but should not be viewed as limiting to require one, two or three in any or all instances. For example, reference to a second gain element does not require that all embodiments include a first gain element.


Now that the invention has been described,

Claims
  • 1. A system for digital signal processing of an audio signal comprising: a high pass filter configured to filter an audio signal to create a high pass signal,a first filter module configured to filter the high pass signal to create a first filtered signal,a first compressor configured to modulate the first filtered signal to create a modulated signal,a second filter module configured to filter the modulated signal to create a second filtered signal,a first processing module configured to process the second filtered signal to create a processed signal,a band splitter configured to split the processed signal into at least a first low band signal and a second high band signal,at least a first modulator structured to modulate said first band signal and a second modulator structured to modulate said second band signal to create a first and a second modulated band signal, anda summing module configured to combine at least the first and second modulated band signals to create a combined signal.
  • 2. A system as recited in claim 1 wherein the first filter module comprises: a first low shelf filter configured to filter the high pass signal to create a first low shelf signal,a first high shelf filter configured to filter the first low shelf signal to create the first filtered signal.
  • 3. A system as recited in claim 1 wherein said second filter module comprises: a second low shelf filter configured to filter the modulated signal to create a second low shelf signal, anda second high shelf filter configured to filter second low shelf signal to create the second filtered signal.
  • 4. A system as recited in claim 1 wherein said first filter module comprises a low shelf filter and said second filter module comprises a high shelf filter.
  • 5. A system as recited in claim 1 further comprising a first gain element configured to adjust a gain of the input audio signal prior to said high pass filter.
  • 6. A system as recited in claim 1 wherein said first processing module comprises a gain element configured to adjust the gain of the second filtered signal to create a gain signal; and a peak/dip module configured to process the gain signal to create the processed signal.
  • 7. A system as recited in claim 1 wherein said summing module further comprises a gain element configured to adjust the gain of the combined signal to create the output signal.
  • 8. A system as recited in claim 1 wherein said band splitter splits the processed signal into at least a low band signal and a high band signal, and said first modulator comprises a band compressor.
  • 9. A system as recited in claim 8 wherein said first modulator comprises a low band modulator and said second modulator comprises a high band modulator.
CLAIM OF PRIORITY

The present application is a continuation application of previously filed, now pending application having Ser. No. 15/906,614, filed on Feb. 27, 2018, which is a continuation application of U.S. Ser. No. 15/214,146, filed on Jul. 19, 2016, which matured into U.S. Pat. No. 9,906,858 on Feb. 27, 2018, which is a continuation-in-part application of previously filed Ser. No. 14/059,669, filed on Oct. 22, 2013, which matured into U.S. Pat. No. 9,397,629 on Jul. 19, 2016, which are incorporated herein by reference.

US Referenced Citations (314)
Number Name Date Kind
2643729 McCracken Jun 1953 A
3430007 Thielen Feb 1969 A
3795876 Takashi et al. Mar 1974 A
3813687 Geil May 1974 A
4162462 Endoh et al. Jul 1979 A
4184047 Langford Jan 1980 A
4218950 Uetrecht Aug 1980 A
4226533 Snowman Oct 1980 A
4257325 Bertagni Mar 1981 A
4353035 Schröder Oct 1982 A
4356558 Owen et al. Oct 1982 A
4363007 Haramoto et al. Dec 1982 A
4392027 Bock Jul 1983 A
4399474 Coleman, Jr. Aug 1983 A
4412100 Orban Oct 1983 A
4458362 Berkovitz et al. Jul 1984 A
4489280 Bennett, Jr. et al. Dec 1984 A
4517415 Laurence May 1985 A
4538297 Waller Aug 1985 A
4549289 Schwartz et al. Oct 1985 A
4584700 Scholz Apr 1986 A
4602381 Cugnini et al. Jul 1986 A
4612665 Inami et al. Sep 1986 A
4641361 Rosback Feb 1987 A
4677645 Kaniwa et al. Jun 1987 A
4696044 Waller, Jr. Sep 1987 A
4701953 White Oct 1987 A
4704726 Gibson Nov 1987 A
4715559 Fuller Dec 1987 A
4739514 Short et al. Apr 1988 A
4815142 Imreh Mar 1989 A
4856068 Quatieri, Jr. et al. Aug 1989 A
4887299 Cummins et al. Dec 1989 A
4997058 Bertagni Mar 1991 A
5007707 Bertagni Apr 1991 A
5073936 Gurike et al. Dec 1991 A
5133015 Scholz Jul 1992 A
5195141 Jang Mar 1993 A
5210704 Husseiny May 1993 A
5210806 Kihara et al. May 1993 A
5226076 Baumhauer, Jr. et al. Jul 1993 A
5355417 Burdisso et al. Oct 1994 A
5361381 Short Nov 1994 A
5384856 Kyouno et al. Jan 1995 A
5420929 Geddes et al. May 1995 A
5425107 Bertagni et al. Jun 1995 A
5463695 Werrbach Oct 1995 A
5465421 McCormick et al. Nov 1995 A
5467775 Callahan et al. Nov 1995 A
5473214 Hildebrand Dec 1995 A
5511129 Craven et al. Apr 1996 A
5515444 Burdisso et al. May 1996 A
5539835 Bertagni et al. Jul 1996 A
5541866 Sato et al. Jul 1996 A
5572443 Emoto et al. Nov 1996 A
5615275 Bertagni Mar 1997 A
5617480 Ballard et al. Apr 1997 A
5638456 Conley et al. Jun 1997 A
5640685 Komoda Jun 1997 A
5671287 Gerzon Sep 1997 A
5693917 Bertagni et al. Dec 1997 A
5699438 Smith et al. Dec 1997 A
5727074 Hildebrand Mar 1998 A
5737432 Werrbach Apr 1998 A
5812684 Mark Sep 1998 A
5828768 Eatwell et al. Oct 1998 A
5832097 Armstrong et al. Nov 1998 A
5838805 Warnaka et al. Nov 1998 A
5848164 Levine Dec 1998 A
5861686 Lee Jan 1999 A
5862461 Yoshizawa et al. Jan 1999 A
5872852 Dougherty Feb 1999 A
5901231 Parrella et al. May 1999 A
5990955 Koz Nov 1999 A
6058196 Heron May 2000 A
6078670 Beyer Jun 2000 A
6093144 Jaeger et al. Jul 2000 A
6108431 Bachler Aug 2000 A
6195438 Yumoto et al. Feb 2001 B1
6201873 Dal Farra Mar 2001 B1
6202601 Ouellette et al. Mar 2001 B1
6208237 Saiki et al. Mar 2001 B1
6244376 Granzotto Jun 2001 B1
6263354 Gandhi Jul 2001 B1
6285767 Klayman Sep 2001 B1
6292511 Goldston et al. Sep 2001 B1
6317117 Goff Nov 2001 B1
6318797 Böhm et al. Nov 2001 B1
6332029 Azima et al. Dec 2001 B1
6343127 Billoud Jan 2002 B1
6518852 Derrick Feb 2003 B1
6529611 Kobayashi et al. Mar 2003 B2
6535846 Shashoua Mar 2003 B1
6570993 Fukuyama May 2003 B1
6587564 Cusson Jul 2003 B1
6618487 Azima et al. Sep 2003 B1
6661897 Smith Dec 2003 B2
6661900 Allred et al. Dec 2003 B1
6760451 Craven et al. Jul 2004 B1
6772114 Sluijter et al. Aug 2004 B1
6839438 Riegelsberger et al. Jan 2005 B1
6847258 Ishida et al. Jan 2005 B2
6871525 Withnall et al. Mar 2005 B2
6907391 Bellora et al. Jun 2005 B2
6999826 Zhou et al. Feb 2006 B1
7006653 Guenther Feb 2006 B2
7016746 Wiser et al. Mar 2006 B2
7024001 Nakada Apr 2006 B1
7058463 Ruha et al. Jun 2006 B1
7123728 King et al. Oct 2006 B2
7236602 Gustavsson Jun 2007 B2
7254243 Bongiovi Aug 2007 B2
7266205 Miller Sep 2007 B2
7269234 Klingenbrunn et al. Sep 2007 B2
7274795 Bongiovi Sep 2007 B2
7430300 Vosburgh et al. Sep 2008 B2
7519189 Bongiovi Apr 2009 B2
7577263 Tourwe Aug 2009 B2
7613314 Camp, Jr. Nov 2009 B2
7676048 Tsutsui Mar 2010 B2
7711129 Lindahl May 2010 B2
7711442 Ryle et al. May 2010 B2
7747447 Christensen et al. Jun 2010 B2
7764802 Oliver Jul 2010 B2
7778718 Janke et al. Aug 2010 B2
7916876 Helsloot Mar 2011 B1
8068621 Okabayashi et al. Nov 2011 B2
8144902 Johnston Mar 2012 B2
8160274 Bongiovi Apr 2012 B2
8175287 Ueno et al. May 2012 B2
8218789 Bharitkar et al. Jul 2012 B2
8229136 Bongiovi Jul 2012 B2
8284955 Bongiovi et al. Oct 2012 B2
8385864 Dickson et al. Feb 2013 B2
8462963 Bongiovi Jun 2013 B2
8472642 Bongiovi Jun 2013 B2
8503701 Miles et al. Aug 2013 B2
8565449 Bongiovi Oct 2013 B2
8577676 Muesch Nov 2013 B2
8619998 Walsh et al. Dec 2013 B2
8705765 Bongiovi Apr 2014 B2
8750538 Avendano et al. Jun 2014 B2
8811630 Burlingame Aug 2014 B2
8879743 Mitra Nov 2014 B1
9195433 Bongiovi et al. Nov 2015 B2
9264004 Bongiovi et al. Feb 2016 B2
9276542 Bongiovi et al. Mar 2016 B2
9281794 Bongiovi et al. Mar 2016 B1
9344828 Bongiovi et al. May 2016 B2
9348904 Bongiovi et al. May 2016 B2
9350309 Bongiovi et al. May 2016 B2
9397629 Bongiovi et al. Jul 2016 B2
9398394 Bongiovi et al. Jul 2016 B2
9413321 Bongiovi et al. Aug 2016 B2
9564146 Bongiovi et al. Feb 2017 B2
9615189 Copt et al. Apr 2017 B2
9621994 Bongiovi et al. Apr 2017 B1
9638672 Butera, III et al. May 2017 B2
9741355 Bongiovi et al. Aug 2017 B2
9793872 Bongiovi et al. Oct 2017 B2
9883318 Bongiovi et al. Jan 2018 B2
9906858 Bongiovi et al. Feb 2018 B2
9906867 Bongiovi et al. Feb 2018 B2
9998832 Bongiovi et al. Jun 2018 B2
1006947 Bongiovi et al. Sep 2018 A1
1015833 Bongiovi et al. Dec 2018 A1
10158337 Bongiovi et al. Dec 2018 B2
10313791 Bongiovi Jun 2019 B2
10666216 Bongiovi et al. May 2020 B2
10701505 Copt et al. Jun 2020 B2
20010008535 Lanigan Jul 2001 A1
20010043704 Schwartz Nov 2001 A1
20010046304 Rast Nov 2001 A1
20020057808 Goldstein May 2002 A1
20020071481 Goodings Jun 2002 A1
20020094096 Paritsky et al. Jul 2002 A1
20030016838 Paritsky et al. Jan 2003 A1
20030023429 Claesson et al. Jan 2003 A1
20030035555 King et al. Feb 2003 A1
20030043940 Janky et al. Mar 2003 A1
20030112088 Bizjak Jun 2003 A1
20030138117 Goff Jul 2003 A1
20030142841 Wiegand Jul 2003 A1
20030164546 Giger Sep 2003 A1
20030179891 Rabinowitz et al. Sep 2003 A1
20030216907 Thomas Nov 2003 A1
20040003805 Ono et al. Jan 2004 A1
20040005063 Klayman Jan 2004 A1
20040008851 Hagiwara Jan 2004 A1
20040022400 Magrath Feb 2004 A1
20040042625 Brown Mar 2004 A1
20040044804 MacFarlane Mar 2004 A1
20040086144 Kallen May 2004 A1
20040103588 Allaei Jun 2004 A1
20040138769 Akiho Jul 2004 A1
20040146170 Zint Jul 2004 A1
20040189264 Matsuura et al. Sep 2004 A1
20040208646 Choudhary et al. Oct 2004 A1
20050013453 Cheung Jan 2005 A1
20050090295 Ali et al. Apr 2005 A1
20050117771 Vosburgh et al. Jun 2005 A1
20050129248 Kraemer et al. Jun 2005 A1
20050175185 Korner Aug 2005 A1
20050201572 Lindahl et al. Sep 2005 A1
20050249272 Kirkeby et al. Nov 2005 A1
20050254564 Tsutsui Nov 2005 A1
20060034467 Sleboda et al. Feb 2006 A1
20060045294 Smyth Mar 2006 A1
20060064301 Aguilar et al. Mar 2006 A1
20060098827 Paddock et al. May 2006 A1
20060115107 Vincent et al. Jun 2006 A1
20060126851 Yuen et al. Jun 2006 A1
20060126865 Blamey et al. Jun 2006 A1
20060138285 Oleski et al. Jun 2006 A1
20060140319 Eldredge et al. Jun 2006 A1
20060153281 Karlsson Jul 2006 A1
20060189841 Pluvinage Aug 2006 A1
20060291670 King et al. Dec 2006 A1
20070010132 Nelson Jan 2007 A1
20070030994 Ando et al. Feb 2007 A1
20070056376 King Mar 2007 A1
20070119421 Lewis et al. May 2007 A1
20070150267 Honma et al. Jun 2007 A1
20070173990 Smith et al. Jul 2007 A1
20070177459 Behn Aug 2007 A1
20070206643 Egan Sep 2007 A1
20070223713 Gunness Sep 2007 A1
20070223717 Boersma Sep 2007 A1
20070253577 Yen et al. Nov 2007 A1
20080031462 Walsh et al. Feb 2008 A1
20080040116 Cronin Feb 2008 A1
20080049948 Christoph Feb 2008 A1
20080069385 Revit Mar 2008 A1
20080123870 Stark May 2008 A1
20080123873 Bjorn-Josefsen et al. May 2008 A1
20080165989 Seil et al. Jul 2008 A1
20080181424 Schulein et al. Jul 2008 A1
20080212798 Zartarian Sep 2008 A1
20080255855 Lee et al. Oct 2008 A1
20090022328 Neugebauer et al. Jan 2009 A1
20090054109 Hunt Feb 2009 A1
20090080675 Smirnov et al. Mar 2009 A1
20090086996 Bongiovi et al. Apr 2009 A1
20090116652 Kirkeby et al. May 2009 A1
20090282810 Leone et al. Nov 2009 A1
20090290725 Huang Nov 2009 A1
20090296959 Bongiovi Dec 2009 A1
20100045374 Wu et al. Feb 2010 A1
20100246832 Villemoes et al. Sep 2010 A1
20100256843 Bergstein et al. Oct 2010 A1
20100278364 Berg Nov 2010 A1
20100303278 Sahyoun Dec 2010 A1
20110002467 Nielsen Jan 2011 A1
20110007907 Park et al. Jan 2011 A1
20110013736 Tsukamoto et al. Jan 2011 A1
20110065408 Kenington et al. Mar 2011 A1
20110087346 Larsen et al. Apr 2011 A1
20110096936 Gass Apr 2011 A1
20110194712 Potard Aug 2011 A1
20110230137 Hicks et al. Sep 2011 A1
20110257833 Trush et al. Oct 2011 A1
20110280411 Cheah et al. Nov 2011 A1
20120008798 Ong Jan 2012 A1
20120014553 Bonanno Jan 2012 A1
20120020502 Adams Jan 2012 A1
20120022842 Amadu Jan 2012 A1
20120063611 Kimura Mar 2012 A1
20120099741 Gotoh et al. Apr 2012 A1
20120170759 Yuen et al. Jul 2012 A1
20120170795 Sancisi et al. Jul 2012 A1
20120189131 Ueno et al. Jul 2012 A1
20120213034 Imran Aug 2012 A1
20120213375 Mahabub et al. Aug 2012 A1
20120300949 Rauhala Nov 2012 A1
20120302920 Bridger et al. Nov 2012 A1
20130083958 Katz et al. Apr 2013 A1
20130129106 Sapiejewski May 2013 A1
20130162908 Son et al. Jun 2013 A1
20130163767 Gauger, Jr. et al. Jun 2013 A1
20130163783 Burlingame Jun 2013 A1
20130169779 Pedersen Jul 2013 A1
20130220274 Deshpande et al. Aug 2013 A1
20130227631 Sharma et al. Aug 2013 A1
20130242191 Leyendecker Sep 2013 A1
20130251175 Bongiovi et al. Sep 2013 A1
20130288596 Suzuki et al. Oct 2013 A1
20130338504 Demos et al. Dec 2013 A1
20130343564 Darlington Dec 2013 A1
20140067236 Henry et al. Mar 2014 A1
20140119583 Valentine et al. May 2014 A1
20140126734 Gauger, Jr. et al. May 2014 A1
20140261301 Leone Sep 2014 A1
20140379355 Hosokawsa Dec 2014 A1
20150039250 Rank Feb 2015 A1
20150194158 Oh et al. Jul 2015 A1
20150208163 Hallberg et al. Jul 2015 A1
20150215720 Carroll Jul 2015 A1
20160209831 Pal Jul 2016 A1
20170072305 Watanabe Mar 2017 A1
20170188989 Copt et al. Jul 2017 A1
20170193980 Bongiovi et al. Jul 2017 A1
20170272887 Copt et al. Sep 2017 A1
20170345408 Hong et al. Nov 2017 A1
20180077482 Yuan Mar 2018 A1
20180091109 Bongiovi et al. Mar 2018 A1
20180102133 Bongiovi et al. Apr 2018 A1
20180139565 Norris et al. May 2018 A1
20180226064 Seagriff et al. Aug 2018 A1
20190020950 Bongiovi et al. Jan 2019 A1
20190069114 Tai et al. Feb 2019 A1
20190075388 Schrader et al. Mar 2019 A1
20190318719 Copt et al. Oct 2019 A1
20190387340 Audfray et al. Dec 2019 A1
20200053503 Butera, III et al. Feb 2020 A1
Foreign Referenced Citations (146)
Number Date Country
9611417 Feb 1999 BR
96113723 Jul 1999 BR
2533221 Jun 1995 CA
2161412 Apr 2000 CA
2854086 Dec 2018 CA
1139842 Jan 1997 CN
1173268 Feb 1998 CN
1221528 Jun 1999 CN
1357136 Jul 2002 CN
1391780 Jan 2003 CN
1879449 Dec 2006 CN
1910816 Feb 2007 CN
101163354 Apr 2008 CN
101277331 Oct 2008 CN
101518083 Aug 2009 CN
101536541 Sep 2009 CN
101720557 Jun 2010 CN
101946526 Jan 2011 CN
101964189 Feb 2011 CN
102265641 Nov 2011 CN
102652337 Aug 2012 CN
102754151 Oct 2012 CN
102822891 Dec 2012 CN
102855882 Jan 2013 CN
103004237 Mar 2013 CN
203057339 Jul 2013 CN
103247297 Aug 2013 CN
103250209 Aug 2013 CN
103262577 Aug 2013 CN
103348697 Oct 2013 CN
103455824 Dec 2013 CN
19826171 Oct 1999 DE
10116166 Oct 2002 DE
0206746 Aug 1992 EP
0541646 Jan 1995 EP
0580579 Jun 1998 EP
0698298 Feb 2000 EP
0932523 Jun 2000 EP
0666012 Nov 2002 EP
2509069 Oct 2012 EP
2814267 Oct 2016 EP
2218599 Oct 1998 ES
2249788 Oct 1998 ES
2219949 Aug 1999 ES
2003707 Mar 1979 GB
2089986 Jun 1982 GB
2320393 Dec 1996 GB
245250 Sep 2020 IL
3150910 Jun 1991 JP
7106876 Apr 1995 JP
2005500768 Jan 2005 JP
2011059714 Mar 2011 JP
1020040022442 Mar 2004 KR
1319288 Jun 1987 SU
401713 Aug 2000 TW
WO 9219080 Oct 1992 WO
WO 1993011637 Jun 1993 WO
WO 9321743 Oct 1993 WO
WO 9427331 Nov 1994 WO
WO 9514296 May 1995 WO
WO 9531805 Nov 1995 WO
WO 9535628 Dec 1995 WO
WO 9601547 Jan 1996 WO
WO 9611465 Apr 1996 WO
WO 9708847 Mar 1997 WO
WO 9709698 Mar 1997 WO
WO 9709840 Mar 1997 WO
WO 9709841 Mar 1997 WO
WO 9709842 Mar 1997 WO
WO 9709843 Mar 1997 WO
WO 9709844 Mar 1997 WO
WO 9709845 Mar 1997 WO
WO 9709846 Mar 1997 WO
WO 9709848 Mar 1997 WO
WO 9709849 Mar 1997 WO
WO 9709852 Mar 1997 WO
WO 9709853 Mar 1997 WO
WO 9709854 Mar 1997 WO
WO 9709855 Mar 1997 WO
WO 9709856 Mar 1997 WO
WO 9709857 Mar 1997 WO
WO 9709858 Mar 1997 WO
WO 9709859 Mar 1997 WO
WO 9709861 Mar 1997 WO
WO 9709862 Mar 1997 WO
WO 9717818 May 1997 WO
WO 9717820 May 1997 WO
WO 9813942 Apr 1998 WO
WO 9816409 Apr 1998 WO
WO 9828942 Jul 1998 WO
WO 9831188 Jul 1998 WO
WO 9834320 Aug 1998 WO
WO 9839947 Sep 1998 WO
WO 9842536 Oct 1998 WO
WO 9843464 Oct 1998 WO
WO 9852381 Nov 1998 WO
WO 9852383 Nov 1998 WO
WO 9853638 Nov 1998 WO
WO 9902012 Jan 1999 WO
WO 9908479 Feb 1999 WO
WO 9911490 Mar 1999 WO
WO 9912387 Mar 1999 WO
WO 9913684 Mar 1999 WO
WO 9921397 Apr 1999 WO
WO 9935636 Jul 1999 WO
WO 9935883 Jul 1999 WO
WO 9937121 Jul 1999 WO
WO 9938155 Jul 1999 WO
WO 9941939 Aug 1999 WO
WO 9952322 Oct 1999 WO
WO 9952324 Oct 1999 WO
WO 9956497 Nov 1999 WO
WO 9962294 Dec 1999 WO
WO 9965274 Dec 1999 WO
WO 0001264 Jan 2000 WO
WO 0002417 Jan 2000 WO
WO 0007408 Feb 2000 WO
WO 0007409 Feb 2000 WO
WO 0013464 Mar 2000 WO
WO 0015003 Mar 2000 WO
WO 0033612 Jun 2000 WO
WO 0033613 Jun 2000 WO
WO 03104924 Dec 2003 WO
WO 2006020427 Feb 2006 WO
WO 2007092420 Aug 2007 WO
WO 2008067454 Jun 2008 WO
WO 2009070797 Jun 2009 WO
WO 2009102750 Aug 2009 WO
WO 2009114746 Sep 2009 WO
WO 2009155057 Dec 2009 WO
WO 2010027705 Mar 2010 WO
WO 2010051354 May 2010 WO
WO 2011081965 Jul 2011 WO
WO 2012134399 Oct 2012 WO
WO 2013055394 Apr 2013 WO
WO 2013076223 May 2013 WO
WO 2014201103 Dec 2014 WO
WO 2015061393 Apr 2015 WO
WO 2015077681 May 2015 WO
WO 2016019263 Feb 2016 WO
WO 2016022422 Feb 2016 WO
WO 2016144861 Sep 2016 WO
WO 2019051075 Mar 2019 WO
WO2019200119 Oct 2019 WO
WO 2020028833 Feb 2020 WO
WO2020132060 Jun 2020 WO
Non-Patent Literature Citations (2)
Entry
NovaSound Int., http://www.novasoundint.com/new_page_t.htm, 2004.
Stephan Peus et al. “Natürliche Hören mite künstlichem Kopf”, Funkschau—Zeitschrift für elektronische Kommunikation, Dec. 31, 1983, pp. 1-4, XP055451269. Web: https://www.neumann.com/?lang-en&id=hist_microphones&cid=ku80_publications.
Related Publications (1)
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20200007983 A1 Jan 2020 US
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Child 16431386 US
Parent 15214146 Jul 2016 US
Child 15906614 US
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Parent 14059669 Oct 2013 US
Child 15214146 US