Perceptual power reduction system and method

A method of reducing power consumed by an audio playback system includes: receiving a signal from a digital audio interface; comparing a sound pressure level (SPL) response of a first frequency band of the signal to a total SPL response of the signal, the first frequency band including frequencies lower than a selected frequency; and attenuating signal components in the first frequency band of the signal based upon the comparison of the SPL response of the first frequency band of the signal to the total SPL response of the signal.

BACKGROUND

The principle of audio masking can be leveraged to reduce power consumption in an audio playback system. For example, audio signals at frequencies that are masked by other frequencies may be attenuated to reduce overall power consumption. However, this approach alone may not result in very significant power savings and can introduce measurable and possibly audible sound pressure level (SPL) reductions. There is a need for power reduction techniques that take SPL into account.

DETAILED DESCRIPTION

Overview

Psychoacoustics describe how a listener (e.g., an average human listener) perceives sounds. In particular, the psychoacoustics principle of “auditory masking” means that during audio playback (e.g., playback of music, speech, or any other synthesized or recorded sound) there may be frequencies that are at least partially or completely masked by other frequencies and are therefore rendered inaudible (i.e., cannot be heard by an average listener). As used herein, a threshold for a “listener” or an “average listener” generally refers to a threshold for one or more audio parameters (e.g., frequency, amplitude, SPL, etc.), where the threshold can be arbitrarily set (e.g., by the listener) and/or determined based upon a calculation that is specific to a listener, and/or based upon a predetermined statistical average. The masked frequencies are good candidates for attenuation to save overall power during music playback because their removal will reduce hardware operations (e.g., filtering, amplification, and/or other signal processing) without having a negative impact on the audio quality perceived by the listener.

It has also been found that some loudspeakers (e.g., small loudspeakers, such as those used for headphones and other personal listening devices) cannot reproduce low frequencies efficiently. Accordingly, low frequencies (e.g., below a threshold frequency) can also be attenuated to save power consumption without affecting (or by only minimally affecting) the listening experience of an average user.

A system and method are disclosed for reducing power consumed by an audio playback system (e.g., power consumed by circuitry and/or a processor executing one or more software modules) by utilizing the principles of auditory masking and taking into account speaker SPL response. The system attenuates signal components at frequencies that do not produce a perceptible auditory response for average human listeners. In embodiments, the system includes a controller that receives a signal from a digital audio interface. The controller is configured to compare a SPL response of a first frequency band (sometimes referred to herein as the “low band” or “low frequency band”) of the signal to a total SPL response of the signal. The first frequency band can include signal components at frequencies lower than a selected (e.g., predetermined threshold) frequency. The controller is further configured to attenuate the signal components in the first frequency band of the signal based upon the comparison of the SPL response of the first frequency band of the signal to the total SPL response of the signal. For example, the controller can be configured to compare the SPL response of the first frequency band of the signal to the total SPL response of the signal by determining a ratio of the SPL response of the first frequency band of the signal to the total SPL response of the signal and comparing the determined ratio to a threshold ratio. In some implementations, the ratio is determined based on root mean square (RMS) values for the SPL response of the first frequency band and the total SPL response of the signal. The signal components in the first frequency band of the signal may be attenuated when the determined ratio is less than the threshold ratio.

Example Implementations

FIGS. 1A through 1Dillustrate an audio playback system100in accordance with various embodiments of this disclosure. Those skilled in the art will appreciate that the embodiments illustrated in the drawings and/or described herein may be fully or partially combined to result in additional embodiments. Substitutions and other modifications can also be made without departing from the scope of this disclosure. Accordingly, the illustrated and described embodiments should be understood as explanatory and not as limitations of the present disclosure.

FIG. 1Ais a schematic depiction of an audio playback system100in accordance with an example embodiment of this disclosure. As shown, the audio playback system100includes an expander104that controls the gain level of a signal from a digital audio input/interface (DAI)102prior to filtering. For example, the expander104includes and/or controls an amplifier and/or attenuator coupled to the DAI102. The expander104is configured to control a gain level of a signal or portions thereof (e.g., various signal components) after the signal is fed into the audio playback system100from the DAI102. In some embodiments, the expander104is configured to attenuate signal components below a predetermined minimum frequency or above a predetermined maximum frequency.

The DAI102can be communicatively coupled to an audio source101(e.g., a mobile device (e.g., smartphone, tablet, smartwatch, activity tracker, digital camera, notebook computer, portable media player, portable gaming device, portable storage device, etc.), an audio receiver, a television, a personal computer, or the like). For example, the audio playback system100can be incorporated within the audio source101or can be communicatively coupled to the audio source101by a wired or wireless connection. In embodiments, the DAI102can include, but is not limited to, an audio input jack/pin, a wireless receiver/transceiver, a magnetic or optical receiver or read head, or any combination thereof.

The audio playback system100further includes one or more filters106, for example, the system100can include a digital signal processing (DSP) core (including one or more infinite impulse response (IIR) filters), a cascaded integrator-comb (CIC) filter stage, and possibly other filters. These filters106may process the signal before it is fed into a digital-to-analog converter (DAC)110that outputs the audio signal to a speaker amplifier112coupled with an output device114(e.g., a loudspeaker, mini-loudspeaker, micro-loudspeaker, audio transmitter, or the like). In some embodiments, the audio playback system100further includes a sigma-delta modulator (SDM)108that is configured to encode the signal before it is fed into the DAC110.

The audio playback system100further includes a controller116configured to execute one or more modules121that cause the controller to selectively attenuate signal components based on an SPL response of a signal components within a first frequency band having frequencies below a selected frequency. For example, the controller116is configured to receive a signal from the DAI102. The controller116is configured to filter or otherwise isolate signal components in a first frequency band of the signal. For example, the controller116can be configured to apply a low pass filter that isolates signal components in the first frequency band (e.g., signal components having frequencies below a selected frequency). In some implementations, the selected frequency is less than or equal to 1 kHz, for example, the selected frequency can include a frequency approximately in the range of 50 to 500 Hz or more particularly 100 Hz to 300 Hz. The selected frequency may additionally or alternatively be based on a speaker SPL response of the audio playback system100. For example, the selected frequency can be based on a comparison of speaker SPL response to threshold of human hearing for an average person, or possibly for a demographic or even for a particular individual (e.g., based on a user input/selection). For example,FIG. 2includes a plot200that graphically depicts examples of a speaker SPL response202in comparison to curve representing threshold of human hearing204(e.g., for an average listener) at various frequencies. The selected frequency can include a frequency206, where the speaker SPL response202is less than the threshold of human hearing204at the frequencies below frequency206(e.g., approximately 300 kHz inFIG. 2). The speaker SPL response202can be a known or predetermined response (e.g., based on a particular product model and/or predetermined signal parameters).

After filtering out or otherwise isolating the signal components in the first frequency band, the controller116is configured to compare a SPL response of the first frequency band of the signal to a total SPL response of the signal. In embodiments, the controller116is configured to determine a ratio of the SPL response of the first frequency band of the signal to the total SPL response of the signal and compare the determined ratio to a threshold ratio (e.g., a predetermined threshold ratio and/or a threshold ratio based on a speaker SPL response (e.g., speaker SPL response202)). In some implementations, the threshold ratio is approximately in the range of −30 dB to −20 dB. The threshold ratio can additionally or alternatively be based on the SPL response of the audio playback system. For example, the threshold ratio can be based on a dynamic range of the speaker SPL response. In some embodiments, the determined ratio is based on RMS values of the SPL response of the first frequency band of the signal and the total SPL response of the signal. For example, the controller116can be configured to determine a RMS value of the SPL response of the first frequency band and an RMS value of the total SPL response, where the determined ratio is a ratio of the RMS value of the SPL response of the first frequency band of the signal to the RMS value of the total SPL response of the signal.

The controller116is further configured to attenuate signal components in the first frequency band of the signal based upon the comparison of the SPL response of the first frequency band of the signal to the total SPL response of the signal. For example, the controller116can be configured to attenuate the signal components in the first frequency band of the signal when the determined ratio is less than the threshold ratio. When the determined ratio is lower than the threshold ratio, the controller116can be configured to attenuate the signal components in the first frequency band to zero, near zero (e.g., attenuate the signal components in the first frequency band to be substantially zero), or completely remove (e.g., filter out or delete) the signal components in the first frequency band from the signal. When the determined ratio is greater than the threshold ratio, the controller116is configured to preserve the signal components in the first frequency band because removing them may affect the audio perceived by the listener. The controller116can be configured to preserve signal components in a second frequency band (e.g., signal components having frequencies above the selected frequency) when the controller116initially filters out or otherwise isolates the signal components in the first frequency band. The controller116may be further configured to generate an output signal by adding (e.g., rejoining) the signal components in the first frequency band of the signal and the signal components in the second frequency band of the signal when the determined ratio is greater than the threshold ratio.

In some embodiments, the output device114comprises a miniature speaker or micro-speaker, and the speaker amplifier112may be optimized for use with a mini or micro-speaker. For example, the audio playback system100may be designed for a mobile device (e.g., portable media player, smartphone, tablet, smartwatch, notebook computer, or the like). As previously noted herein, it has been found that small loudspeakers cannot reproduce low frequencies efficiently. Additionally, low frequency signal components may be masked by higher frequency components anyway. Taking these two factors into account, the audio playback system100can be configured to attenuate (e.g., reduce to zero or completely remove) or filter out these signal components without diminishing the listening experience of an average user. This is shown inFIG. 2, where an example of a small loudspeaker SPL is illustrated in comparison with threshold of human hearing. As can be seen, at low frequencies (e.g., below approximately 300 Hz inFIG. 2), the speaker SPL is so low that an average person cannot hear many of the signals being produced anyway. Accordingly, cutting them out has little to no effect on the audio being heard from the loudspeaker. In some cases, this can result in a power savings of up to 10% or more without any negative effect on the user's listening experience. In some embodiments, the controller116is further configured to attenuate signal components above a second selected frequency (too high for most humans to hear) in order to further reduce power consumption by the audio playback system100. For example, as shown inFIG. 2, signal components having frequencies above a second (higher) selected frequency208(e.g., above approximately 20 kHz inFIG. 2) may be too high frequency for most listeners to hear, and therefore these signal components can also be attenuated without affecting the user listening experience. This can also result in a potential power savings (e.g., up to 5% or higher in some cases), but typically not as significant of a reduction in power consumption as the power savings that results from attenuating masked low frequency signal components (e.g., in the manner described above).

In an embodiment, the controller116is in a signal path defined by other components (e.g., expander104, filters106, SDM108, and/or DAC110) of the audio system100. For example, as shown inFIG. 1A, the controller116can be coupled to and/or included within the expander104. The controller116may alternatively be disposed at another position in the signal path and/or included within another component (e.g., filter(s)106, for example, the controller116can include or can be part of a digital signal processor that implements the filter(s)106). In another embodiment that is illustrated inFIG. 1B, some or all of the audio playback system100components (e.g., expander104, filters106, SDM108, DAC110, any combination thereof, and so forth) can be implemented by the controller116. For example, the controller116can be configured to execute modules121that cause the controller to perform operations of the expander104, filters106, SDM108, and/or DAC110. In yet another embodiment that is illustrated inFIG. 1D, the controller116can be part of the amplifier112. For example, the controller116can include or can be part of logic for the amplifier112. In this regard, some or all of the signal path can be integrated with the amplifier112. The embodiments illustrated inFIGS. 1A, 1B, and 1Dcan be at least partially combined, for example, at least one portion of the signal path can be implemented by one or more discrete components and at least one portion of the signal path can be implemented within the controller116and/or amplifier112.

As shown inFIG. 1C, the controller116can include a processor118, a memory120, and a communications interface122. The processor118provides processing functionality for at least the audio playback system100/controller116and can include any number of microprocessors, digital signal processors, micro-controllers, circuitry, field programmable gate array (FPGA) or other processing systems, and resident or external memory for storing data, executable code, and other information accessed or generated by the audio playback system100/controller116. The processor118can execute one or more software modules121embodied in a non-transitory computer readable medium that implement techniques described herein. The processor118is not limited by the materials from which it is formed or the processing mechanisms employed therein and, as such, can be implemented via semiconductor(s) and/or transistors (e.g., using electronic integrated circuit (IC) components), and so forth.

The memory120can be an example of tangible, computer-readable storage medium that provides storage functionality to store various data and or program code associated with operation of the audio playback system100/controller116, such as software modules121and/or code segments, or other data to instruct the processor118, and possibly other components of the audio playback system100/controller116, to perform the functionality described herein. Thus, the memory120can store data, such as a program of instructions (e.g., modules121) for operating the audio playback system100(including its components), and so forth. It should be noted that while a single memory120is described, a wide variety of types and combinations of memory (e.g., tangible, non-transitory memory) can be employed. The memory120can be integral with the processor118, can comprise stand-alone memory, or can be a combination of both.

Some examples of the memory120can include removable and non-removable memory components, such as random-access memory (RAM), read-only memory (ROM), flash memory (e.g., a secure digital (SD) memory card, a mini-SD memory card, and/or a micro-SD memory card), magnetic memory, optical memory, universal serial bus (USB) memory devices, hard disk memory, external memory, and so forth. In implementations, the audio playback system100and/or the memory120can include removable integrated circuit card (ICC) memory, such as memory provided by a subscriber identity module (SIM) card, a universal subscriber identity module (USIM) card, a universal integrated circuit card (UICC), and so on.

The communications interface122can be operatively configured to communicate with components of the audio playback system100. For example, the communications interface122can be configured to transmit data for storage in the audio playback system100, retrieve data from storage in the audio playback system100, and so forth. The communications interface122can also be communicatively coupled with the processor118to facilitate data transfer between components of the audio playback system100and the processor118(e.g., for communicating inputs to the processor118received from a device (e.g., audio source101) communicatively coupled with the audio playback system100/controller116, e.g., via DAI102). It should be noted that while the communications interface122is described as a component of an audio playback system100/controller116, one or more components of the communications interface122can be implemented as external components communicatively coupled to the audio playback system100via a wired and/or wireless connection. The audio playback system100can also include and/or connect to one or more input/output (I/O) devices (e.g., via the communications interface122), such as a display, a mouse, a touchpad, a touchscreen, a keyboard, a microphone (e.g., for voice commands) and so on.

The communications interface122and/or the processor118can be configured to communicate with a variety of different networks, such as a wide-area cellular telephone network, such as a cellular network, a 3G cellular network, a 4G cellular network, or a global system for mobile communications (GSM) network; a wireless computer communications network, such as a WiFi network (e.g., a wireless local area network (WLAN) operated using IEEE 802.11 network standards); an ad-hoc wireless network, an internet; the Internet; a wide area network (WAN); a local area network (LAN); a personal area network (PAN) (e.g., a wireless personal area network (WPAN) operated using IEEE 802.15 network standards); a public telephone network; an extranet; an intranet; and so on. However, this list is provided by way of example only and is not meant to limit the present disclosure. Further, the communications interface122can be configured to communicate with a single network or multiple networks across different access points. In a specific embodiment, a communications interface122can transmit information from the controller116to an external device (e.g., a cell phone, a computer connected to a WiFi network, cloud storage, etc.). In another specific embodiment, a communications interface122can receive information from an external device (e.g., a cell phone, a computer connected to a WiFi network, cloud storage, etc.).

In embodiments, the communications interface122is configured to receive audio from an audio source101(e.g., a mobile device (e.g., smartphone, tablet, smartwatch, activity tracker, digital camera, notebook computer, portable media player, portable gaming device, portable storage device, etc.), an audio receiver, a television, a personal computer, or the like). For example, the communications interface122can include DAI102. The communications interface122/DAI102may be configured to receive audio signals from the audio source101via a communicative coupling. The communicative coupling can include a wired coupling, a wireless coupling (e.g., WiFi, Bluetooth, or the like), an optical fiber coupling, or the like.

Example Processes

FIGS. 3 and 4illustrate example processes300and400, respectively, for reducing power consumption of an audio playback system, such as the audio playback system100illustrated in any ofFIGS. 1A through 1D, or combinations thereof, by attenuating low frequency signal components based on SPL response of the audio playback system100. In general, operations of disclosed processes (e.g., process300and/or process400) may be performed in an arbitrary order, unless otherwise provided in the claims.

As shown inFIG. 3, a process300for reducing power consumed by an audio playback system (e.g., audio playback system100) includes receiving a signal from a DAI (block302). For example, the controller116can receive a signal from DAI102. In some implementations, the signal is at least partially processed (e.g., partially attenuated, amplified, filtered and/or modulated) prior to being received at the controller116. The signal can additionally or alternatively be at least partially processed after being processed by the controller116(e.g., after a controller116performs power savings operations described herein (e.g., blocks304and306) on the signal. A SPL response of a first frequency band of the signal is then compared to a total SPL response of the signal (block304). For example, the controller116can filter out high frequency components or otherwise extract/isolate signal components in a first frequency band that includes frequencies lower than a selected frequency. The controller116can then compare the SPL response of the first frequency band to the total SPL response of the signal. Based on this comparison, the controller116may attenuate signal components in the first frequency band of the signal (block306). For example, the controller116may be configured to attenuate the signal components in the first frequency band of the signal based on a determined ratio of power levels, averages, aggregations/integrations, or other measurements or calculations associated with the SPL responses of the first frequency band and the total signal in comparison to one another. It is noted that, in some instances, the “total signal” can refer to a range of frequencies having a lower and upper cutoff frequency. For example, the total signal can be based on a dynamic range (e.g., effective dynamic range) of the audio playback system100. In some implementations, the controller116is configured to attenuate the signal components in the first frequency band of the signal when a determined ratio of RMS values for the SPL response of the first frequency band and the total SPL response of the signal is less than a threshold ratio (e.g., a predetermined threshold ratio and/or a threshold ratio based on one or more parameters (e.g., SPL speaker response) of the audio playback system100).

The process400illustrated inFIG. 4is an example implementation of the process300illustrated inFIG. 3, where the signal components in the first frequency band are attenuated based on RMS values for the SPL response of the first frequency band and the total SPL response of the signal. The process includes receiving an input signal401(e.g., at controller116from DAI102). The signal401is sent through two paths. In a first path, the signal401is filtered by a low pass filter (e.g., a low pass filter applied to the signal401by controller116) that extracts signal components403in the first frequency band (e.g., signal components having frequencies less than the selected frequency) (block402). The remaining signal components (i.e., signal components405in a second frequency band having frequencies greater than the selected frequency) may be preserved to be later included in an output signal (e.g., in an output signal generated at block420or422). The signal components403in the first frequency band are filtered by an SPL filter (e.g., an SPL filter or determination module applied to the signal components403by controller116) that converts the signal components403into an SPL response for the first frequency band (block404). The controller116then calculates a RMS value of the SPL response of the first frequency band (block406). Similar operations are performed on the total (or near total) input signal401. The signal401is filtered by an SPL filter (e.g., an SPL filter or determination module performed by controller116) that converts the signal401into a SPL response of the signal401(often referred to herein as the “total SPL response” of the signal401) (block408). The controller116then calculates a RMS value of the total SPL response of the signal401(block410).

After calculating RMS values for the SPL response of the first frequency band and the total SPL response of the signal, the controller116determines a ratio of the RMS value of the SPL response of the first frequency band to the RMS value of the total SPL response of the signal (e.g., “Low SPL RMS”/“Total SPL RMS”) (block412). The controller116compares the determined ratio (e.g., “Low SPL RMS”/“Total SPL RMS”) to a threshold ratio, which may be selected, predetermined, and/or based on the speaker SPL response (block414). When the determined ratio is below the threshold ratio, the controller116attenuates the signal components403in the first frequency band (sometimes referred to as the “low band” signal components) (block416). For example, the controller116can reduce the gain values of signal components in the first frequency band to zero, near zero (e.g., attenuate the signal components in the first frequency band to be substantially zero), or at least partially filter or otherwise eliminate them from the final output signal. In some implementations, the controller116generates the output signal including the signal components405in the second frequency band (e.g., the remaining “high band” signal components) (block418). When the determined ratio is not below the threshold ratio, the controller116leaves the signal components403in the first frequency band intact; that is, the low band signal components (signal components403) are not attenuated by the controller116(block420). In such cases, the controller116may generate the output signal by adding the low band signal components403to the high band signal components405(effectively recreating the input signal401) (block422). In some implementations, the controller116preserves the input signal401or a copy of the input signal401and generates the output signal by simply outputting the preserved signal401instead of having to add the low band signal components403back to the high band signal components405.

Generally, any of the functions described herein can be implemented using hardware (e.g., fixed logic circuitry such as integrated circuits), software, firmware, manual processing, or a combination thereof. Thus, the blocks discussed in the above disclosure generally represent hardware (e.g., fixed logic circuitry such as integrated circuits), software, firmware, or a combination thereof. In the instance of a hardware configuration, the various blocks discussed in the above disclosure may be implemented as integrated circuits along with other functionality. Such integrated circuits may include all of the functions of a given block, system, or circuit, or a portion of the functions of the block, system, or circuit. Further, elements of the blocks, systems, or circuits may be implemented across multiple integrated circuits. Such integrated circuits may comprise various integrated circuits, including, but not necessarily limited to: a monolithic integrated circuit, a flip chip integrated circuit, a multichip module integrated circuit, and/or a mixed signal integrated circuit. In the instance of a software implementation, the various blocks discussed in the above disclosure represent executable instructions (e.g., software modules121) that perform specified tasks when executed on a processor. These executable instructions can be stored in one or more tangible computer readable media. In some such instances, the entire system, block, or circuit may be implemented using its software or firmware equivalent. In other instances, one part of a given system, block, or circuit may be implemented in software or firmware, while other parts are implemented in hardware.

It is to be understood that the present application is defined by the appended claims. Although embodiments of the present application have been illustrated and described herein, it is apparent that various modifications may be made by those skilled in the art without departing from the scope and spirit of this disclosure.