CN111193973B

CN111193973B - Dynamic eliminating buzzer of loudspeaker

Info

Publication number: CN111193973B
Application number: CN201911117585.4A
Authority: CN
Inventors: R·波勒罗斯; V·P·尼加姆
Original assignee: Maxim Integrated Products Inc
Current assignee: Maxim Integrated Products Inc
Priority date: 2018-11-15
Filing date: 2019-11-15
Publication date: 2022-07-22
Anticipated expiration: 2039-11-15
Also published as: CN111193973A

Abstract

Implementations describe a method and system to perform the method to reduce buzzing in a speaker by: obtaining a signal having audio content, determining a first value of a spectral density of the audio content at a first resonant frequency, the first resonant frequency associated with mechanical movement of at least one member of the speaker assembly, determining a second value of the spectral density of the audio content at a second resonant frequency, the second resonant frequency associated with a port of the speaker assembly, determining that the signal is to produce a beep of the speaker at the second resonant frequency in response to the first value and the second value, producing a modified signal by limiting the spectral density of the audio content at the first resonant frequency, and providing the modified signal to the speaker.

Description

Dynamic eliminating buzzer of loudspeaker

RELATED APPLICATIONS

This application claims priority from U.S. provisional application No. 62/767,953 filed on 2018, 11, 15, 35 u.s.c.119(e), which is incorporated herein in its entirety.

Technical Field

This description relates generally to improving speaker quality by reducing or suppressing buzzing of a speaker during playback of audio content. More particularly, the present description relates to identifying mechanical and acoustic resonances that lead to the generation and amplification of buzzes and limiting the audio content that causes such resonances.

Background

Modern handheld electronic devices, such as smart phones and tablet computers, require sound playback capabilities that can meet the ever-increasing consumer expectations regarding sound quality. However, significant improvements in the performance of such speakers are quite challenging due to the limitations imposed by the small size of the speaker (which needs to be mounted in a handheld device). In particular, when the volume of the played back audio content is large, the speaker is liable to emit a buzzer. In the frequency range of 5-10kHz, the beeps may have objectionable tones, depending on the size and design of the speaker. The presence of such a beep significantly reduces the user's enjoyment of the audio content and detracts from the user's overall experience. Some causes of the buzzing may originate from the electronic circuit. For example, a beep may be due to stray current caused by a ground loop effect in which the speaker shares the same ground with another device on the same or a different circuit. However, other causes of buzzing may be inherent to the design of the speaker. Thus, eliminating or at least reducing buzzes may require identifying the root cause of the buzzes and addressing in a way that has as little impact on the audio content as possible.

Drawings

Aspects and implementations of the present disclosure will be understood more fully from the detailed description given below and from the accompanying drawings of various aspects and implementations of the disclosure, which, however, should not be taken to limit the disclosure to the specific aspects or implementations, but are presented for purposes of explanation and understanding only.

Fig. 1 depicts a schematic diagram showing a speaker mounted in a side-sounding speaker box, which in turn is located inside a larger device (e.g., a smartphone), and a processing device for implementing buzzing cancellation, according to one embodiment.

Fig. 2a schematically illustrates the origin of a buzzing identified in the present disclosure, wherein the audio content (e.g., music) causes mechanical chatter (tank) resonances, resulting in buzzing harmonics at progressively higher frequencies, according to one implementation.

Fig. 2b schematically shows how both audio content and buzzing harmonics can be amplified by acoustic resonance of the loudspeaker enclosure port according to one implementation.

Fig. 2c schematically shows how limiting the audio content with a static notch filter at or near the tank resonance frequency may suppress the chatter due to tank resonance and reduce buzz harmonics according to one implementation.

Fig. 2d schematically shows how a further improvement may be achieved with a dynamic notch filter that may suppress audio content at or near the tank resonance frequency only as needed to mask buzzes of audio content present near the port resonance frequency, according to one implementation.

Figure 3 illustrates components of a processing device that may be used to implement dynamic buzzing cancellation in a speaker according to one embodiment.

Figure 4 shows one particular implementation of the functional relationship of the components of a processing device that may be used to implement dynamic buzzing cancellation in a loudspeaker.

Figure 5 illustrates steps of a process that may be used to implement dynamic buzz cancellation in a speaker using previously stored calibration data, according to one embodiment.

Figure 6 illustrates steps of a process that may be used to create calibration data for use in the dynamic buzz elimination process of figure 5, according to one embodiment.

Detailed Description

Modern smart phone technology utilizes speakers whose small size makes achieving high quality sound performance quite challenging. In particular, spurious noise (buzzes or audio distortions) may be heard often during playback. Such a beep is the result of a complex interaction of various mechanical resonances present in the speaker assembly. It may be difficult to avoid such resonances due to the relatively small loudspeaker assembly cabinet required to produce a large volume. A typical smartphone speaker design may include a side-firing speaker box with an opening-a port for sound to escape from the box. In some implementations, the speaker is a side-emitting speaker disposed on an adjacent side of the side having the port. The port may be a slot whose length exceeds its width. Such a port may have its own acoustic resonance that may amplify the sound signal as sound escapes through the port. The acoustic port resonance may occur at a frequency: where the wavelength of the sound is comparable to the port size. For example as in modern smart phonesIn common designs, a narrow port of length l ≈ 1in may be expected to resonate at such frequencies: for these frequencies, half the wavelength of the sound fits into the length of the port, i.e., at f_pU/2l, where u 340m/s is the speed of sound. For port length l ≈ 1in, this provides a resonant frequency f for the port_pEstimate of 7 kHz. Since other various designs of speaker box ports are available at different resonant frequencies, it should be understood that this number is by way of example only. For example, in some implementations, the length (or width) of the port may correspond to the full wavelength of sound, one and one-half wavelengths of sound, or any integer multiple of the half-wavelength of sound. In some implementations, the ports may have a non-rectangular shape (e.g., circular) and the port resonance(s) may be determined as a solution to the acoustodynamics of the corresponding hole. For various designs, the port resonance may be anywhere within the 5-10kHz frequency range, even outside of that range. The presence of port resonances may be a technical nuisance in some instances, or a feature that may be advantageous for high frequency tones in other implementations.

Fig. 1 illustrates, by way of example, a possible design 100 of a speaker assembly included in a device 105, such as a smartphone, according to one implementation. The speaker box 110 may include a cavity that houses a speaker 115. The port 120 may connect the cavity of the speaker box 110 with an external space. The design of the port 120 may be such that the port has one or more resonances. The particular design shown in fig. 1 is referred to as a side-firing speaker, but a variety of other designs are possible, such as a front-firing speaker, a bottom-firing speaker, a top-firing speaker, and so forth. In some implementations, the speaker can be a micro-speaker, e.g., a speaker whose sound emitting diaphragm (cone, etc.) has a perimeter (e.g., outer perimeter) of less than 5 inches (or in other implementations, less than 3 inches), e.g., a speaker within a smartphone, tablet, etc.

In the following, for convenience of description and not by way of limitation, it will be assumed that at frequency f_pWhere there is a port resonance. However, the device is not limited to the specific type of the deviceRather, it should be understood that the same inventive concepts and solutions may be applied in the case of multiport resonances.

The port resonance can be measured by its quality factor Q_pTo characterize. Port resonance may amplify sound, such as music or speech, generated by speaker 115 and escaping through port 120 more or less efficiently (depending on the figure of merit). In general, the emitted sound may be contained exactly at the width of the port resonance (full width at half maximum) Δ f_p＝f_p/Q_pInner frequency. Unfortunately, port resonances can not only amplify "good" signals (e.g., music, speech, or any other desired signal) intended for playback, but can also enhance any undesired sound that may be generated within the speaker box 110. For example, the speaker 115 may utilize a mechanical diaphragm or diaphragm (not shown in fig. 1) to produce sound, but the mechanical diaphragm may also generate stray buzzes at low frequencies (e.g., near 1kHz frequencies or any other frequencies), depending on the design of the diaphragm. Buzzes may be generated due to imperfections in the diaphragm or mechanical support of the diaphragm in speaker 115. Since converting an electrical signal into sound waves requires that the diaphragm of the speaker 115 is movable, it is impossible to completely eliminate the buzzing. Additionally, the beeps may not come directly from the diaphragm, but rather are generated by the speaker assembly or any other component or member of the device 105 (e.g., the speaker box 110). For example, buzzes may result from mechanical vibrations 125 of the speaker box 110; for example, from relative movement of various components (e.g., walls) of the speaker box 110. Alternatively, the tremor may be associated with how the speaker box 110 is attached to the device 105. The source of the beeps in the speaker assembly may be numerous, as virtually any mechanical connection may be subject to at least some amount of chatter. Port resonance can amplify even small buzzes/chatter and adversely affect the user experience.

Fig. 1 shows how the basis of the inventive solution can be implemented in one possible embodiment. A signal (shown with an arrow) may be obtained from the radio antenna 107. In one implementation, the signal may have audio content that may be encoded as a low frequency modulation of a high frequency electromagnetic signal received by the antenna. Alternatively, the signal may be read from the memory 108 or obtained over a network connection or Wi-Fi connection (not explicitly shown). In one implementation, the memory 108 may be a cloud storage. The signal may be provided to a processing device 101 where the signal may be amplified, equalized, and filtered to modify the spectral content of the signal in the processing device 101. The spectral content may be modified in such a way (see discussion below): buzzes caused by mechanical flutter 125 that is subsequently amplified by port 120 are minimized. The processing device 101 may be purely analog or purely digital, or a combination of analog and digital components. After modifying the signal, the processing device 101 may provide the modified signal to the speaker 115.

Fig. 2a shows one possibility of how buzzing/chattering may affect sound quality according to one implementation. The upper curve shows a possible dependence of the amplitude of the music signal 205 on the frequency. Playback may refer to any music, voice, speech, or any other signal audible to the human ear, and the term "music" is intended to include all such possible meanings. The horizontal axis indicates the frequency of the sound, and the vertical axis shows the Sound Pressure Level (SPL) of the music signal generated by the speaker 115. The dependence of the SPL on frequency can be understood as the spectral (e.g. fourier) expansion of the signal over frequency, wherein the value of the SPL indicates the intensity of a particular frequency represented in the overall sound signal. The spectral distribution of fig. 2a (and subsequently fig. 2b-2d) may be understood as a continuous expansion over frequency (e.g., fourier integration), or alternatively as an expansion over a discrete set of frequencies (e.g., a fourier series), with the degree of frequency resolution depending on the particular embodiment. Frequency may be indicated in Hz; SPL may be indicated in decibels (dB) or some other unit. The plot of SPL versus frequency shown in fig. 2a (and subsequent fig. 2b-2d) should be understood only as a qualitative illustration, and not as specific data measured for any particular loudspeaker device. The music signal 205 may have a wide band of high amplitude in frequencies corresponding to the range of human hearing and may decrease away from this range at low or high frequencies or both.

The music signal 205 may be caused by electromagnetically induced mechanical motion of a moving component (e.g., a diaphragm or diaphragm) of the speaker 115. The motion of the mobile component may further cause additional motion in the speaker assembly, e.g., other portions of the speaker 115 and/or the speaker box 110 surrounding the speaker 115, and/or connection(s) of the speaker box 110 to an external environment (e.g., a circuit board, a device housing, etc. of a device such as the device 105 housing the speaker 115). Alternatively, mechanical motion in the speaker 115, the speaker box 110, or other portion of the device 105 may be caused by modulation of air pressure caused by the music signal 205 around the speaker 115, inside or outside the speaker box 110 or device 105. The mechanical movement (mechanical vibration 125) may be at a certain tank frequency f_bHas a resonance associated with it (the terms "cabinet" and subscript indicate the relationship of the resonance to certain parts of the speaker assembly (e.g., the cabinet)). The frequency of such flutter/tank resonance may be about 1 kHz. However, depending on the specific embodiment of the loudspeaker 115 and/or the loudspeaker cabinet 110 (e.g. the dimensions of its components), the frequency f of the buzzer resonance is_bMay differ significantly from 1kHz, e.g. f_bIt may be anywhere within or even outside the range of 100 Hz-1.5 kHz. The frequency at which the tank(s) resonate may depend on the dimensions and elastic properties of the loudspeaker assembly components and the manner in which these components are connected to each other. Additionally, multiple dither/tank resonances may exist within a given system and affect each other in a complex manner. Since the music signal 205 can be extended to the tank resonance f_bSo it can-with varying degrees of efficiency-depend on the frequency f of the resonance_bAnd its quality factor Q_bThe quality factor Q of_bThe extent to which the resonances couple with the environment is described-at least one such resonance is induced (see figure 2a for the flutter/tank resonance 210). The non-linearity (non-harmonicity) present in any realistic mechanical vibration system will not only cause at f_bAnd may also cause a magnetic resonance having a different (e.g.,higher) additional buzzer harmonics of the frequency.

The lower curve shows in qualitative terms the sound pressure level of the buzzing harmonic 215, which buzzing harmonic 215 is caused by the music signal 205 passing through the tank resonance 210 and extends to other frequencies/harmonics due to the dissonance in the oscillation of the source(s) of mechanical vibration. The relative sizes of SPLs of the music signal 205 and the buzzer harmonic 215 are presented for illustrative purposes only and may be very different in speakers having different designs, sizes, etc. and operating under different conditions. The diagram of fig. 2a shows the maximum value of the buzzer harmonic, which lies at about the main buzzer frequency f_bMultiple of (in particular 2 f)_b、3f_b、4f_bEtc.). However, in a specific implementation, the distribution of the buzzing harmonics may be different from that shown in fig. 2 a. For example, the buzzing harmonics may come from multiple major frequencies f corresponding to different mechanical vibrations_bFor example, the vibration of a speaker diaphragm/diaphragm, the vibration of a speaker 115 within a speaker box 110, the vibration of a speaker box 110 within a device (e.g., a phone) 105, etc. As shown graphically in FIG. 2b, the buzzing harmonic 215 may extend to the frequency(s) f of the port resonance 220_pAnd is measured by the frequency f_pAnd (5) amplifying. Fig. 2b shows how the SPL of both music signals and beeps can be amplified by port resonance, according to one implementation. Music signal 225 may be at f_pAt or in f_pWith a near amplification maximum. Likewise, the buzzer harmonic 235 may be at f_pAt or in f_pThe vicinity becomes resonantly enhanced. Fig. 2b is intended to highlight the basic feature of sound amplification by port resonance. In a particular embodiment, the magnitude of the signal enhancement may be different from that in fig. 2b, which should not be understood to refer to measurements of any particular system. The vertical scale in fig. 2b and fig. 2a may be very different. In particular, fig. 2a may refer to an assumed case where there is no port resonance, e.g. the speaker 115 emits sound waves directly into the external space instead of the speaker box 110, or another case where there is a port resonance but it is outside the frequency range of human hearing. SPL on FIG. 2b, on the other hand, may refer toInstead of the actual sound pressure level existing outside the speaker box of the speaker embodiment, the port resonance 220 actually amplifies the emitted sound. The presence of the port resonance 220 may be a design feature intended to improve the acoustic output and overall performance of the speaker. Thus, amplification of the music signal 225 may be desirable. Unfortunately, port resonance 220 may non-selectively amplify a signal that is present inside speaker box 110 and has a frequency at or near f_pIncluding the undesired spurious beep harmonics shown in figure 2 b. From the perspective of the user of the speaker, the buzzing amplified by the port resonance can significantly affect the performance of the speaker and significantly reduce the user's enjoyment of the sound playback. However, it may not be feasible to eliminate the buzzing harmonics with the prior art. For example, a conventional equalizer may be ineffective because it may modify a signal just before it is provided to the speaker, while a beep originates inside the speaker/speaker box after equalization.

To solve at the port resonance frequency f_pBeeps (i.e., eliminating the beep harmonics 235 as much as possible without adversely suppressing the music signal 225), by at the point of origin of the beeps, at the frequency f_bAt or in f_bIt may be more efficient to suppress buzzes in the vicinity to reduce buzzes. In particular, the main dither/tank resonance may be at a lower frequency f_bWhere it occurs and extends to higher frequencies, e.g. f in the form of a buzzing harmonic 235_p. Because the pair has a frequency f_bWill also reduce the buzzer harmonic 235, so first the amplitude of the main buzzer oscillation at f is suppressed_bIt may be advantageous to suppress mechanical vibrations. In one embodiment, the frequency of the higher harmonics may be the main frequency f_bInteger frequency of (e.g. 2 f)_b、3f_b、4f_bAnd so on. By way of example and not limitation, the tank resonance may be at f_bAt 1kHz, the port resonance can be at f_p7 kHz. It may also be noted that the buzz harmonics 235 occur in response to the music signal 225, thus reducing the music signal 225 may at least partially cancel the buzz harmonics 235.

With this understanding, FIG. 2c illustrates that, according to one implementation, the port frequency f is not affected_pHow the size of the music signal at the same frequency f can be reduced_pThe buzzer sound of (c). For example, the music signal may be filtered by a notch filter 231, and the center frequency of the notch filter 231 may be at the buzzer resonance frequency f_bAt or in f_bNearby. A notch filter (band reject filter ) is a filter that passes most frequencies unchanged but attenuates/eliminates frequencies within a certain range. The width of the rejection band of the notch filter 231 may vary depending on the specifics of the buzzer resonance. In some embodiments, the width of the rejection band may be hundreds of Hz or greater. In some embodiments, the width of the rejection band may be one semitone or less. In other embodiments, the full width Δ f of the tank resonance 210 may be considered_b＝f_b/Q_bThe width of the rejection band is chosen and may be wider than, about the same as, near half of, or much smaller than a full width. For example, the full width Δ f of the buzzer resonance may be set_bDividing into N frequency intervals delta f-delta f_bN and the notch filter is configured to suppress any number of such intervals. In some embodiments, only one interval δ f may be suppressed. In other embodiments, several intervals may be suppressed as desired, including N intervals (one full width of the resonance) or more than N intervals.

The notch filter 231 may modify the music signal 225 at or near the buzz resonance 210 such that the filtered music signal 245 is for a near f_bThe frequency of (1) causes SPL to switch out. The music signal 245 may suppress frequency components within the suppression band to a desired degree depending on the settings or parameters of the notch filter. For example, in some embodiments, these frequency components may be only slightly suppressed, but in other embodiments, these frequency components may be almost completely eliminated. Accordingly, at f, compared to the music signal 225 before filtering is performed_bAt or in f_bNearby with lower spectral densityWill result in a trembling/bin frequency f_bAt or in f_bThe nearby mechanical buzzing/chattering is reduced (in some instances significantly reduced). The reduced magnitude of the primary buzzing resonance may result in a higher frequency (e.g., 2 f)_b、3f_b、4f_bEtc.) is significantly reduced, as shown qualitatively in fig. 2 c. Despite resonance f at the port_pAt or in f_pNearby harmonics may still be amplified by port resonance, but this amplification may not be as significant as the case of the buzzing harmonic 235 generated by the music signal 225 without filtering. Thus, the buzzing SPL can be reduced to a significant degree, and in some instances can be reduced below a level that can be detected by a user.

However, the speaker is at the port frequency f_pThis improved performance in the vicinity may be near the tank resonant frequency f_bIs accompanied by a disadvantage at a low frequency, close to the tank resonance frequency f_bAt low frequencies, the music signal 245 may now be mostly missing. The missing portion of the spectrum may correspond to a key tone of music playback. For example, frequency f_b1kHz is close to high C (treble C) tones. Eliminating such tones altogether may adversely affect the user's enjoyment of the playback.

However, in some cases, f is eliminated completely_bNearby frequencies may not even be necessary. For example, if the spectral content of the music signal 245 is sufficiently strong, the subjective perception of the user at the frequency f may be masked_pAt or in f_pIntensity of nearby beeps. "spectral content" may refer to the SPL associated with a particular frequency (or interval of frequencies) of the music signal 245, e.g., a fourier harmonic of the music signal 245. For example, the sound energy (masking energy) of the music content output by the speaker may exceed the sound energy of the beep. In this case, the user may not be able to detect the presence of the buzzing harmonic 235 on top of a sufficiently strong playback signal. In this case, the notch filter is used at ≈ f_pMay be negligible and, in fact, the benefit is given by the music signal at ≈ f_bOver distortion at lower frequencies. This indicates that while an always-on notch filter (static notch filter) is beneficial in some cases, in other cases such continuous filtering may not be necessary.

In some embodiments, dynamic notch filters (adaptive notch filters), i.e., filters that are selectively turned on and off depending on the instantaneous spectral content of the music signal, may provide excellent performance and a better overall user experience. For example, the spectrum analyzer may perform an analysis of the music content input to the speaker and determine the port resonance f_pWhether the nearby music content is strong enough to mask the buzz harmonic 255 generated by the speaker/speaker box and amplified by the port resonance 220. Indicating port resonance f at spectrum analyzer data_pIn those instances where nearby music content is insufficient to mask a beep, the notch filter may be turned on. In contrast, at the spectrum analyzer data indicative port resonance f_pThe notch filter may not be enabled in those instances where the nearby musical content is strong enough to ensure that the user is unlikely to discern the buzzing harmonic 255.

In some embodiments, depending on the musical content, the dynamic filter may always be in one of two states: (1) a fully open state, and (2) a fully closed state. In the off-state, no band rejection will occur, while in the on-state, the notch filter will be fully enabled. The music signal may be continuously monitored and the controller may perform a "notch filter on/off decision" as to which of the two states of the dynamic filter is to be selected depending on the instantaneous spectral density of the sound content. The controller may be a software component executed by a processing device of the device 105. Alternatively, the controller may be implemented as a separate hardware component or a combination of hardware and software components.

In some embodiments, the spectral analysis of the music signal may be performed discontinuously. Instead, the spectrum analyzer may collect spectrum data at the beginning of a discrete predetermined time interval, and the controller may not perform an on/off decision until the end of the current time interval. The time length of such intervals may vary from a fraction of a second to at least a few musical tones or even longer. The length of the time interval may be a function of how fast the spectral content of the music signal changes over time. For example, the spectral analysis may initially be arranged to be performed after each time interval τ, where τ may represent some predetermined optimal time interval. The time interval between two successive analyses can be shortened if the spectrum analyzer detects that the spectral content of the music signal changes significantly over time τ. Conversely, if the spectrum analyzer detects that the spectral content of the music signal does not vary significantly over time τ, the interval between two successive analyses may be extended.

In some embodiments, the strength of the notch filter may vary depending on the result of the spectral analysis of the music signal, as shown in fig. 2 d. For example, when the spectral content of music signal 265 is at f_pAt or in f_pWhere the vicinity is rather large, but still insufficient to mask the buzz harmonic 275, the dynamic notch filter may be set to filter out only at f_bAt or in f_b20%, 40%, 60%, etc. or any other desired portion of the nearby music signal, depending on f_pAt or in f_pSpectral density of both nearby music signal 265 and buzzing harmonic 275 (e.g., both at f_pAt or in f_pRelative intensity of the vicinity). To modify the music signal 265 only when necessary, the strength of the dynamic notch filter can be set by the controller to be only sufficient to mask the beep harmonic 275, which means that the masking energy of the audio content masks the acoustic energy of the beep. As in the embodiments described above, the spectrum analyzer may perform the analysis of the music signal continuously or at discrete time intervals, the analysis being repeated more frequently when it is detected that the music signal changes significantly over time, and less frequently when it is detected that the music signal changes more gradually.

In some embodiments, instead of changing the strength of the dynamic filter, the width of the dynamic filter may be changed depending on the result of the spectral analysis of the music signal, as shown in fig. 2 d. For example, depending on the music signal 265 at f_pAt or in f_pThe dynamic notch filter can be set to the full width Δ f for dither/tank resonance for nearby spectral content_bHalf-width, quarter-width or at f_bAt or in f_bAny one or more ranges of nearby frequencies are filtered. As in the case of a dynamic notch filter with varying strength, the width of the dynamic notch filter may be set by the controller to be only sufficient to mask the buzz harmonic 275 in order to suppress the music signal 265 only when necessary. In some embodiments, both the strength and width of the dynamic notch filter may be responsive to the signal at f_pAt or in f_pThe spectral density of both the nearby music signal 265 and the buzzing harmonic 275 varies.

Fig. 3 shows an exemplary embodiment of the processing device 301 of fig. 1 implementing the above described elimination buzzer algorithm. The processing device 301 may be capable of processing the electrical signal and providing the audio content of the electrical signal to the speaker 315 to convert the audio content into sound 350. The electrical signal may represent music, speech, voice, a film sound, a sound of a living body, a natural sound, or any other type of audio signal. The electrical signal may be amplitude modulated, frequency modulated or phase modulated. The modulation of the electrical signal may correspond to the audio content carried by the signal. The electrical signals may be obtained through an interface 302, which may be connected to a radio, Wi-Fi, or any other type of electromagnetic antenna or network adapter. The signal source may be a memory 108, which memory 108 may include external memory (e.g., as a storage device provided by a cloud service), as shown in fig. 1 for some embodiments. In other implementations, the signal may be derived from a memory 325, which memory 325 may also store audio content intended for playback. In such implementations, the electrical signal may be generated upon a memory read operation performed by the CPU 320. The electrical signals may be analog or digital. The electrical signal may be processed by amplifier 305 and equalizer 310 to modify the amplitude and spectral properties of the audio content of the electrical signal before being provided to dynamic notch filter 330 and subsequently to speaker 315. Additionally, the spectrum analyzer 340 may access the tones of the electrical signalThe frequency content. The spectrum analyzer 340 may analyze the amplitude and spectral distribution of the audio content. The spectrum analyzer 340 may evaluate the entire frequency range of the audio content, or in some embodiments, the spectrum analyzer 340 may only evaluate the tank resonance frequency f_bAnd port resonance frequency f_pIs analyzed in the vicinity of (a). The vicinity of the aforementioned frequency may refer to the portion corresponding to the full width, half-width or any other requirement of the full width of the resonance; nearby may also refer to a frequency interval that is wider than full width. The CPU 320 of the processing device 301 may retrieve the calibration data from the memory 325 and provide the calibration data to the controller 335. The controller 335 may determine whether the audio content input on the speaker 315 is likely to be at the frequency f of the port resonance_pAt or in f_pThe proximity causes an output beep of the speaker 315 (or the speaker box 110/mechanical connection of the speaker box to the device 105). For example, the calibration data may include a threshold level of spectral density of the audio content at which the tank resonance frequency is sufficient at the port resonance frequency f_pA buzzer of the loudspeaker is generated. In some embodiments, the controller 335, in conjunction with the spectrum analyzer 340 and/or the CPU 320, may then determine an optimal setting or parameter of the dynamic notch filter 330 that will reduce the magnitude of the beep generated after the speaker 315 converts the input audio content into sound 350 output by the speaker without unnecessary distortion of the audio content. In one implementation, the settings or parameters of the dynamic notch filter 330 may be fixed. In other implementations, the settings or parameters of the dynamic notch filter 330 may be adjustable. For example, the controller 335 may be tuned to the frequency f at which the tank resonates_bAt or in f_bThe spectral density of nearby audio content output by amplifier 305 and/or the spectral density of audio content output by equalizer 310 are compared and compared to the port resonant frequency f_pAt or in f_pThe spectral densities of nearby audio content are compared. The controller 335 may retrieve calibration data that may comprise a table (or mathematical formula, or any other type of correspondence) derived from the resonance frequency f at the tank_bAt or in f_bValue index of nearby spectral contentAnd is shown at the port resonant frequency f_pAt or in f_pA minimum (threshold) value of nearby spectral content that is sufficient to mask the buzzer harmonics caused by the tank resonance when driven by the audio content of the signal input to the speaker 315.

If at the port resonant frequency f_pAt or in f_pThe nearby spectral content is above the minimum in the calibration table, then the controller 335 may not activate the dynamic notch filter 330 at all. However, if at the port resonant frequency f_pAt or in f_pThe nearby spectral content is below the minimum required for masking, the controller 335 may further process the calibration data to retrieve the optimal settings or parameters of the dynamic notch filter 330, such as the strength and/or width of the filter. In some embodiments, the optimal settings or parameters for the dynamic notch filter may be retrieved from a calibration table. In other embodiments, the optimal values of the strength and/or width of the dynamic notch filter 330 may be encoded in the calibration data in the form of mathematical expressions. The controller 335 may provide the retrieved settings to the dynamic notch filter 330. The processing device 301 may then send the modified audio signal with the audio content to the speaker 315 through the dynamic notch filter 330. In some implementations, if the parameters of the dynamic notch filter are fixed, sending a signal through the dynamic notch filter may be equivalent to sending a signal through the static notch filter.

After the predetermined time τ has elapsed, the controller 335 may activate the spectrum analyzer 340 to repeat the spectrum analysis of the audio content again. In one implementation, the time τ may be set in the memory 325. The controller 335 may provide the new optimal settings to the dynamic notch filter 330 to account for changes in the spectral density of the audio content over time τ. The controller may store spectral density data for at least two (e.g., consecutive) analyses and determine when the next analysis should be performed. For example, as explained above, if the spectral density of the audio content remains relatively constant over multiple analyses, the controller 335 may schedule the next analysis to occur after a time greater than the set time interval τ that has elapsed. Conversely, if the spectral density of the audio content changes significantly between subsequent analyses, the controller 335 may schedule the next analysis to occur after a time interval that is less than the set time interval τ that has elapsed.

Various implementations of the processing device 301 shown by way of illustration in fig. 3 may be appreciated. For example, some of the components included in FIG. 3 may not be present in some embodiments. For example, amplifier 305 or equalizer 310 may not be present, or alternatively may be located external to processing device 301. The processing device 301 may have multiple CPU 320 and/or memory 325 devices. The controller 335 may have its own CPU and/or memory (e.g., cache) or may utilize the capabilities of the CPU 320 and/or memory 325 of the processing device 301. The processing device 301 may be a smart phone, a flip phone, an iPad, an iPod, a laptop or any other computer or communication device with audio speakers.

The processing device 301 may be a system on a chip (SoC) that integrates all or most of the components on the same integrated circuit. Alternatively, some or all of the components shown in fig. 3 may be assembled using a motherboard-type architecture, with different devices/components attached to a central motherboard. In some embodiments, the speaker 315 may be external to the processing device 301. In other embodiments, the speaker 315 may be part of the processing device 301, as indicated by the dashed rectangle in fig. 3. Some of the components of the processing device 301 may be combined. For example, amplifier 305 and equalizer 310 may be combined. In some implementations, the controller 335 and/or the spectrum analyzer 340 may be integrated into the dynamic notch filter 330. Some of the components shown in fig. 3 may be analog, while other components may be digital. In some embodiments, all components of the processing device 301 may be digital. Some of the components shown in fig. 3 (e.g., the controller 335 and the spectrum analyzer 340) may be purely software implemented.

In the embodiments discussed above, the spectrum analyzer 340 analyzes the audio content before it is input to the speaker 315. This may make it necessary to map (calibrate) the (known) electrical signal input at the loudspeaker 315 to the (predicted) sound output (SPL) of the loudspeaker 315. Such calibration may be performed during manufacturing and is discussed in more detail below. In other embodiments, the spectrum analyzer 340 may receive the actual SPL data output by the speaker 315 via a special hardware device, such as a feedback microphone mounted near a port of the speaker box. In such embodiments, only a reduced amount of calibration may be required. However, in those instances where additional hardware may not be practical, careful calibration of the speaker input output may significantly improve the user experience.

Figure 4 shows one possible functional relationship 400 between the different components of the elimination buzzer previously shown in figure 3. By way of example and not limitation, electrical signal 401 received by an antenna or network adapter may be processed by amplifier 405 and equalizer 410 and input to spectrum analyzer 440 before being delivered to dynamic notch filter 430. Dynamic notch filter 430 may include a static notch filter 431, a bandpass filter 433 connected in parallel with static notch filter 431, and a controller 435 connected in series with bandpass filter 433. In the implementation shown in fig. 4, the static notch filter may receive a first copy of the audio signal and the band pass filter may receive a second copy of the audio signal. The first copy and the second copy may be identical. The static notch filter may be configured to completely cancel (or almost completely cancel) at the frequency f of the tank resonance_pAt or in f_pAll input frequencies within a given frequency interval δ f in the vicinity. The band pass filter may be configured to pass only input frequencies within the same frequency interval δ f. Thus, when the signal input to dynamic notch filter 430 has a frequency outside of interval δ f, bandpass filter 433 will completely shut off the lower path for the input signal regardless of the state of controller 435. Meanwhile, the input signal reaches the speaker 415 without hindrance through an upper path including a static notch filter 431, and the static notch filter 431 does not affect frequencies other than the interval δ f. On the other hand, when inputting lettersThe static notch filter 431 may close the upper path when the signal is just within the interval δ f. So in order to reach the speaker 415, the signal must follow the lower path. Because the band pass filter 433 is completely (or almost completely) transparent to the signal within δ f, the portion of the input signal that reaches the speaker 415 can be determined by the controller 435. In the simplest implementation, the controller 435 may be a circuit element (e.g., a variable resistor, capacitor, or inductor, or a combination thereof) having a variable impedance. In some embodiments, it may be advantageous to configure the controller 435 so that the reactive portion of the impedance is close to zero so as not to change the phase of the input signal.

The controller 435 may be in communication with the spectrum analyzer 440, as explained above with respect to fig. 3. The controller 435 may obtain data from the spectrum analyzer 440 (continuously or at predetermined times). In the simplest case, the controller 435 may receive information about the frequency at two frequencies (the frequency f of the tank resonance)_bFrequency f of port resonance_p) Information of the audio content of the input signal. The controller 435 may then retrieve the calibration data from the system memory 325, as explained above with respect to fig. 3, and determine an optimal value for the variable impedance of the controller 435 to be at the frequency f of the tank resonance_bAt or in f_bNearby input signals are limited to frequencies f that will resonate at the port_pAt or in f_pThe nearby buzzing harmonic (caused by such an input signal) is reduced to the extent necessary to just below the threshold of the user's hearing, which is at the frequency f of the tank resonance_bFrequency f of port resonance_pAs a function of the expected audio content. Fig. 4 shows only one possible exemplary implementation of a dynamic notch filter based canceling buzzer, but many other implementations may also cut out the audio content at low frequencies by using the general inventive concept explained above to limit the buzzer harmonics at high frequencies. For example, the controller 435 may contain a limiter with adjustable parameters. The controller 435 may have analog components or may be purely digital. In some embodiments, the controller 435 may be implemented as a separate hardware component. However, in other implementations, the controller 435 may beSoftware implemented by the CPU 320 based on instructions retrieved from the memory 325 without any additional hardware components. In some embodiments, the signal filtered by static notch filter 431 and the signal sent through bandpass filter 433 and controller 435 may be added in an adder (not explicitly shown in fig. 4) before providing the modified audio signal to speaker 415.

Fig. 5 shows possible steps of a process 500 for preventing amplified buzzes in a speaker that can be implemented with the system shown in fig. 3-4. In some embodiments, process 500 may be performed without reference to any particular components shown in fig. 3-4. At step 510, a signal (e.g., an electrical signal) may be obtained by radio, Wi-Fi, or any other type of electromagnetic reception or over a network, or generated when a read operation from memory is performed. The signal may be analog or digital. The signal may have audio content, such as music, speech, voice, movie soundtrack, or any other type of audio signal. For example, the signal may be a high (radio) frequency carrier modulated to have low frequency audio content. In some implementations, the audio content may be encoded in pure digital form and does not utilize any high frequency carrier. The audio content may be intended to be converted into sound waves by a loudspeaker. The signal may be amplified, filtered, processed in some other way so that the audio content of the signal may be modified before being provided to the speakers.

At step 520, the spectral density of the audio content of the signal may be analyzed. For example, it may be determined that at a first frequency f_bAt or in f_bSpectral density of nearby audio content, the first frequency f_bAssociated with the mechanical resonance of the loudspeaker. Mechanical resonance may refer to any mechanical motion (vibration) of any component of the speaker, such as a diaphragm (diaphragm), or of any component of the speaker assembly (e.g., on the side of the speaker housing), or of the speaker/speaker assembly relative to the environment (e.g., the body of a phone or any other electronic device). The term may be at or near the frequency of the mechanical resonanceRefers to the full width, half-width or any other desired portion of the full width of resonance; the term "at … … or near … …" may also refer to a frequency interval that is wider than full width.

At step 530, it may similarly be determined that at the second frequency f_pAt or in f_pSpectral density of nearby audio content, second frequency f_pAssociated with the acoustic port resonance of the opening (port) of the speaker. Spectral density can be extracted using spectral (fourier) analysis of the audio content. The spectral analysis may be performed using hardware components or a combination of hardware components and software resources, or may be performed using only software. Frequency f of the first mechanical vibrational resonance_bFrequency f of resonance with the second acoustic port_pMay be previously known (e.g., via a calibration process performed during manufacturing).

At step 540, speaker calibration data may be retrieved. The calibration data may be stored in a memory device, which may be local to the device hosting the speakers. In some embodiments, the calibration data may be stored remotely using a cloud service accessible via a network. The calibration data may represent the results of multiple measurements performed on the same speaker or other speakers of the same type. In some embodiments, at step 550-. For example, at step 550, the calibration data may be used to estimate the port resonance frequency f to be used by the speaker_pAt or in f_pSPL of audio content of a nearby generated instant signal. Similarly, at step 560, the calibration data may be used to estimate the frequency f at the port_pAt or in f_pSPL of nearby buzzing harmonics that would be caused in a loudspeaker enclosure if an unmodified signal were provided to the loudspeaker. At step 565, an evaluation may be performed to determine whether the existing audio content is strong enough to be masked at f_pBuzzing/chattering. If the calibration data so indicates, step 570 may be performed and may not be repeatedThe instant signal is provided to the speaker with any modification to the audio content of the instant signal. For example, at step 570, the dynamic notch filter may be bypassed or not enabled (e.g., the filter may remain in an "off state).

In contrast, when the calibration data indicates a resonant frequency f at the port_pAt or in f_pThe spectral density of nearby audio content is too weak to mask at the tank resonance frequency f_bAt or in f_bUpon buzzing/dithering caused by the spectral density of nearby audio content, a decision may be made at step 565 to initiate a dynamic notch filter. The dynamic notch filter may then be at the tank resonance frequency f_bAt or in f_bNearby audio content is limited enough to ensure at the port resonant frequency f_pTo the extent that the humming harmonics are not discernable by the user from the background of the audio playback. Thus, at step 580, the processing device may retrieve from the calibration data the dynamic notch filter given at the tank resonant frequency f_bAnd port resonance frequency f_pAt or in f_bAnd f_pThe settings or parameters needed to mask a buzz of the instant signal in the case of spectral density of the audio content of the nearby instant signal. At step 590, the signal may be provided to the speaker through a dynamic notch filter configured with adjustable settings or parameters obtained from calibration data according to the masking energy present near the frequency of the port resonance.

In some embodiments, the optimal settings or parameters of the dynamic notch filter may be minimal, just enough to mask buzzes but still leave f_bThe audio-in-tolerance of (a) is made as small as possible. In other embodiments, more aggressive restrictions may be implemented to reduce the likelihood that subsequent changes to the audio content will cause the restrictions to be inadequate. The process 500 may be repeated after a predetermined time τ, with new optimal settings or parameters for the dynamic notch filter being re-determined in view of changes in the spectral density of the audio content that have occurred over time τ. The spectral density data of the

multiple steps

520 and 530 of the continuous spectral analysis may be stored in memory andand is used to determine when the next analysis should be performed. For example, if the spectral density of the audio content remains relatively constant over multiple analyses, repetitions of process 500 may be scheduled after a time greater than the time τ that has elapsed. Conversely, if the spectral density of the audio content has changed significantly over the last multiple analyses, the next execution of the process 500 may be set to occur earlier than after the time interval τ has elapsed.

FIG. 6 illustrates one possible embodiment of a calibration process 600 that may be performed during manufacturing. For example, such a calibration process may be performed after the speaker is manufactured and assembled into a device (e.g., a phone), but before the hardware and/or software of the dynamic notch filter is installed into the device. The calibration process 600 may be performed after the physical components of the speaker, speaker box/assembly are put in place. At step 610, a first frequency f associated with a mechanical (cabinet) resonance of a speaker/speaker assembly may be identified_b. For example, a loudspeaker may be affected by a harmonic single frequency electrical signal and its electromagnetic impedance measured from the frequency of the harmonic signal. Alternatively, the sound pressure level produced by the loudspeaker in response to such harmonic electrical signals may be measured instead. Depending on the geometry/size of the loudspeaker/loudspeaker assembly, at relatively low frequencies f_bSuch tank resonances are identified at 0.1-1.5KHz, although lower or higher frequencies f may also be achieved_b. At step 620, a second frequency f associated with an acoustic (port) resonance of the speaker box opening may be identified_p. Depending on the geometry of the port and speaker/speaker assembly, the port resonance f can be identified at higher frequencies, substantially on the order of a few KHz_pAlthough a higher frequency f, e.g. on the order of 10KHz or even higher for a smaller port, may also be identified_p。

At step 630, a test/calibration signal may be prepared. The calibration signal may have an audio content with a frequency f at the tank resonance_bFrequency f of port resonance_pAt or in f_bAnd f_pA desired spectral density in the vicinity. In a simple implementationIn an example, only two spectral densities may be identified, and non-resonant frequencies may be ignored. In more complex calibration processes, the spectral density at more than two frequencies can be controlled. In some embodiments, the audio input of the calibration signal may be controlled for multiple (or even quasi-continuous) control frequencies. In the following, for simplicity, two parameters (at f) are described_bAnd f_pSpectral density of (b) but the multi-parameter calibration process should be considered as a straightforward generalization.

At step 640, the calibration signal is provided to the speaker. At step 650, it is determined that f is_pWhether the spectral density of the audio content is sufficient to mask the spectral density of the audio content by f_bBuzzing harmonics caused by the audio content of (a). If the mask is detected to be sufficient, it can be recorded in the calibration data without requiring further dynamic or static cut-outs. In some instances, detection may be facilitated by a human operator directly hearing a beep. In other examples, the detection may be performed solely by software or hardware or a combination thereof that simulates human hearing. If insufficient masking is determined to have occurred at step 650, the settings or parameters (e.g., strength, width, etc.) of the dynamic notch filter may be adjusted at step 660 and may be limited to f_bUntil the spectral density of the audio content at f can no longer be discerned_pUntil buzzing. Once satisfactory masking has been achieved, the settings or parameters of the dynamic notch filter may be used as calibration data along with the data at the control frequency (e.g., f)_bAnd f_p) The spectral densities of (b) are stored together in a memory. The calibration data can be stored at the frequency f resonated by the mechanical box_bIn a table of spectral density indices. Alternatively, the calibration data may be stored at a frequency f that is resonated by the acoustic port_pIn a table of spectral density indices.

If it is determined that the calibration process is incomplete, a decision to continue with calibration may be made at step 675. At step 680, a new signal may be generated that, in the simplest embodiment, is different from the last signal (or from all previous signals)At a control frequency (e.g. f)_bAnd f_p) A magnitude of at least one of the spectral densities of (a).

Steps

640, 650, 660 and 670 may then be repeated. In some embodiments, there may be n ≧ 2 control frequencies, and for each frequency, m different spectral densities (e.g., increasing linearly or logarithmically) may be prepared for a total of n to be used within the course of the calibration process^mA different calibration signal.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other implementation examples will be apparent to those of skill in the art upon reading and understanding the above description. While the present disclosure describes specific examples, it will be appreciated that the systems and methods of the present disclosure are not limited to the examples described herein, but may be practiced with modification within the scope of the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

The implementation of the methods, hardware, software, firmware or code set forth above may be implemented via instructions or code stored on a machine-accessible, machine-readable, computer-accessible, or computer-readable medium which are executable by a processing element. "memory" includes any mechanism that provides (i.e., stores and/or transmits) information in a form readable by a machine, such as a computer or electronic system. For example, "memory" includes Random Access Memory (RAM), e.g., static RAM (sram) or dynamic RAM (dram); a ROM; a magnetic or optical storage medium; a flash memory device; an electrical storage device; an optical storage device; acoustic storage devices, and any type of tangible machine-readable medium suitable for storing or transmitting electronic instructions or information in a form readable by a machine (e.g., a computer).

Reference throughout this specification to "one implementation" or "an implementation" means that a particular feature, structure, or characteristic described in connection with the implementation is included in at least one implementation of the present disclosure. Thus, the appearances of the phrases "in one implementation" or "in an implementation" in various places throughout this specification are not necessarily all referring to the same implementation. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations.

In the foregoing specification, a detailed description has been given with reference to specific exemplary implementations. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. Moreover, the foregoing use of implementations, embodiments, and/or other exemplary language does not necessarily refer to the same implementations or the same examples, but may refer to different and distinct implementations, as well as potentially the same implementations.

The word "example" or "exemplary" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" or "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word "example" or "exemplary" is intended to present concepts in a concrete fashion. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified, or clear from context, "X comprises a or B" is intended to mean any of the natural inclusive permutations. That is, if X comprises A; x comprises B; or X includes both a and B, then "X includes a or B" is satisfied under any of the foregoing examples. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form. Furthermore, the use of the terms "embodiment" or "one embodiment" or "an implementation" throughout this document is not intended to denote the same embodiment or implementation unless so described. In addition, as used herein, the terms "first," "second," "third," "fourth," etc. denote labels as distinguishing between different elements, and do not necessarily have an ordinal meaning according to their numerical designation.

Claims

1. An apparatus for audio signal processing, comprising:

a speaker enclosed in a speaker assembly, the speaker assembly having a port;

a processing device coupled to the speaker, wherein the processing device is configured to execute a dynamic algorithm to attenuate audio distortion of an audio signal amplified by a port resonance of the port, the dynamic algorithm to:

receiving the audio signal, the audio signal having audio content;

determining a first value representative of a spectral density of the audio content at a first resonant frequency, wherein the first resonant frequency is associated with mechanical motion of: (i) a speaker diaphragm; or (ii) a mechanical support for the loudspeaker diaphragm, wherein the first resonant frequency is lower than a second resonant frequency, wherein the second resonant frequency is associated with a port resonance of the port;

attenuating the audio distortion by limiting a spectral density of the audio content at the first resonant frequency to produce a modified audio signal; and outputting the modified audio signal to the speaker.

2. The apparatus of claim 1, wherein to attenuate the audio distortion, the dynamic algorithm applies a static notch filter at the first resonant frequency, wherein the static notch filter has fixed parameters.

3. The apparatus of claim 1, wherein to attenuate the audio distortion, the dynamic algorithm applies a dynamic notch filter at the first resonance frequency, wherein the dynamic notch filter has adjustable parameters, wherein the adjustable parameters are set according to masking energy present near the second resonance frequency of a port resonance of the port.

4. The apparatus of claim 1, wherein the speaker assembly is a side-firing speaker box, the port being on one side of the side-firing speaker box, the speaker being a side-firing speaker disposed on a side adjacent to the one side having the port, and wherein at least one of a length or a width of the port corresponds to an integer multiple of half a wavelength of sound associated with the second resonant frequency.

5. The apparatus of claim 1, wherein limiting the spectral density of the audio content at the first resonant frequency comprises reducing the spectral density of the audio content in at least one frequency range within a full width of the first resonant frequency.

6. The apparatus of claim 1, wherein the first resonant frequency is in a range between 300Hz and 1.5 kHz.

7. The device of claim 1, wherein the speaker is a micro-speaker comprising a sound emitting diaphragm, wherein the sound emitting diaphragm has a circumference of less than 5 inches.

8. An apparatus for processing a signal having audio content, comprising:

a source for generating a signal having audio content;

a spectral analyzer to determine a first value representative of a spectral density of the audio content at a first resonant frequency, wherein the first resonant frequency is associated with mechanical motion of: (i) a speaker diaphragm; or (ii) a mechanical support for the loudspeaker diaphragm, the spectrum analyzer further to determine a second value representative of a spectral density of the audio content at a second resonant frequency, wherein the second resonant frequency is associated with a port of a loudspeaker assembly; and

a notch filter for modifying the signal by limiting a spectral density of the audio content at the first resonant frequency in view of the first value and the second value.

9. The apparatus of claim 8, further comprising a memory device to store speaker calibration data comprising a threshold level of spectral density of the audio content at the first resonance frequency sufficient to mask buzzes of the speaker assembly at the second resonance frequency.

10. The apparatus of claim 9, wherein the notch filter is a dynamic notch filter having adjustable parameters, the apparatus further comprising a controller to modify the adjustable parameters of the dynamic notch filter in response to the first value, the second value, and the speaker calibration data.

11. The apparatus of claim 10, wherein the adjustable parameter of the dynamic notch filter comprises a strength of the dynamic notch filter.

12. The apparatus of claim 11, wherein the adjustable parameter of the notch filter comprises a width of the dynamic notch filter.

13. A method for reducing buzzes in a speaker, the method comprising:

obtaining a signal having audio content;

determining a first value representative of a spectral density of the audio content at a first resonant frequency, wherein the first resonant frequency is associated with mechanical motion of: (i) a speaker diaphragm; or (ii) a mechanical support for the loudspeaker diaphragm;

determining a second value representative of a spectral density of the audio content at a second resonant frequency, wherein the second resonant frequency is associated with a port of a speaker assembly;

determining, in response to the first value and the second value, that the signal will produce a beep of the speaker at the second resonant frequency;

generating a modified signal by limiting the spectral density of the audio content at the first resonant frequency to an extent determined in response to the first value and the second value; and is

Providing the modified signal to the speaker.

14. The method of claim 13, wherein determining that the signal is to produce a beep comprises retrieving speaker calibration data from memory, the speaker calibration data comprising a threshold level of spectral density of the audio content at the first resonance frequency, the threshold level sufficient to produce a beep of the speaker at the second resonance frequency.

15. The method of claim 13, wherein generating the modified signal comprises transmitting the signal through a static notch filter.

16. The method of claim 13, wherein generating the modified signal comprises sending the signal through a dynamic notch filter having adjustable parameters.

17. The method of claim 16, wherein the adjustable parameter comprises a strength of the dynamic notch filter, and wherein generating the modified signal further comprises adjusting the strength of the dynamic notch filter in response to the first value, the second value, and speaker calibration data.

18. The method of claim 17, wherein the adjustable parameter comprises a width of the dynamic notch filter, and wherein generating the modified signal further comprises adjusting the width of the dynamic notch filter in response to the first value, the second value, and the speaker calibration data.

19. The method of claim 13, wherein determining the first value and the second value is repeated after a set time interval.

20. The method of claim 13, wherein limiting the spectral density of the audio content at the first resonant frequency comprises reducing spectral density in at least one frequency range over the full width of the first resonant frequency.