Doppler compensation for coaxial and offset loudspeakers

Abstract

Audio processor (700) comprising: an audio splitter for separating a first frequency band from a second frequency band, the first frequency band having a lower frequency band than the second frequency band; a displacement estimation unit (608) for estimating a predicted displacement of a woofer sound driver (616) from information about the first frequency band; an interpolation device for interpolating an adjustment at the second frequency band to compensate for the estimated displacement; and a circuit arrangement for supplying the adapted second frequency band to a receiver.

Description

Area of ​​Revelation

[0001] This application relates to the field of audio signal processing and more specifically to providing Doppler compensation for coaxial and offset loudspeakers. background

[0002] Consumers of audio products expect high-quality audio and linear response from audio processing applications.

[0003] DE 10 2015 121 528 A1 relates to a method for controlling the diaphragm excursion of an electrodynamic loudspeaker. The audio input signal is divided into bass and treble band signals. The instantaneous diaphragm excursion is determined based on the bass band signal and compared with a excursion limit criterion. The bass band signal is limited to generate a excursion-limited audio signal, which is combined with the treble band signal. This protects the loudspeaker from mechanical damage while maintaining sound quality.

[0004] US 2016 / 0 105 742 A1 relates to a signal processor comprising a signal input having an input bandwidth, a first converter output; a second converter output; a filter network connected to the signal input, the first converter output, and the second converter output, the filter network being configured to output a first portion of the input bandwidth at the first converter output and a second portion of the input bandwidth at the second converter output; and a control module coupled to the filter network and configured to adjust the first and second portions of the input bandwidth in response to signal degradations at the first converter output.

[0005] JP H02-90 894 A relates to the prevention of cross-modulation distortion of a loudspeaker by frequency-modulating a high-frequency component using a phase-inverted low-frequency signal. The resulting signal, consisting of the low-frequency component and the frequency-modulated output, is radiated from the loudspeaker. The system includes circuits for splitting the input signal into high-frequency and low-frequency components, a circuit for phase-inverting the low-frequency component, a circuit for FM-modulating the high-frequency component using the phase-inverted low-frequency signal, and a circuit for mixing the components for output from the loudspeaker. This cancels the Doppler effect and prevents cross-modulation distortion. Brief description of the drawings

[0006] The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with common industry practice, various features are not drawn to scale and are used for illustrative purposes only. Indeed, the dimensions of the various features may be arbitrarily increased or decreased for clarity of discussion. Fig. Figure 1A is a perspective external view of a loudspeaker that may be configured with coaxial or concentric sound drivers. Fig. Figure 1B is another perspective external view of a loudspeaker. Fig. Figure 2A is a perspective view of a coaxial loudspeaker system, particularly a woofer with a concentric compression tweeter. Fig. Figure 2B is a block diagram of a system with concentric loudspeakers, in particular a woofer with a concentric conventional tweeter. Fig. Figure 2C is a block diagram illustrating a standalone woofer that can be used in configurations where the woofer and tweeter are offset from each other. Fig. Figure 3 shows a schematic representation of an electrical model of a loudspeaker system. Fig. Figure 4 is a block diagram of a possible implementation of a linearization subsystem. Fig. Figure 5 is an illustration of a modulation of an acoustic waveform. Fig. 6 is a block diagram of a control circuit. Fig. Figure 7 is a block diagram of a sophisticated audio processor. Fig. Figure 8 is a block diagram illustrating selected elements of an audio processor. Summary

[0007] In one example, an audio processor is disclosed comprising: an audio crossover for separating a first frequency band from a second frequency band, the first frequency band having a lower frequency band than the second frequency band; an excursion estimator for estimating a predicted excursion of a low-frequency sound driver from information about the first frequency band; an interpolator for interpolating an adjustment at the second frequency band to compensate for the estimated excursion; and circuitry for supplying the adjusted second frequency to a receiver. Embodiments of the disclosure

[0008] The following disclosure provides many different embodiments or examples for implementing various features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. Further, throughout the present disclosure, reference numerals and / or letters may be repeated among the various examples. This repetition is for the purpose of simplicity and clarity and does not, in and of itself, dictate any relationship between the various embodiments and / or configurations discussed. Different embodiments may have different advantages, and no particular advantage is necessarily required for every embodiment.

[0009] In broad terms, a loudspeaker is an electromechanical system that reproduces sound. The loudspeaker has a horn or diaphragm with a characteristic moving mass, which can be measured in grams, and a characteristic suspension stiffness, which can be measured in newtons per millimeter, for example.

[0010] A sound driver motor causes vibrations of the diaphragm or horn at a given frequency, causing the horn to generate mechanical waves in the air or other transmission medium that are perceived as sound. The sound driver motor may include a powerful magnet and a voice coil that can be excited by electrical inputs. The electrical inputs to the voice coil generate a variable magnetic field that attracts or repels the magnet's field, moving the diaphragm at the desired frequency and producing sound at a selected frequency.

[0011] A fundamental difficulty in loudspeaker design is that different horn sizes are more suitable for producing different frequencies. For example, when reproducing human-perceivable music, it may be necessary to reproduce frequencies in the range of approximately 10 1 Hertz (Hz) up to approximately 104 Hz. Lower frequencies (e.g., in the range of 20 to 500 Hz) are better reproduced by a larger horn displacing a greater acoustic mass. On the other hand, frequencies above 500 Hz, and especially those in the range of 2 to 20 kHz, are better reproduced by a smaller horn operating at the higher frequency.

[0012] The "holy grail" of loudspeaker design is a completely linear response. In other words, a perfect loudspeaker can reproduce the entire range of audible frequencies without distortion. Currently, there is no known loudspeaker driver design that can perfectly reproduce such a broad frequency range. Certain drivers may be optimized for specific frequency ranges, but generally, the more aggressively they are optimized in one area, the more distortion there will be in other areas. To compensate for this reality, many high-end loudspeakers feature separate "woofers" optimized specifically for low- to mid-frequency ranges and separate "tweeters" optimized for the higher frequency ranges.Some loudspeaker systems also have separate mid-range speakers, and in the general case, the human-perceived audio spectrum (or the "range of human hearing" from approximately 20 Hz to approximately 20,000 Hz) can be divided into any number of sub-ranges with specialized sound drivers for each sub-range.

[0013] When speakers provide separate sound drivers, such as separate woofers and tweeters, a wider frequency range of sound reproduction can be realized. In particular, an input audio signal can be split into separate components, with the high-frequency signal routed to the tweeters and the low- to mid-frequency signals routed to the woofers.

[0014] A common configuration for loudspeakers with separate audio sections is a staggered configuration. For example, a loudspeaker cabinet might have a large woofer with an axially offset tweeter. Although this results in a more linear frequency response across the range of human hearing, it also creates a disadvantage. Ideally, from the perspective of a human user, the sound would appear to be radiating from a single point source. When the speakers are staggered, the sound is not perceived as radiating from a single point source, and thus, despite the wider response, the human user will still hear distortion in the reproduced sound.

[0015] There are several solutions to this problem. One solution is a concentric, or coaxial, speaker configuration. In this configuration, a separate tweeter is placed in the center of a larger woofer. Although the woofer and tweeter still independently produce their own audio frequency ranges, because they are concentric, the audio appears more like it radiates from a single point. Another solution is to simply have a single sound driver. This again achieves the single point source goal more accurately than the staggered speaker configuration, but at the cost of producing the entire frequency range.

[0016] All of the configurations described above—staggered speakers, concentric speakers, and single-driver speakers—are susceptible to what is known as Doppler distortion. The Doppler effect is well-known in both mechanical and electromagnetic wave theory. Very simply put, when a wave source moves toward an observer, the waves appear compressed from the observer's vantage point (shorter waves, higher frequency), with the magnitude of the compression varying directly with the speed at which the wave source approaches. When the wave source moves away from the observer, the waveform appears stretched from the observer's vantage point (longer waves, lower frequency), with the magnitude of the stretch varying directly with the speed at which the wave source moves away from the observer.In electromagnetic wave theory, this is known as "blueshift" for sources of electromagnetic waves moving toward the observer and "redshift" for sources of electromagnetic waves moving away from the observer. In the case of mechanical waves such as sound, the effect is explained in a simple and common way using an ambulance. As an ambulance approaches the observer, the mechanical waves are compressed by the incoming speed of the ambulance, and to the stationary observer, the ambulance siren appears to have a higher pitch until the ambulance reaches the observer. At the exact instant the ambulance reaches the observer, the ambulance siren exhibits no frequency shift, and for that instant the observer hears the siren frequency at its "true" frequency.As the ambulance subsequently moves away from the observer, the frequency of the waveform is stretched proportionally to the speed of the ambulance, and the pitch of the siren appears to drop lower, as the mechanical wave appears to have a lower frequency proportional to the speed of the ambulance.

[0017] In simplest terms, the Doppler effect postulates that when a waveform source is moving relative to an observer, the waveform will experience frequency distortion relative to that observer. This effect comes into play with all loudspeaker types disclosed in this specification.

[0018] In the simple example of a loudspeaker with a single driver designed to reproduce audio across the entire range of human hearing, the diaphragm creates sound waves that are perceptible to a human user. However, the diaphragm creates these sound waves by moving backward and forward. Because the sound source is moving, there is naturally a Doppler effect. In the case of a single-range woofer, the effect is mitigated by the fact that the driver's range of motion is relatively small compared to the wavelength of the bass frequencies. Thus, there is minimal human-perceptible distortion in the bass waveform. In the case of a single-range tweeter, there is also minimal human-perceptible distortion.Although in this case the driver moves backward and forward at a very high frequency, the driver experiences very little displacement, and compared to the displacement of a woofer, this displacement is actually negligible. Thus, there is very little frequency distortion because the driver moves very slightly. However, in the case of a full-range driver, where the driver produces both low frequencies requiring large displacement and superimposed high frequencies, modulation of the higher frequencies can be significant.

[0019] For example, consider a sound driver that reproduces a bass waveform at 20 Hz while also producing a treble waveform at 20 kilohertz (kHz). In other words, for each vibration of the horn to reproduce the 20 Hz signal, the horn will vibrate 1,000 times for the 20 kHz waveform. To simplify the model, consider that the sound driver vibrates 500 times while moving forward to reproduce the treble waveform. It then vibrates 500 times while moving backward to further produce the treble waveform, and then continues this motion backward and forward. In this case, half of the treble waves are perceived as having a higher pitch and half as having a lower pitch than that of the electrical excitation.This can be perceptible to a human because the displacement of the speaker to produce the low-frequency waveform is much greater than the displacement of the speaker to produce the high-frequency waveform. This causes a significant Doppler shift in the high-frequency waveform, which can result in significant, human-perceptible distortion in the high-frequency signal.

[0020] Although the mechanisms are different, there is also human-perceptible distortion in the case of a concentric speaker or a staggered speaker.

[0021] In the case of concentric speakers, the woofer and the tweeter act independently of each other, even though they are coaxial with respect to each other. Thus, the tweeter does not move back and forth with the woofer while the woofer generates its bass waveform. However, since the woofer surrounds the tweeter, the waveform of the tweeter is reflected by the horn of the woofer. This reflection alone can cause distortion, but the distortion is amplified when the surface from which the frequencies are reflected itself moves. A similar result can occur in the case of offset speakers. Although the speakers are not coaxial with respect to each other in that case, it can still be expected that a portion of the high - frequency waveform is reflected by the moving woofer, causing distortion.

[0022] The present description focuses primarily on a method and control circuit for compensating for Doppler distortion in coaxial or offset loudspeakers, where a separate high-frequency sound driver ("a tweeter") generates a waveform that can be reflected from the moving surface of a low-frequency sound driver ("a woofer"). This may include the use of a crossover network that identifies a split between the two signal groups. The teachings of the present description illustrate an example in which two independent sound drivers, specifically a mid-to-low-frequency loudspeaker and a tweeter, are used. A crossover point in such a system is generally at a frequency somewhere between 10 2 and 10 3Hz, usually in the range of 1 to 3 kHz. Typically, there is a relatively sharp roll-off in the response of each sound driver in this crossover frequency range, and the input audio signal is split at this crossover frequency. Sounds below the crossover frequency are fed to the woofer, while sounds higher than the crossover frequency are fed to the tweeter. It should be noted that in more complicated systems that have more sound drivers for more audio ranges, multiple crossover frequencies may be identified and the input audio signal may be further split. The woofer signal can be fed directly to the woofer without any modification or conditioning, at least not with respect to Doppler distortion. Other signal conditioning may be applied, such as active noise reduction.The high-frequency component is not fed directly to the tweeter; instead, information from the low-frequency component is first used to predict the distortion that the tweeter will experience due to the Doppler effect. The high-frequency signal is then conditioned to compensate for this Doppler distortion before being fed to the tweeter. For example, if the movement of the woofer is expected to shift the perceived frequency of the tweeter waveform by 500 Hz, the frequency fed to the tweeter can be reduced by 500 Hz to compensate for the predicted change. In some cases, a time shift can also be applied to the high-frequency audio signal to compensate for misalignment of the acoustic centers of the sound drivers or accelerations that may be caused by reflections from the woofer.

[0023] In the case of coaxial or offset loudspeakers described here, the high-frequency tweeter waveforms are modulated by their reflection from the woofer driver. One method for compensating for this modulation, as described here, is to use a software model of the existing crossover circuit to identify tweeter waves reflected from the bass horn. This may also involve using a physical model of the loudspeaker itself. For example, the physical model may incorporate the size and location of the various sound drivers in the loudspeaker system. It should be noted that in existing loudspeaker systems with separate woofers, tweeters, and possibly mid-range speakers, a crossover circuit may already be in place, which may be a two-way or three-way crossover circuit, to separate the audio signal into two or three components, respectively.A software model for this crossover can be used to model how the frequencies will interact with each other in the known loudspeaker system. In particular, the tweeter driver can be provided with information about the high-frequency signal and its expected interaction with the woofer. A pre-distortion can be inserted into the signal to the tweeter driver with the intended effect of suppressing or attenuating the reflected high-frequency waves.

[0024] A system and method for providing Doppler compensation in coaxial and offset loudspeakers will now be described with more particular reference to the accompanying figures. It should be noted that certain reference numerals may be repeated throughout the figures to indicate that a particular device or block is entirely or substantially consistent across the figures. However, this is not intended to imply any particular relationship between the various disclosed embodiments. In certain examples, a genus of elements may be designated by a particular reference numeral ("thing 10"), while individual individuals of the genus or examples of the genus may be designated by a hyphenated reference numeral ("first specific thing 10-1" and "second specific thing 10-2").

[0025] Fig. 1A is an external perspective view of a loudspeaker 100 that may be configured with coaxial or concentric sound drivers. Loudspeaker 100 represents a class of loudspeakers that may include coaxial or concentric sound drivers, or in some cases, a single sound driver. For the purposes of the examples provided in the present description, loudspeaker 100 represents an embodiment that includes a separate coaxial woofer and tweeter.

[0026] In this example, the loudspeaker 100 is enclosed within an enclosure 104. The enclosure 104 may be constructed from any suitable rigid material, such as plastic, wood, metal, or another rigid material. The enclosure 104 provides physical structure for the loudspeaker 100 and also provides acoustic volume behind the sound drivers. Enclosed within a surface of the enclosure 104 is a sound driver having an edge suspension 110 surrounding the sound driver.

[0027] A tweeter horn 108 is illustrated, as well as a woofer diaphragm 116. In the case of coaxial or concentric speakers, multiple diaphragms may be nested, as in Fig. 2A. A dust cover may cover the voice coil and motor to prevent dust or other contaminants from entering the system.

[0028] Loudspeaker 100 is illustrated with a bass reflex port 112. This bass reflex configuration is popular in contemporary loudspeaker design because it provides a fuller and deeper bass experience. Bass reflex port 112 provides a Helmholtz resonance for the low-frequency sound driver of loudspeaker 100. A Helmholtz resonator utilizes a mass of air to provide greater acoustic output at low frequencies.

[0029] The area within the enclosure 104 provides an acoustic volume that is vented through the bass reflex port 112. The bass reflex port 112 may be connected to a tube or conduit, which may typically have a circular or rectangular cross-section. The mass of the air and the "elasticity" of its inertia form a mechanical resonance, thus providing a Helmholtz resonance at selected bass frequencies. This increases the bass response of the sound driver and can extend the frequency response of the sound driver / enclosure combination to frequencies below the range the sound driver could reproduce in a sealed box.

[0030] Fig. Figure 1B is an external perspective view of a loudspeaker 101 that may be configured for use with offset sound drivers. The loudspeaker 101 is similar to the loudspeaker 100 of Fig. 1A. For example, loudspeaker 101 includes an enclosure 118 and bass reflex ports 128-1 and 128-2, respectively. This embodiment also includes an offset, horn-equipped tweeter 120 that is not coaxial or concentric with woofer 124.

[0031] As discussed above, each of these configurations can result in modulation, in particular modulation of the high-frequency waveforms from the tweeter as they are reflected by the moving woofers. Not only does the reflection itself cause modulation or distortion, but because the woofer experiences very large excursions compared to the tweeters, the moving surface of the woofer causes an acceleration of the reflected high-frequency waveforms. This can be perceived by a human user who is exposed to the speaker 100 from Fig. 1A or speaker 101 Fig. 1B, will experience significant distortion. This distortion of the high-frequency waveforms can lead to a somewhat unpleasant listening experience, with the high frequencies sounding slanted and / or out of tune with respect to the midrange and bass waveforms. As discussed above, it is therefore desirable to provide pre-modulation, which can help limit the effect of the distortion on the audio waveforms.

[0032] Fig. 2A and Fig. 2B illustrate two embodiments of coaxial loudspeaker designs, while Fig. 2C illustrates a non-concentric woofer.

[0033] Fig. Figure 2A is a perspective view of a coaxial speaker system 200, particularly a woofer with a concentric compression tweeter. The coaxial speaker system 200 includes independent coaxial tweeter and woofer sound drivers.

[0034] The coaxial speaker system 200 includes a mid-to-low frequency driver (woofer) with a tweeter driver (compression tweeter 204) nested within the woofer. The two drivers operate independently of each other, providing separate bass and high frequency ranges. The concentric configuration helps provide a better approximation of the acoustic ideal of a point source in free space.

[0035] In this configuration, the compression tweeter 204 includes a magnet 220 driven by a voice coil 212. The voice coil 212 induces a magnetic field in the magnet 220, which drives the compression tweeter 204, which is covered by a tweeter horn 236 to increase the dispersion of the tweeter.

[0036] The remainder of the speaker system 200 provides the woofer for mid-to-low frequencies. The speaker system 200 also includes conventional elements such as a back plate 216, a cover plate 224, a basket 228, a spider 240, a horn 232, an edge mount 244, and a gasket 248.

[0037] Audio sources such as the Concentric Sound Driver 200 radiate pressure waves omnidirectionally with steradians of 4π. The pressure waves radiate as compression and rarefaction of the acoustic medium. This phenomenon occurs in any acoustic medium containing sound waves in air, water, other liquids, and other media.

[0038] Most sound sources exhibit a complex, three-dimensional radiation pattern as a function of frequency. Objects and surfaces in the vicinity of the sound source also produce reflections and refraction effects that disrupt or distort the sound wave. In particular, in the case of a loudspeaker in air, the motion is primarily that of a piston. However, because the wavelength can be very large or very small relative to the piston, the piston's motion influences the radiation pattern.

[0039] As the horn or diaphragm moves forward, the diaphragm increases the pressure in front of the horn (compression) and decreases the pressure behind the horn (rarefaction). For a driver operating at frequencies whose wavelength is large relative to the size of the horn, the positive and negative pressures cancel when measured at a distance. Therefore, loudspeakers are usually housed in an enclosure that isolates the front and rear of the radiating surface. This surface, which is coplanar with the driver, is called the "baffle." Diffraction effects from the edges of a confined baffle alter the radiation pattern.

[0040] For example, the front surfaces of the loudspeaker 100 form Fig. 1A and loudspeaker 101 Fig. 1B a baffle for their respective speakers.

[0041] Unlike in free air, a loudspeaker driver radiates into half-space (steradians of 2π) within a theoretically unbounded baffle. All the radiation that the driver would otherwise project rearward (e.g., behind its moving piston) is reflected back through the plane of the baffle toward the front. The woofer radiates at wavelengths considerably larger than its piston. Therefore, there is significant reflected radiation at and below frequencies corresponding to wavelengths on the order of the size of the radiating area. For a woofer, for example, the wavelength of a 50 Hz tone in air at room temperature is approximately 20 feet, which is more than an order of magnitude larger than most woofer diameters.In contrast, tweeters typically reproduce sound in the approximate range of 2 kHz with a wavelength of approximately 6 inches to 20 kHz with a wavelength of approximately 0.75 inches. The wavelengths produced by tweeters are therefore similar in size to those of the woofer.

[0042] If a loudspeaker driver is mounted in a moving baffle, as in the case of a coaxial tweeter mounted in a woofer, the driver's radiation reflected from the baffle will be subject to the Doppler effect. If the baffle moves in a sinusoidal motion with frequency f 1 and the sound driver, which is mounted in the baffle, moves in a sinusoidal motion with the frequency f 2 moved, the resulting pressure waves exhibit modulation tones at f 2 ± n × f1 where n is a positive integer 1, 2, 3, and so on.

[0043] Any loudspeaker with a separate woofer and tweeter will exhibit this effect to some extent. When a tweeter is mounted adjacent to a woofer, the woofer represents a portion of the baffle in which the tweeter is mounted, producing a predictable and measurable amount of intermodulation. However, this effect is small under normal circumstances because only a distant portion of the baffle is moving. The effect is therefore also small relative to other distortion mechanisms. However, when the tweeter is mounted closer to the woofer, and especially when the tweeter is mounted coaxially with the woofer, the effect becomes more significant.

[0044] In the extreme case of a coaxially mounted tweeter, distortion can be severe. In a coaxial or concentric driver configuration, the tweeter output radiates from the center of a larger woofer or midrange driver in one of several arrangements, such that the moving piston of the lower-frequency driver serves as the baffle of the higher-frequency driver.

[0045] Concentric or coaxial drivers are widely used despite their well-known distortion artifacts. An important attribute is that the acoustic center of the drivers is the same, assuming the two drivers are time-aligned. Because natural sound sources radiate all frequencies from a single point in space, this configuration better approximates real-world sound. Having separate loudspeaker drivers for different frequencies, such as separate woofers, midrange speakers, and tweeters, is sometimes necessary because current loudspeaker drivers have deficiencies in overcoming these Doppler shifts and other distortions.

[0046] Ideally, a single loudspeaker driver could reproduce frequencies across the entire audible spectrum. Because this is technically impossible with current loudspeaker technology, coaxial drivers mix transducers capable of producing different frequency ranges and arrange them together in space in such a way that the constructive and destructive spatial interference of the sound waves generated in the crossover region is eliminated. This can be very effective and produces an excellent acoustic image. However, this same configuration represents the worst-case scenario for Doppler modulation of the tweeter by the woofer.

[0047] Existing systems have used various mechanical arrangements of woofer and tweeter drivers to create coaxial drivers. Some use a compression driver mounted behind the woofer, which radiates through the pole piece either into a horn or using the woofer cone itself as a horn. Other designs use a small tweeter mounted directly on the woofer's pole piece. In all cases, the woofer effectively acts as a baffle for the tweeter, and intermodulation results. At smaller woofer excursions, Doppler distortion can give the speaker a muddy sound. At larger woofer excursions, the effect can be clearly audible and dissonant.

[0048] A secondary factor is that the horn acts as a horn for the tweeter when the tweeter is placed at the throat of the woofer. Normally, the woofer and tweeter would move together in the crossover region, and their pressure output would behave additively. However, because the transition from the tweeter to its horn changes with the movement of the tweeter, an additional amplitude modulation (AM) effect can occur. In summary, large movements of the woofer create the effect of a moving baffle for the tweeter, resulting in Doppler modulation. This is most audible when the woofer produces relatively low frequencies and has a high excursion, and the tweeter produces frequencies above the crossover region where there is little contribution from the woofer.Additionally, in some configurations, woofer movement can modulate the horn transition, producing AM distortion. This is most pronounced at high woofer excursions.

[0049] Most loudspeakers do not have a means to track the position of the woofer. However, it is possible to do so, either by modeling and predicting the horn position or by directly or indirectly measuring the position of the woofer's horn. If the position of the woofer's horn is known, it is possible to use signal processing to reverse the modulation effects of the woofer on the tweeter.

[0050] The present disclosure provides a mechanism for tracking or predicting the motion of the radiating surface of a woofer driver and canceling its intermodulation effect. Furthermore, signal processing can be performed on the motion information, and the signal that would be sent as an input to the tweeter can be modified. A modified signal can be generated for one or both of the drivers to compensate for the Doppler effect and / or other modulation.

[0051] In various embodiments, the motion of the woofer can be sensed either with a physical sensor or predicted using modeling and electrical feedback. The tweeter driver can be mounted in front of the woofer driver, at the throat of the driver, behind the driver, or adjacent to the driver (i.e., offset or non-coaxial). The teachings of the present disclosure apply to all of these configurations and can reduce modulation distortion in each case.

[0052] The signal processing used to carry out the teachings of the present description may be analog, digital, or a combination of both.

[0053] Fig. Figure 2B is a block diagram of a concentric speaker system 201, specifically a woofer with a concentric conventional tweeter. This speaker operates in a similar manner to the speaker system 202 of Fig. 2C. A magnet 222 is driven by a voice coil 214. The voice coil 214 receives electrical signals and induces a magnetic field in the magnet 222. This drives the horn 234, which acts as a piston to reproduce audio sounds. There is also a tweeter motor 206 to reproduce tweeter audio signals. Other conventional elements include a pole piece 210, a cover plate 226, a basket 230, a spider 238, a rim hanger 242, and a gasket 246.

[0054] Fig. Figure 2C is a block diagram illustrating a standalone woofer 202 that can be used in configurations where the woofer and tweeter are offset from each other. It should be noted that in the example of Fig. 2C, separate woofers and tweeters are not shown. Instead, the configuration of woofer 202 can be designed to suit a woofer, tweeter, mid-range speaker, or other sound driver by varying well-known parameters such as the sizes or characteristics of the various elements.

[0055] In this case, the woofer 202 includes a magnet 262 driven by a voice coil 250. The voice coil 250 receives electrical input signals and induces a magnetic field in the magnet 262. This drives the horn 274, which acts as a piston to reproduce audio sounds. Other conventional elements include a pole piece 254, a back plate 258, a cover plate 266, a basket 270, a spider 278, an edge suspension 282, and a gasket 286.

[0056] In configurations where the separate woofers and tweeters are not made of Fig. 2A are mounted coaxially, multiple sound drivers designed for various frequency ranges can be arranged in the entire loudspeaker system. Such a configuration is used in the loudspeaker 101 of Fig. 1B illustrates.

[0057] Fig. Figure 3 contains a schematic representation 300 of an electrical model of a loudspeaker system. One of the most common types of loudspeakers in use today is the dynamic loudspeaker. When the input from an audio speaker is applied as an alternating current to the voice coil, the voice coil and the constant magnetic field created by a permanent magnet surrounding the voice coil are moved by an electromagnetic force. The diaphragm attached to the voice coil pushes the air, creating sound waves. This type of loudspeaker can be reasonably well modeled using the second-order lumped-element, one-degree-of-freedom (SDOF) system illustrated in schematic representation 300.

[0058] In this model, the relationship between the applied voltage and the resulting current can be expressed in a closed form as follows: vc(s)ic(s)=Re+sLe(x)+Bl(x)2s2Mms+sRms+Kms(x)

[0059] It should be noted that for simplicity, this equation applies to a woofer alone and does not include additional terms for a sealed enclosure. A sealed enclosure may introduce additional terms that may need to be modeled according to the specific design of the sealed enclosure.

[0060] Loudspeakers are, of course, housed in an enclosure, and the above model is valid for this sealed enclosure. Enclosures with an opening or vent, such as a bass reflex port, may require additional elements in the model to replicate the behavior of the loudspeaker. Such models are well known, and for the purposes of the present disclosure, and for the simplicity of the model disclosed herein, the present model does not include an expression for a bass reflex port.

[0061] Loudspeaker nonlinearity is typically modeled by a variation of BI, Kms, and Le depending on the position of the diaphragm. This can be modeled as displacement polynomials as follows: Bl(x)=Bl0+Bl1∗x+Bl2∗x2+Bl3∗x3+Bl4∗x4Kms(x)=Kms0+Kms1∗x+Km s2∗x2+Kms3∗x3+Kms4∗x4Le(x)=Le0+Le1∗x+Le2∗x2+Le3∗x3+Le4∗x4

[0062] The principle of linearization is to determine the nonlinear elements of the system and apply equalization algorithms to the audio signal to pre-perturb the signal and linearize the nonlinearity of the loudspeaker.

[0063] Fig. Figure 4 is a block diagram of one possible implementation of a linearization subsystem 400. In this case, a nonlinear equalization circuit 420 receives the audio input, drives the audio, and performs linearization equalization on the audio input signal. The equalized audio signal is fed to the audio power amplifier 424, and the audio power amplifier 424 provides the linearized output to the sound driver 404.

[0064] To provide linearization, a loudspeaker model 412 is used to calculate nonlinearities and compensating linearization factors based on the parameter adjustment 408. As discussed above, this can be represented by the following model: vc(s)ic(s)=Re+sLe(x)+Bl(x)2s2Mms+sRms+Kms(x)

[0065] A discrete-time model of the system can be derived from the continuous-time model using a bilinear transformation. For example, a second-order infinite-response (IIR) system can be used to model the linear behavior of the system, and continuous real-time adaptation can be implemented to track changes over time and device fluctuations. A state-space model can be used to describe the system with a set of first-order differential equations and can provide a means for discrete-time modeling of the loudspeaker from the continuous-time model. An advantage of the state-space model is the ability to apply nonlinear behaviors to key loudspeaker parameters.A linear discrete time model can be used to fit the linear parameters and the nonlinear state space model can be used to predict and compensate for the nonlinear behavior.

[0066] These nonlinear coefficients can be described in a laboratory setup, for example, to measure deflections with lasers. They do not need to be updated by an adaptive filter. However, there is a possibility to update the nonlinear parameters in-situ based on feedback voltage and current.

[0067] Fig. Figure 5 is an illustration of a modulation of an acoustic waveform. This figure illustrates the concept of Doppler distortion. Doppler distortion can occur when a high-frequency sound is reflected from a moving baffle, such as a woofer coaxial with a tweeter. For example, a 2 kHz sound may be reflected from a vibrating baffle, producing a sound at 80 Hz. The low-frequency sound results in a significant degree of excursion of the woofer driver, while the excursion of the tweeter driver is relatively negligible.

[0068] In this illustration, loudspeaker 504 produces a 2 kHz tone that is reflected by a baffle vibrating at 80 Hz. This results in waveform 508, which shows that modulations are introduced into the 2 kHz signal.

[0069] The movement of the baffle causes a periodic time shift, which in the perception of a human user periodically moves the apparent point source of the sound at 2 kHz backwards and forwards.

[0070] The sound of the 2 kHz signal when modulated by a baffle at 80 Hz can be expressed as follows: y(t)=A2KHzcos(2πf2KHz(t+cos(2πf80KHzt)∗AexcursionVsound))

[0071] Aexcursion is the peak excursion of the baffle at 80 Hz, and Vsound is the speed of sound (approximately 340 meters per second in room temperature air).

[0072] With this example loudspeaker, the peak excursion for an audio signal of -60 decibels (dB) is 2.73 mm, which translates into a time delay of 8 microseconds (µs).

[0073] Doppler distortion can be corrected by isolating the high-frequency and low-frequency signals with a crossover filter in a digital signal processor (DSP) and compensating for the time shift on the high-frequency sound. This can be accomplished by altering the high-frequency sound, which is particularly useful in the case of concentric sound drivers, where essentially all of the sound can be modulated by the vibrating baffle. In cases with offset speakers, it may be more appropriate to suppress the reflected waveforms because, even if that reflected by the low-frequency speaker is suppressed, a large percentage of the waveform generated by the tweeter still reaches the user.

[0074] Fig. 6 is a block diagram of a control circuit 600. The control circuit 600 includes a crossover network 604. The crossover network 604 may already be present in the system, as crossover networks are generally required for speaker systems that drive separate woofers, tweeters, or other limited-spectrum sound drivers. The crossover network 604 may be either an active crossover network or a passive crossover network and may include a two-way network, a three-way network, or other crossover network. In general, the crossover network 604 may be an n-way crossover network and may be implemented either actively or passively. Further, the crossover network 604 may include software and / or hardware. In this embodiment, a passive crossover network splits the audio signal after it has been amplified by a single power amplifier.In an active speaker system, the crossover comes before the amplifiers, and an amplifier is required for each sound driver.

[0075] The amplified signal is then sent to one or more types of sound drivers, each representing a different frequency range. An active crossover network uses active components in the filters. Active crossover networks can use active devices such as operational amplifiers and can operate at levels suitable for power amplifier inputs.

[0076] The crossover network 604 provides a high-frequency signal and a low-frequency signal. The low-frequency signal can be fed directly to a low-frequency sound driver 616. The high-frequency signal is provided to an adjustable delay block 612. The excursion estimator 608 receives the low-frequency signal information and estimates the excursion of the low-frequency sound driver, which provides the moving baffle for the high-frequency signal. The adjustable delay block 612 estimates an adjustable delay for the high-frequency signal to compensate for the movement of the low-frequency baffle. This signal is then fed to the high-frequency sound driver 614. The sound from the HF sound driver 614 and the LF sound driver 616 mix in the air and appears to the listener as a single audio signal.

[0077] It should be noted that this example illustrates an embodiment in which the high-frequency signal is adjusted to compensate for the movement of the low-frequency sound driver, which acts as a baffle for the high-frequency output. This is not possible in all cases. In other cases, an adjustable delay 612 may be inserted into the low-frequency sound driver 616. This serves to suppress the distorted sound of the audio reflected from the LF sound driver 616. Such a configuration may be particularly suitable in a case where the speakers are not concentric and where it is desired to completely suppress the distorted audio of the reflection.In cases of concentric or coaxial sound drivers, it may not be appropriate to suppress the entire reflected signal, and instead, it may be desirable to build an equalization factor such that the reflected signal appears to the end user as an undistorted audio signal. This can be achieved by inserting the adjustable delay into the RF sound driver 614.

[0078] Fig. 7 is a block diagram of a sophisticated audio processor 700. The sophisticated audio processor 700 may be an embodiment of a speaker system or any other suitable circuit or structure.

[0079] The sophisticated audio processor 700 includes a sound driver 730 that outputs the actual audio waveform to the user for listening. It should be noted that the sound driver 730 is illustrated here as a sound driver of a sophisticated audio processor 700, but could be any suitable sound driver for sinusoidal waveforms. This could be an audio sound driver, a mechanical sound driver, or an electrical signal sound driver. Likewise, the sophisticated audio processor 700 should be understood as a non-limiting example, although it is provided as an illustrative application of the teachings of the present description. Other applications include, by way of illustrative example, home entertainment system speakers, portable speakers, concert speakers, a mobile phone, a smartphone, a portable MP3 player, any other portable music player, a tablet, a laptop, or a portable video device.Non-entertainment applications may include a device used in medicine, a device used for communication, a device used in a manufacturing context, a pilot's headset, an amateur radio device, any other type of radio device, a studio monitor speaker, a music or video production device, a dictaphone, or any other device to enable the electronic transmission of audio signals.

[0080] In the remaining description for Fig. 7, it is assumed that the teachings here are implemented in a sophisticated audio processor 700.

[0081] The sophisticated audio processor 700 includes an audio jack 708 used to receive a direct analog audio input. In cases where an analog audio input is received, the analog data is provided directly to the signal processor 720, and signal processing is performed on the audio. It should be noted that this may include converting the signal to a digital format, as well as encoding, decoding, or otherwise processing the signal. It should be noted that in some cases, the signal processing is performed in the analog domain rather than the digital domain.

[0082] In some cases, the sophisticated audio processor 700 also includes a digital data interface 712. The digital data interface 712 may be, for example, a USB, Ethernet, Bluetooth, or other wired or wireless digital data interface. When digital audio data is received at the sophisticated audio processor 700, the data cannot be directly processed in the analog domain. Thus, in that case, the data may be provided to an audio encoder / decoder 716, which may provide encoding and decoding of audio signals and, in some cases, convert analog domain audio data to digital domain audio data that may be processed in the digital domain at the signal processor 720.

[0083] Fig.Figure 8 is a block diagram illustrating selected elements of an audio processor 800. The audio processor 800 is an example of a circuit or application that may benefit from the teachings of this specification, including the coaxial and offset speakers described herein.

[0084] Only selected elements of the audio processor 800 are shown here. This is for simplicity of the drawing and to illustrate applications for certain components. The use of certain components in this figure is not intended to imply that those components are necessary, and the omission of certain components is not intended to imply that those components must be omitted. Furthermore, the blocks shown here are generally functional in nature and may not always represent discrete or precisely defined circuits. In many electronic systems, various components and systems provide feedback and signals to one another, such that it is not always possible to determine exactly where one system or subsystem ends and another begins.

[0085] As an illustrative example, audio processor 800 includes a microphone offset generator 808 that generates a DC offset for a microphone input. This is for an embodiment that includes both a microphone and a speaker, such as a headset, and microphone offset generator 808 helps ensure that the microphone is operating at the correct voltage.

[0086] A power manager 812 provides power conditioning, a constant voltage supply such as a DC output voltage, and power distribution to other system components.

[0087] A low-dropout (LDO) voltage regulator 816 is a voltage regulator that helps ensure that correct voltage is provided to other system components.

[0088] A phase-locked loop (PLL) 840 and a clock oscillator 844 may together provide mclk, the local clock signal for operation in the circuit. It should be noted that the PLL 840 may also be a simple analog PLL of a more traditional design, although it may be a filterless digital PLL.

[0089] An analog-to-digital converter (ADC) input modulator 824 receives a signal from an analog audio source and generates an output signal that is transmitted simultaneously with a signal from the digital microphone input 804.

[0090] An I / O signal routing 836 provides signal routing between various components of the audio processor 800. The I / O signal routing 836 provides a digital audio output to the digital-to-analog converter (DAC) 864, which converts the digital audio to analog audio and then supplies the analog audio to the output amplifier 870, which supplies the audio waveform to a sound driver.

[0091] A DSP core 848 receives input / output signals and provides audio processing. The DSP core 848 may include, by way of illustrative and non-limiting example, biquad filters, limiters, volume controls, and audio mixing. Audio processing may include encoding, decoding, active noise reduction, audio amplification, and other audio processing techniques. A control interface 852 is provided for controlling internal functions, which in some cases are user-selectable. The control interface 852 may also provide a self-start function.

[0092] The audio processor 800 also includes asynchronous sample rate converters (ASRCs) 860-1 and 860-2, which in some cases may be bidirectional ASRCs. A bidirectional ASRC includes both an input ASRC and an output ASRC and may include distinct embodiments of an ASRC. The ASRCs 860-1 and 860-2 may, in some examples, include one or more filterless digital PLLs. The ASRCs 860-1 and 860-2 also include serial I / O ports 856-1 and 856-2, respectively, which enable the ASRCs 860-1 and 860-2 to communicate with external systems.

[0093] It should be noted that the operations discussed above with reference to the figures are applicable to any integrated circuit that includes audio signal processing and may further be combined with circuits that perform other types of signal processing (e.g., hand gesture signal processing, video signal processing, audio signal processing, analog-to-digital conversion, digital-to-analog conversion), particularly those that can execute specialized software programs or algorithms, some of which may be associated with processing digitized real-time data. Certain embodiments may relate to multi-DSP, multi-ASIC, or multi-SoC signal processing, floating-point processing, signal / control processing, fixed function processing, microcontroller applications, etc.In certain contexts, the features discussed herein may be applicable to audio headphones, noise-cancelling headphones, earphones, studio monitor speakers, computer audio systems, home theater audio, concert speakers, and other audio systems and subsystems. The teachings herein may also be combined with other systems or subsystems, such as medical systems, scientific instrumentation, wireless and wired communications, radar, industrial process control, audio and video equipment, power sensing, instrumentation (which may be highly accurate), and other digital processing-based systems.

[0094] Additionally, certain embodiments discussed above may be provided in digital signal processing technologies for audio and video equipment, medical imaging, patient monitoring, medical instrumentation, and home healthcare. This could include, for example, lung monitors, accelerometers, heart rate monitors, or pacemakers, along with peripherals therefor. Other applications may include automotive technologies for safety systems (e.g., stability control systems, driver assistance systems, braking systems, infotainment, and interior applications of any kind). Furthermore, engine / driveline systems (e.g., in hybrid and electric vehicles) may utilize high-fidelity data conversion, playback, and display products in battery monitoring, control systems, message controls, maintenance operations, and others.In still further example scenarios, the teachings of the present disclosure may be applicable in industrial markets that include process control systems that help advance productivity, energy efficiency, and reliability. In consumer applications, the signal processing circuit teachings discussed above may be used for image processing, autofocus, and image stabilization (e.g., for digital still cameras, camcorders, etc.). Other consumer applications may include audio and video processors for home theater systems, DVD recorders, and high-definition televisions. Still other consumer applications may include sophisticated touchscreen controllers (e.g., for any type of portable media device). Therefore, such technologies could readily be incorporated into smartphones, tablets, security systems, PCs, gaming technologies, virtual reality, simulation training, etc. Example implementations

[0095] The following examples are provided for illustrative purposes.

[0096] In one example, an audio processor is disclosed comprising: an audio crossover for separating a first frequency band from a second frequency band, the first frequency band having a lower frequency band than the second frequency band; an excursion estimator for estimating a predicted excursion of a low-frequency sound driver from information about the first frequency band; an interpolator for interpolating an adjustment at the second frequency band to compensate for the estimated excursion; and circuitry for supplying the adjusted second frequency to a receiver.

[0097] Further, an exemplary audio processor is disclosed wherein the receiver is a tweeter driver.

[0098] An exemplary audio processor is further disclosed, further comprising circuitry for supplying the first frequency to a low-frequency sound driver.

[0099] Further, an exemplary audio processor is disclosed, wherein the interpolation device includes logic to calculate a Doppler compensation for the reflection of audio waveforms of the high frequency sound driver from the low frequency sound driver.

[0100] Further, an exemplary audio processor is disclosed, wherein the interpolation device comprises a mathematical model of a loudspeaker system comprising the audio processor.

[0101] Further disclosed is an exemplary audio processor wherein the speaker system model comprises a concentric speaker system wherein a high frequency sound driver is concentric with a low frequency sound driver.

[0102] Further, an exemplary audio processor is disclosed, wherein the interpolation device is operable to calculate an audio waveform to suppress high frequency waveforms reflected from the moving low frequency sound driver.

[0103] Further disclosed is an exemplary audio processor wherein the speaker system model comprises a staggered speaker system wherein a high frequency sound driver is offset from a low frequency sound driver.

[0104] Further, an exemplary audio processor is disclosed, wherein the interpolation device is operable to calculate an audio waveform to suppress high frequency waveforms reflected from the moving low frequency sound driver.

[0105] An exemplary audio processor is further disclosed, further comprising a linearization subsystem.

[0106] Further, an exemplary audio processor is disclosed, wherein the linearization subsystem comprises a loudspeaker model in a feedback loop with a nonlinear equalizer.

[0107] Furthermore, an exemplary audio processor is disclosed, further comprising circuitry for supplying the first frequency unchanged to a low-frequency sound driver.

[0108] Further disclosed is an exemplary integrated circuit comprising the audio processor of several of the above examples.

[0109] Further disclosed is an exemplary on-chip system including the audio processor of several of the above examples.

[0110] Further disclosed is an example of a single electronic circuit comprising the audio processor of several of the above examples.

[0111] Also disclosed is an exemplary speaker system comprising: a woofer; a tweeter; and an audio processing circuit configured to: separate a low frequency band from a high frequency band; estimate an expected excursion of the woofer in response to the low frequency band from the low frequency band; calculate an adjustment at the high frequency band to suppress reflection of a high frequency audio signal of the tweeter from the woofer moving at the estimated excursion; supply the low frequency band to the woofer sound driver; and supply the adjusted high frequency band to the tweeter.

[0112] Further, an exemplary loudspeaker system is disclosed, wherein the audio processor circuit is configured to supply the low frequency band to the woofer without adjustment.

[0113] Further, an exemplary loudspeaker system is disclosed, wherein the audio processor circuit is further configured to calculate a Doppler compensation for the reflection of audio waveforms of the tweeter sound driver from the woofer sound driver.

[0114] Further, an exemplary loudspeaker system is disclosed, wherein the audio processor circuit provides a mathematical model of the loudspeaker system.

[0115] Further, an exemplary loudspeaker system is disclosed wherein the tweeter is concentric with the woofer.

[0116] Further, an exemplary loudspeaker system is disclosed, wherein the audio processor circuit is configured to calculate an audio waveform to suppress high frequency waveforms reflected from the moving woofer.

[0117] Further, an exemplary loudspeaker system is disclosed, wherein the audio processor circuit is configured to calculate an audio waveform to suppress high frequency waveforms reflected from the moving woofer.

[0118] Further, an exemplary loudspeaker system is disclosed, wherein the audio processor circuit includes a linearization subsystem.

[0119] Further, an exemplary loudspeaker system is disclosed, wherein the linearization subsystem comprises a loudspeaker model in a feedback loop with a nonlinear equalizer.

[0120] Further disclosed is an exemplary method for performing audio processing for a loudspeaker system, comprising: separating a first frequency band from a second frequency band, the first frequency band having a lower frequency band than the second frequency band; estimating a predicted excursion of a low-frequency sound driver from the first frequency band; interpolating an adjustment at the second frequency band to compensate for the predicted excursion; and supplying the adjusted first frequency band to a high-frequency sound driver.

[0121] An exemplary method is further disclosed, further comprising supplying the first frequency to a low frequency sound driver.

[0122] Further, an exemplary method is disclosed, wherein interpolating comprises calculating a Doppler offset for the reflection of waveforms of the high frequency sound driver from the low frequency sound driver.

[0123] An exemplary method is further disclosed, further comprising calculating a mathematical model of the loudspeaker system.

[0124] Further, an exemplary method is disclosed wherein the model of the loudspeaker system comprises a tweeter concentric with a woofer.

[0125] Further, an exemplary method is disclosed, wherein interpolating comprises calculating an audio waveform to suppress high frequency waveforms reflected from the moving woofer.

[0126] Further, an exemplary method is disclosed wherein the model of the loudspeaker system includes a tweeter offset from a woofer.

[0127] Further, an exemplary method is disclosed, wherein interpolating comprises calculating an audio waveform to suppress high frequency waveforms reflected from the moving woofer.

[0128] Furthermore, an exemplary method is disclosed, further comprising calculating a linearization for the loudspeaker system.

[0129] Further, an exemplary method is disclosed, wherein calculating the linearization comprises applying a loudspeaker model in a feedback loop with a nonlinear equalizer.

[0130] The foregoing outlines features of several embodiments so that those skilled in the art may better understand aspects of the present disclosure. Those skilled in the art should appreciate that the present disclosure may be readily used as a basis for designing or modifying other processes and structures for performing the same objects and / or achieving the same advantages of the embodiments presented herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made therein without departing from the spirit and scope of the present disclosure.

[0131] The particular embodiments of the present disclosure may readily include a system-on-chip (SoC) package for a central processing unit (CPU). An SoC represents an integrated circuit (IC) that integrates components of a computer or other electronic system into a single chip. It may include digital, analog, mixed-signal, and radio frequency functions, all of which may be provided on a single chip substrate. Other embodiments may include a multi-chip module (MCM), wherein multiple chips are arranged in a single electronic package and configured to closely interact with each other through the electronic package.Any module function or block element of an ASIC or SoC may, where appropriate, be provided in a reusable "black box" block of intellectual property (IP block), which may be distributed separately without revealing the logical details of the IP block. In various other embodiments, the digital signal processing functionalities may be implemented in one or more silicon cores in application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and other semiconductor chips.

[0132] In some cases, the teachings of the present description may be encoded in one or more tangible, non-transitory, computer-readable media having executable instructions stored thereon that, when executed, direct a programmable device (such as a processor or DSP) to perform the methods or functions disclosed herein. In cases where the teachings herein are embodied at least partially in a hardware device (such as an ASIC, IP block, or SoC), a non-transitory medium could include a hardware device hardware-programmed with logic to perform the methods or functions disclosed herein.The teachings could also be practiced in the form of a Register Transfer Level (RTL) or other hardware description language such as VHDL or Verilog, which can be used to program a manufacturing process to create the disclosed hardware elements.

[0133] In example implementations, at least some portions of the processing operations outlined herein may also be implemented in software. In some embodiments, one or more of these features may be implemented in hardware external to the elements of the disclosed figures or may be combined in any suitable manner to achieve the intended functionality. The various components may include software (or "reciprocating software") that can coordinate to achieve the operations outlined herein. In still other embodiments, these elements may include any suitable algorithms, hardware, software, components, modules, interfaces, or objects that enable their operations.

[0134] Furthermore, some of the components associated with described microprocessors may be removed or otherwise interconnected. In a general sense, the arrangements depicted in the figures may be rather logical in their representations, while a physical architecture may contain various permutations, combinations, and / or hybrids of these elements. It is imperative to note that countless possible design configurations may be used to accomplish the operational tasks outlined herein. Accordingly, the associated infrastructure will exhibit a myriad of substitute arrangements, design choices, device choices, hardware configurations, software implementations, equipment choices, etc.

[0135] Any suitably configured processor component may execute any type of instructions associated with the data to achieve the operations detailed herein. Any processor disclosed herein could transform an element or item (e.g., data) from one state or thing to another state or thing. In another example, some operations outlined herein may be implemented with fixed logic or programmable logic (e.g., software and / or computer instructions executed by a processor), and the elements identified herein could include some type of programmable processor, programmable digital logic (e.g.,an FPGA, an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM)), an ASIC comprising digital logic, software, code, electronic instructions, flash data storage, optical disks, CD-ROM, DVD-ROM, magnetic or optical cards, or types of machine-readable media suitable for storing electronic instructions, or any suitable combination thereof. In operation, processors may store information in any suitable type of non-volatile storage medium (e.g., random access memory (RAM), read-only memory (ROM), FPGA, EPROM, electrically erasable programmable ROM (EEPROM), etc.), software, hardware, or in any other suitable component, device, element, or object, where appropriate and based on particular requirements.Furthermore, the information tracked, sent, received, or stored in a processor could be provided in any database, register, table, cache, queue, control list, or memory structure based on particular needs and implementations, all of which could be referenced in any suitable timeframe. Each of the data storage elements discussed herein should be considered to be included within the broad term "data storage." Likewise, each of the potential processing elements, modules, and engines described herein should be considered to be included within the broad term "microprocessor" or "processor."Furthermore, in various embodiments, the processors, data memories, network cards, buses, storage devices, associated peripherals, and other hardware elements described herein may be implemented by a processor, data memories, and other associated devices configured by software or firmware to emulate or virtually emulate the functions of those hardware elements.

[0136] Computer program logic that implements all or part of the functionality described herein is embodied in various forms, including, but not limited to, source code form, computer-executable form, hardware description form, and various intermediate forms (e.g., mask products or forms generated by an assembler, compiler, linker, or locator). In one example, source code comprises a set of computer program instructions implemented in various programming languages, such as object code, assembly language, or a high-level language such as OpenCL, RTL, Verilog, VHDL, Fortran, C, C++, JAVA, or HTML, for use with various operating systems or operating environments. The source code may define and use various data structures and communication messages. The source code may be in a computer-executable form (e.g.,via an interpreter), or the source code can be converted into a computer-executable form (e.g. via a translation program, an assembler or compiler).

[0137] In the discussions of the above embodiments, the capacitors, buffers, graphics elements, coupling cards, clocks, DDR, camera sensors, dividers, inductors, resistors, amplifiers, switches, digital cores, transistors, and / or other components may be readily exchanged, replaced, or otherwise modified to accommodate particular circuitry requirements. Furthermore, it should be noted that the use of complementary electronic devices, hardware, non-transitory software, etc., provides an equally viable option for implementing the teachings of the present disclosure.

[0138] In an exemplary embodiment, any number of the electrical circuits of the figures may be implemented on a circuit board of an associated electronic device. The circuit board may be a general-purpose circuit board that may hold various components of the internal electronic system of the electronic device and further provide connectors for other peripheral devices. More specifically, the circuit board may provide the electrical connections through which the other components of the system may electrically communicate. Any suitable processors (including digital signal processors, microprocessors, supporting chipsets, etc.), data storage elements, etc., may be suitably coupled to the circuit board based on particular configuration requirements, processing needs, computer designs, etc.Other components, such as external memory, additional sensors, audio / video display controllers, and peripheral devices, may be attached to the circuit board as plug-in cards, via cables, or integrated into the circuit board itself. In another exemplary embodiment, the electrical circuits of the figures may be implemented as standalone modules (e.g., a device with associated components and associated circuitry configured to perform a particular application or function) or as plug-in modules in application-specific hardware of electronic devices.

[0139] It should be noted that with the numerous examples provided herein, an interaction may be described in terms of two, three, four, or more electrical components. However, this has been done for purposes of clarity and by way of example only. It should be recognized that the system may be interconnected in any suitable manner. Following similar design alternatives, any of the illustrated components, modules, and elements of the figures may be combined in various possible configurations, all of which are clearly within the broad scope of this description. In certain cases, it may be simpler to describe one or more of the functionalities of a given group of operations by referring only to a limited number of electrical elements.It should be recognized that the electrical circuits of the figures and their teachings are readily scalable and can accommodate a large number of components and more complicated / sophisticated arrangements and configurations. Accordingly, the examples provided should not limit the scope or preclude the potential application of the broad teachings of the electrical circuits to a myriad of other architectures.

[0140] Numerous other changes, substitutions, variations, alterations, and modifications may be ascertained by one skilled in the art, and it is intended that this description include all such changes, substitutions, variations, alterations, and modifications as falling within the scope of the appended claims.To assist the United States Patent and Trademark Office (USPTO), and in addition, all readers of any patent issued on this application, in interpreting the claims appended hereto, applicant wishes to state that applicant: (a) does not intend any of the appended claims to invoke 35 USC §112(f) as it exists on the date hereof, unless the words "means of" or "steps of" are particularly used in the applicable claims; and (b) does not intend by any statement in the specification to limit this disclosure in any manner not otherwise recited in the appended claims.

[0141] According to one aspect, in one example, an audio processor is disclosed comprising: an audio crossover for separating a first frequency band from a second frequency band, the first frequency band having a lower frequency band than the second frequency band; an excursion estimator for estimating a predicted excursion of a low-frequency sound driver from information about the first frequency band; an interpolator for interpolating an adjustment at the second frequency band to compensate for the estimated excursion; and circuitry for supplying the adjusted second frequency to a receiver.

Claims

[1] Audio processor (700) comprising: an audio splitter for separating a first frequency band from a second frequency band, the first frequency band having a lower frequency band than the second frequency band; a displacement estimation unit (608) for estimating a predicted displacement of a woofer sound driver (616) from information about the first frequency band; an interpolation device for interpolating an adjustment at the second frequency band to compensate for the estimated displacement; and a circuit arrangement for supplying the adapted second frequency band to a receiver. [2] The audio processor (700) of claim 1, wherein the receiver is a high frequency sound driver (614). [3] The audio processor (700) of claim 2, further comprising circuitry for supplying the first frequency band to a low frequency sound driver (616). [4] The audio processor (700) of claim 3, wherein the interpolation means comprises logic to calculate a Doppler compensation for the reflection of audio waveforms of the high frequency sound driver (614) from the low frequency sound driver (616). [5] Audio processor (700) according to one of the preceding claims, wherein the interpolation means comprises a mathematical model of a loudspeaker system (200) including the audio processor (700). [6] The audio processor (700) of claim 5, wherein the model of the speaker system (200) comprises a system with concentric speakers (100), wherein a high-frequency sound driver (614) is concentric with the low-frequency sound driver (616). [7] The audio processor (700) of claim 5 or 6, wherein the interpolation means is configured to calculate an audio waveform to suppress high-frequency waveforms reflected by the low-frequency sound driver (616). [8] The audio processor (700) of any one of claims 5 to 7, wherein the speaker system model (200) comprises a system with offset speakers (100), wherein a high-frequency sound driver (614) is offset from the low-frequency sound driver (616). [9] The audio processor (700) of claim 8, wherein the interpolation means is configured to calculate an audio waveform to suppress high frequency waveforms reflected by the low frequency sound driver (616). [10] The audio processor (700) of any preceding claim, further comprising a linearization subsystem (400). [11] The audio processor (700) of claim 10, wherein the linearization subsystem (400) comprises a loudspeaker model in a feedback loop with a non-linear equalizer. [12] An audio processor (700) according to any preceding claim, further comprising circuitry for supplying the first frequency band unaltered to a low frequency sound driver (616). [13] An integrated circuit comprising the audio processor (700) according to any one of the preceding claims. [14] An on-chip system comprising the audio processor (700) according to any one of the preceding claims. [15] A discrete electronic circuit comprising the audio processor (700) according to any one of the preceding claims. [16] Loudspeaker system (200) comprising: a woofer (124); a tweeter (120); and an audio processing circuit configured to: Separating a low frequency band from a high frequency band; estimating an expected excursion of the woofer (124) in response to the low frequency band from the low frequency band; calculating an adjustment at the high frequency band to compensate for the reflection of a high frequency audio signal of the tweeter (120) from the woofer (124) moving at the estimated displacement; Feeding the low frequency band to the woofer (124); and Feeding the adjusted high frequency band to the tweeter (120). [17] The loudspeaker system (200) of claim 16, wherein the audio processing circuit is configured to supply the low frequency band to the woofer (124) without adjustment. [18] The loudspeaker system (200) of claim 16 or 17, wherein the audio processing circuit is further configured to calculate a Doppler compensation for the reflection of audio waveforms of the tweeter (120) from the woofer (124). [19] A method for performing audio processing for a loudspeaker system (200), comprising: Separating a first frequency band from a second frequency band, the first frequency band having a lower frequency band than the second frequency band; estimating a predicted excursion of a low-frequency sound driver (616) from the first frequency band; Interpolating an adjustment at the second frequency band to compensate for the predicted deflection; and Feeding the adjusted second frequency band to a tweeter driver (614). [20] The method of claim 19, wherein interpolating comprises calculating a Doppler offset for the reflection of audio waveforms of the high frequency sound driver (614) from the low frequency sound driver (616). [21] The method of claim 19 or 20, further comprising supplying the first frequency band to the woofer sound driver (616). [22] The method of claim 21, further comprising calculating an audio waveform to suppress high frequency waveforms reflected from the low frequency sound driver (616). [23] The method of claim 21, further comprising supplying the first frequency band unaltered to the low frequency sound driver (616). [24] One or more non-transitory computer-readable media having instructions stored thereon, which instructions, when executed by a system, cause the system to: Separating a first frequency band from a second frequency band, the first frequency band having a lower frequency band than the second frequency band; Estimating a predicted excursion of a low-frequency sound driver (616) based at least on information of the first frequency band; Interpolating an adjustment of the second frequency band to compensate for the estimated displacement; and Feeding the adjusted second frequency band to a receiver. [25] The one or more non-transitory computer-readable media of claim 24, wherein the instructions, when executed by a system, cause the system to supply the first frequency band to the low-frequency sound driver (616). [26] The one or more non-transitory computer-readable media of claim 24 or 25, wherein the instructions, when executed by a system, cause the system to calculate a Doppler offset for the reflection of audio waveforms from the receiver reflected by the low-frequency sound driver (616). [27] The one or more non-transitory computer-readable media of any of claims 24 to 26, wherein the instructions, when executed by a system, cause the system to calculate an audio waveform to suppress high-frequency waveforms reflected from the low-frequency sound driver (616). [28] The one or more non-transitory computer-readable media of any one of claims 24 to 27, wherein the instructions, when executed by a system, cause the system to supply the first frequency band unaltered to the low-frequency sound driver (616). [29] One or more non-transitory computer-readable media having instructions stored thereon, which instructions, when executed by a system, cause the system to: Separating a low frequency band from a high frequency band; estimating an expected excursion of a woofer (124) in response to the low frequency band from the low frequency band; calculating an adjustment at the high frequency band to compensate for the reflection of a high frequency audio signal from a tweeter (120) from the woofer (124) moving at the estimated displacement; Feeding the low frequency band to the woofer (124); and Feeding the adjusted high frequency band to the tweeter (120). [30] The one or more non-transitory computer-readable media of claim 29, wherein the instructions, when executed by a system, cause the system to supply the low frequency band to the woofer (124) without adjustment. [31] The one or more non-transitory computer-readable media of claim 29 or 30, wherein the instructions, when executed by a system, cause the system to calculate a Doppler offset for the reflection of audio waveforms of the tweeter (120) from the woofer (124). [32] The one or more non-transitory computer-readable media of any of claims 29 to 31, wherein the instructions, when executed by a system, cause the system to suppress high-frequency waveforms reflected from the woofer (124). [33] The one or more non-transitory computer-readable media of any one of claims 29 to 32, wherein the system comprises the tweeter (120) concentric with the woofer (124). [34] The one or more non-transitory computer-readable media of any of claims 29 to 33, wherein the instructions, when executed by a system, cause the system to calculate an audio waveform to suppress high-frequency waveforms reflected from the woofer (124). [35] The one or more non-transitory computer-readable media of any one of claims 29 to 32 or claim 34, wherein the system comprises the tweeter (120) offset from the woofer (124). [36] The one or more non-transitory computer-readable media of any one of claims 29 to 35, wherein the system comprises two independent drivers and the woofer (124) is a mid-to-low frequency speaker. [37] The one or more non-transitory computer-readable media of any one of claims 29 to 36, wherein a time shift is applied to one or more high-frequency audio signals to compensate for the mismatch of multiple acoustic centers of multiple drivers. [38] The one or more non-transitory computer-readable media of any one of claims 29 to 37, wherein information about one or more high-frequency signals and their expected interaction with the woofer (124) is provided to the tweeter (120). [39] The one or more non-transitory computer-readable media of any one of claims 29 to 38, wherein pre-distortion is inserted into one or more signals to the tweeter (120) to suppress one or more reflected radio frequency waves.

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