Piezoelectric MEMS device with adaptive threshold for acoustic stimulus detection

Abstract

A device is described that includes an adaptive acoustic detection circuit and an acoustic sensor device such as a microphone. In addition to the sensor, the device further includes a circuit configured to detect when an input stimulus of the sensor meets an adaptive threshold and further configured to generate a signal upon detection that causes a performance adjustment of the device, where the adaptive threshold is a threshold that varies over time based on detected changes in the sound of the environment in which the device is located.

Description

[0001] Claiming priority

[0002] This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 62 / 818,140, filed on March 14, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to acoustic sensing, and in particular to the use of sensors such as microphones as used in voice-activated devices such as smart speakers and other types of sound-activated devices. Background Art

[0004] With the development of the Internet of Things and the increasing use of acoustically activated devices, one of the challenges facing acoustically activated devices is to reduce power consumption. Generally, acoustic sensing devices sense acoustic signals (sound, vibration, etc.) that may occur at infrequent time intervals. In order to address the power consumption problem of acoustically activated devices, one method is acoustic wake-up detection. In the case of acoustic wake-up detection, an acoustic detector circuit is typically included in the acoustically activated device and remains in an active state that consumes power, while the rest of the acoustically activated device is in a shut-down or dormant state. When the acoustic detector circuit detects an event, the acoustic detector circuit generates a signal that causes power to be switched to the rest of the acoustically activated device. The acoustic detector circuit can also be an algorithm executed by a processor. A piezoelectric transducer is an electroacoustic transducer that converts an electric charge (e.g., generated by sound or input pressure) into energy. Summary of the Invention

[0005] According to one aspect, a device includes: a sensor element; and a circuit configured to detect when an input stimulus to the sensor satisfies an adaptive threshold, and further configured to generate a signal that causes a performance adjustment of the device upon detection, wherein the adaptive threshold is a threshold that varies over time based on detected changes in the sound environment in which the device is located.

[0006] The implementation may include one or more of the following features, or a combination of two or more of the following features. The circuit may be a first circuit, and the device may further include: a second circuit for processing the input after detection, wherein the second circuit is configured to increase the power level of the second circuit after detection relative to the power level of the second circuit before detection. The device may also be configured to output data representing one or more sound levels before detecting an input stimulus that meets the adaptive threshold. The output data may represent multiple sound levels in frequency or time. The device may further include: an amplifier circuit configured to track a sub-threshold sound signal in the environment of the device, a threshold sound signal in the environment of the device, and a supra-threshold sound signal in the environment of the device. The amplifier circuit may also sum the sub-threshold sound signal in the environment of the device, the threshold sound signal in the environment of the device, and the supra-threshold sound signal in the environment of the device.

[0007] In some implementations, the circuit may include: an amplifier configured to apply a gain to the input stimulus to amplify the input stimulus, wherein the gain is the sum of the sub-threshold sound signal in the environment of the device, the threshold sound signal in the environment of the device, and the supra-threshold sound signal in the environment of the device. The circuit may include: a bandpass filter bank including a plurality of filters to enable the adaptive threshold to be adaptive in different frequency bands. The circuit includes: an RMS-to-DC converter configured to receive the input stimulus; and an amplifier configured to: receive the input stimulus from the RMS-to-DC converter and amplify the input signal according to the background sound level. The circuit may be configured to detect sound signals in multiple frequency bands and is also configured to detect when the sound levels of at least a plurality of the sound signals in the multiple frequency bands increase or decrease relative to the sound levels of other sound signals detected at a previous time within a specified time period. For example, the circuit may be configured to increase the value of the adaptive threshold when the sound levels of at least a plurality of the sound signals in the multiple frequency bands increase within the specified time period, wherein the increased value corresponds to the detected increase in the sound level; and decrease the value of the adaptive threshold when the sound levels of at least a plurality of the sound signals in the multiple frequency bands decrease within the specified time period, wherein the decreased value corresponds to the detected decrease in the sound level. The adaptive threshold may be a non-fixed threshold. The device may be a microphone, an acoustic transducer, or a MEMS piezoelectric transducer.

[0008] According to another aspect, an adaptive acoustic detection circuit for detecting when an input stimulus to a sensor meets an adaptive threshold, the detection circuit comprising: a band-pass filter for receiving an output from the sensor; and a circuit fed with the band-pass filter output and configured to: detect when the output of the sensor meets the adaptive threshold and generate, upon detection, a signal that causes an adjustment in the performance of the device, wherein the adaptive threshold varies over time in accordance with a gradual change in the detected stimulus in the environment in which the device is located.

[0009] Implementations may include one or more of the following features, or a combination of two or more of the following features. The circuit may further include: a converter circuit for converting a signal from the band-pass filter circuit into a substantially DC signal; a fixed-gain amplifier for amplifying the substantially DC signal; a threshold circuit for establishing a variable threshold level; and a comparator circuit having a first input fed by the amplified substantially DC signal and a second input fed by the variable threshold level to generate a detection signal based on the value of the amplified substantially DC signal relative to the value of the variable threshold level. The band-pass filter, the converter, and the fixed-gain amplifier may comprise a first channel of the circuit, and the circuit may further include: at least one additional channel including a band-pass filter, a converter, and a fixed-gain amplifier; and a summing amplifier for receiving the outputs from the first channel and the at least one additional channel to provide an output fed to the first input. The band-pass filters of the first channel and the at least one additional channel have passbands of different frequencies.

[0010] In some implementations, the circuit further includes: a variable-gain amplifier having an input for receiving an input signal, a control port, and an output for providing an amplified output signal; a comparator circuit having a first input coupled to the output of the variable-gain amplifier and a second input fed by a fixed threshold level signal to generate a detection signal based on the value of the amplified output signal relative to the fixed value of the threshold level; and a feedback circuit for generating a control signal that controls the gain of the variable-gain amplifier. The feedback circuit may include: a rectifier for converting a signal at the input of the converter circuit into a substantially DC signal; an analog-to-digital converter for converting the substantially DC signal into a digital signal; and control logic for receiving the digital signal and determining the value of the control signal fed to the control port of the variable-gain amplifier. The feedback circuit may include a low-pass filter coupled between the rectifier and the analog-to-digital converter. The circuit may further include a high-pass filter and a low-pass filter coupled in series between the output of the variable-gain amplifier and the input of the comparator circuit.

[0011] According to another aspect, a method includes detecting when an input stimulus to a sensor of a device satisfies one or more detection criteria, wherein at least one of the one or more detection criteria includes an adaptive threshold that varies over time based on detected changes in sound in an environment in which the device is located; generating a signal upon detection that causes a performance adjustment of the device by increasing a power level of a circuit of the device relative to a power level of the circuit prior to detection; and processing the input of the device using the circuit having the increased power level.

[0012] Implementations may include one of the following features or a combination of two or more of the following features. Data representing one or more sound levels in an environment in which the apparatus is located may be received; and the adaptive threshold may be adjusted based at least in part on the one or more sound levels and data representing previously detected sound levels in the environment of the apparatus. The one or more sound levels may include an average sound level in the environment of the apparatus over a specified amount of time. The one or more sound levels may include a first sound level corresponding to a first frequency band and a second sound level corresponding to a second frequency band, the first frequency band and the second frequency band including different frequencies. If at least one of the one or more sound levels increases relative to previously detected sound levels in the environment of the apparatus over a specified amount of time, the adaptive threshold may be increased, wherein the increase in the adaptive threshold corresponds to the detected increase in at least one of the one or more sound levels. If at least one of the one or more sound levels decreases relative to previously detected sound levels in the environment of the apparatus over a specified amount of time, the adaptive threshold may be decreased, wherein the decrease in the adaptive threshold corresponds to the detected decrease in at least one of the one or more sound levels. The data representing the one or more sound levels may be received prior to detecting the input stimulus. The device may include a microphone, an acoustic transducer, or a MEMS piezoelectric transducer.

[0013] Piezoelectric microelectromechanical system (MEMS) devices have the inherent ability to be actuated by stimuli even in the absence of a bias voltage to activate such piezoelectric devices, providing ultra-low power detection of a wide range of stimulus signals. Piezoelectric MEMS microphones can exploit this effect and can be included in circuits that will generate a signal based on a specified minimum (fixed) acoustic input level indicating that a (valid) acoustic stimulus has been detected, allowing the circuit to perform further actions, such as mode entry into a higher performance state, turning on other components within the system, starting digital acquisition to further study the acoustic stimulus, etc.

[0014] Using a fixed acoustic input level can result in poor performance in very noisy environments (because background noise may be continuously above the threshold, causing the device to continue consuming power) and very quiet environments (where natural speech levels are unlikely to exceed the threshold level).

[0015] Adaptive acoustic level (e.g., threshold) circuitry according to the above aspects provides greater accuracy in stimulus detection by raising the threshold in noisy environments and lowering the threshold in quiet environments. The threshold for the environment can be related to the average value of the background noise of the environment in which the device is located, or can be proportional to the average value of the background noise, or can be defined as a noise level above which the device signals the system.

[0016] In the case where the transducer device is used as a microphone, such a piezoelectric MEMS transducer device can be used in an adaptive wake-up sound signal detection circuit for electronic devices including virtual digital assistant devices, smart speakers, remote controls, security cameras, headphones, mobile phone microphones, etc. Alternatively, the transducer device can be a sensor device for sensing other physical quantities (e.g., heat, vibration, etc.). The adaptive threshold is adjusted to the background level rather than having a preset and fixed threshold, so that the detection circuit detects "relevant" events that are different from background noise.

[0017] Aspects include corresponding computer systems, apparatus, computer program products recorded on one or more computer storage devices, and methods.

[0018] The details of one or more embodiments of the present disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the present disclosure will become apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a block diagram of a device / system with adaptive wake-up sound detection circuitry.

[0020] Figure 2A 、 2B , 2C and Figure 3 is a block diagram of the adaptive detection circuit.

[0021] Figure 3A and 3B is Figure 2A 、 2B and Figure 3 Block diagram of the circuit used in .

[0022] Figures 4A - 4D is a graph of sound pressure level versus time for various scenarios.

[0023] Figure 5 、 5A-5C is a block diagram of a device including a detection circuit.

[0024] Figures 6A - 6B This is the block diagram of the detection circuit.

[0025] Figures 7A - 7B Graphs showing waveforms input to a detection circuit and output signals from the detection circuit.

[0026] Figures 8A - 8B and Figure 9 is a block diagram showing a detection circuit in the system.

[0027] Figure 10 It's a flow chart. DETAILED DESCRIPTION

[0028] Due to the piezoelectric effect of the materials used to implement the transducer, such as AlN, PZT, etc., piezoelectric microelectromechanical systems (MEMS) devices have the inherent ability to be actuated by stimulation even in the absence of a bias voltage for the transducer. Such physical properties enable piezoelectric MEMS devices to provide ultra-low-power detection of a wide range of stimulation signals and provide deeper integration of detection electronics within application-specific integrated circuits (ASICs), without the need for system-level dedicated electronics and additional blocks that are not optimized for transducer power performance.

[0029] MEMS condenser microphones require a charge pump to provide the polarization voltage for the backplate. This charge pump requires a clock and a reservoir capacitor to store the charge pumped onto the backplate. Multiple stages are required to boost the polarization voltage to the required level. During initial power-up, it takes time to reach the desired level, which depends on the clock frequency, the size of the reservoir capacitor, and the available source voltage.

[0030] Piezoelectric MEMS devices do not require a charge pump. Furthermore, as the stimulus induces mechanical stress, a charge generated by the piezoelectric effect is always generated. This charge can be converted to a voltage using ultra-low-power circuitry, and a simple gain circuit can be used to provide an output proportional to the mechanical stress induced on the piezoelectric MEMS device. This eliminates the need for higher voltages to achieve higher transducer sensitivity.

[0031] One particular application of a piezoelectric MEMS microphone and exploiting this effect is a circuit that generates a signal based on a specified minimum (fixed) acoustic input level indicating the detection of an acoustic stimulus (e.g., a keyword or phrase). The system and / or microphone can further utilize this signal to perform further actions, such as entering a higher performance mode, turning on other components within the system, or starting digital acquisition to further study the acoustic stimulus and identify its components.

[0032] Using a minimum fixed acoustic input level can result in poor performance in very noisy environments (because background noise may be continuously above the threshold, causing the device to continue consuming power) and very quiet environments (where natural speech levels are unlikely to exceed the threshold level).

[0033] Rather than having a fixed acoustic input level, an adaptive acoustic level (e.g., threshold) provides greater accuracy in stimulus detection by raising the threshold in noisy environments and lowering the threshold in quiet environments. As described herein, in some implementations of FIG. 2 , the threshold may be related to the average value of the background noise in the environment in which the device is located. In implementations such as FIG. 2 and FIG. Figure 3 In other implementations of some variations, the threshold may be proportional to the average value of the background noise. Figure 3 In the example of , the threshold may be approximately 4.6 times the average value. Alternatively, the threshold may be defined as a noise level above which the device signals the system (or changes D OUT value).

[0034] refer to Figure 1 , an electronic device (or system) 10 is shown as including a piezoelectric MEMS transducer device 12 ("transducer device 12"), more specifically a piezoelectric MEMS microphone. The transducer device 12 is coupled to an adaptive wake-up sound signal detection circuit 14 ("detection circuit 14"), which is coupled to a device circuit 15 that may include electronics for processing sound. The electronic device 10 may be any type of electronic device that uses the transducer device 12. Non-limiting examples of such electronic devices 10 include devices such as (Amazon.com) and (Amazon), etc. Virtual digital assistant devices, smart speakers, remote control security cameras, headphones, mobile phone microphones. The detection circuit 14 detects the input stimulus and outputs a signal D that powers the device circuit 15. OUT In this example, the detection circuit 14 is configured to detect input stimuli based on an adaptive threshold that increases or decreases depending on the sound level of the environment.

[0035] Detection circuit 14 provides a floating or dynamic threshold signal level (corresponding to the sound level) at which the device 10 ( Figure 1 ) adjusts operation from a lower power level (sleep state) to a higher power level (wake state), at which higher power level, the device 10 performs voice signal processing or speech detection based on acoustic signals received by the transducer device 12 (for example, when used as a microphone). Alternatively, the transducer device 12 may be a sensor device that senses other physical quantities (for example, heat, vibration, etc.).

[0036] Rather than having a preset and fixed sound level threshold (for transitioning the device 10 from a lower power level to a higher power level), the detection circuitry 14 has an adaptive threshold that adjusts to the background sound level, such that the detection circuitry 14 detects "relevant" auditory events, e.g., those events that are distinct from the background noise. Where the detector operates at a fixed threshold level, such a detector would be unable to adjust to changes in the background noise, particularly in environments with very loud background noise characteristics and very quiet background noise characteristics, and / or in environments that vary between very loud background noise characteristics and very quiet background noise characteristics, thereby resulting in reduced accuracy in detecting relevant auditory events.

[0037] In a loud noise environment, the transducer device 12 (e.g., a microphone) receives sound input, and the detection circuit 14 generates a signal that powers on the device circuit 15. In the event that the detection circuit 14 continuously detects the presence of an input stimulus (due to the loud noise environment), the device circuit 15 always remains in an awake mode, causing the device (or system) 10 to consume power, even though there is no real valid input stimulus (e.g., input such as a human voice command, etc.). In a quiet environment, natural speech levels generally do not wake up the device (or system) 10, making the device (or system) 10 appear to be unresponsive to the user. By using a detection circuit 14 with an adaptive threshold, the device (or system) 10 avoids remaining in a high power mode in a high noise environment, and also avoids missing relevant input stimuli such as sounds in a low acoustic level environment.

[0038] refer to Figure 2A , shows the detection circuit 14. The detection circuit 14 is an adaptive detection circuit, which is able to adapt the signal level (representation of sound). Figure 3 A variant of the detection circuit will be described which is able to adapt the signal level to different power levels in different frequency bands.

[0039] The detection circuit 14 includes a bandpass filter 20 and a root mean square (RMS) / direct current (DC) converter 21 that receives an input signal V generated, for example, as an output voltage signal from a transducer device 12 such as a microphone. in . The RMS / DC converter 21 converts V in The DC signal is converted to a DC signal level and fed to the amplifier circuit 22 to increase (or amplify) the amplitude of the DC signal by a specified amount.

[0040] Amplified DC signal V O is input to a logic circuit 24 configured to select the minimum value of a plurality of inputs. Another signal 26 representing a maximum threshold is also input to the logic circuit 24. The maximum threshold is or may be (see below for example) Figure 5Aa pre-specified fixed threshold calculated in the manner discussed etc.). The logic circuit 24 selects between the minimum (or lower value) of the amplified DC signal (V o ) and the maximum threshold V T to provide a signal V Tout as the threshold sound level. By doing so, the detection circuit 14 implements an adaptive threshold that increases as the background sound level increases and decreases as the background sound level decreases. Thus, the detection circuit 14 enables the device to detect relevant auditory events in both noisy background sound levels (without the system 10 including the detection circuit 14 remaining in a high power mode) and quieter background sound levels.

[0041] The detection circuit 14 also includes a comparator 26 (e.g., a latch comparator) that compares V in with V T . The output (D OUT ) of the comparator 26 is processed by the system 10 including the detection circuit 14 to determine whether to transition the system 10 from a low power mode to a high power mode. The determination of the minimum and maximum thresholds can be adjusted according to the principles discussed below.

[0042] In Figures 2A - 3 various examples, a comparator (e.g., comparator 26) compares an unbuffered signal as a pseudo "real-time" signal with a threshold. Digital implementations typically buffer a certain amount of data, so digital implementations do not need to be very fast. Thus, such digital implementations can divide digital data into windows (e.g., 20 milliseconds of data per window) and compare the average energy level in the current window with the average energy levels in several previous windows. In an analog implementation without buffered data, a 20 - millisecond delay may be an overly long delay. Therefore, analog implementations need to be faster than equivalent digital implementations. Thus, Figures 2A - 3 these circuits of Figure 1 compare the actual sound pressure waveform (which may include a filtered version of the sound pressure waveform) with the threshold. In this way,

[0043] the system of

[0044] will be woken up quickly enough to capture a wake - up word (or other valid event). In some examples, the detection circuit 14 also outputs a signal representing one or more sound levels before detecting an input stimulus that meets the adaptive threshold in different frequency bands. For example, the system 10 can be configured to report the background sound level (or energy) to one or more external systems before the detection circuit 14 detects an input stimulus and the system 12 is powered on.

[0044] Now referring to Figure 2B , an alternative detection circuit 14b is shown. The detection circuit 14b is configured to include an AND ( Figure 2AThe present invention also includes a plurality of channels 11a-11n corresponding to the detection circuit 14a of the present invention, and further includes a summing amplifier 30, which sums the input signals from the plurality of channels 11a-11n (as described above, each channel includes a corresponding bandpass filter 20, a root mean square (RMS) / direct current (DC) converter and an amplifier circuit 22) to provide a summed Vin signal that is compared with a threshold value.

[0045] Referring to FIG2c, another alternative detection circuit 14c is shown. The detection circuit 14c is an adaptive detection circuit that adapts the threshold to changes in the input signal level (e.g., a representation of sound or other acoustic input). The detection circuit 14c is an adaptive detection circuit that adapts the threshold to changes in the input signal level (e.g., a representation of sound or other acoustic input). Figure 2A 、 2B The detection circuits 14a-14b are similarly dynamically adaptive, but work in a different way to detect sound or acoustics. The alternative detection circuit 14c includes an amplifier 25a with a fixed gain amount that is fed with an input signal (e.g., from an input sensing device such as a microphone), which is amplified by a nominal gain amount. The amplified signal is fed to a high pass filter 25b to filter out unwanted DC offset voltages and remove very low frequency components that are not of interest. The output of the high pass filter 25b is fed to a variable gain amplifier 25c having an input, an output, and a control input. The output of the variable gain amplifier 25c is an amplified signal. The control signal provided by the feedback loop 28 controls the gain applied to the output signal of the variable gain amplifier 25c.

[0046] The output amplified signal from variable gain amplifier 25c is coupled to a low-pass filter 25d and a high-pass filter 25e, which are placed together to form a bandpass filter. These filters 25d, 25e can remove unwanted DC offsets if necessary and can be used to filter out unwanted portions of the signal depending on the application. The signal is fed to, for example, the positive input of comparator 27 and compared to a fixed threshold 29 located at, for example, the negative input of comparator 27. Although the signal is compared to a fixed value in this case, the threshold is actually floating because the gain of the signal applied to the output of amplifier 25c is controlled by a feedback loop 28, which includes a rectifier circuit 28a, another low-pass filter 28b, an analog-to-digital converter 28c (e.g., a three-bit analog-to-digital converter), and control logic 28d that generates a control signal to control the gain of variable gain amplifier 25c.

[0047] As shown, a feedback loop 28 is coupled to the input of the comparator 27. This signal is fed to a rectifier 28a and the rectified signal from the rectifier 28a is fed to a low pass filter 28b (for Figure 2A) to provide a pseudo-RMS (root mean square) output signal value. This pseudo-RMS output signal is fed to a 3-bit ADC 28c to provide a 3-bit digital output, which is used to determine whether the signal level entering the input terminal of the comparator 27 is too high, too low, or within a set range. This digital output is fed to the control logic 28d, and the control logic determines the status of the input signal level. If the input signal to the comparator is too low, the ADC output is low, and this causes the control logic to generate a control signal that is fed to the variable gain amplifier 25c to increase the gain of the variable gain amplifier 25c. If the input signal to the comparator is too high, the ADC output is high, and this causes the control logic to generate a control signal that is fed to the variable gain amplifier 25c to reduce the gain of the variable gain amplifier 25c. If the signal is at an appropriate level, the control logic does not change the gain of the variable gain amplifier 25c.

[0048] Due to circuit timing, the control logic operates slowly and only changes the gain at, for example, half-second intervals (or other time increments). Thus, the gain responds only to slow changes in the input signal level. This feedback loop 28 controls the gain so that the RMS level entering the comparator 27 is approximately constant. Additionally, the gain value in the variable gain block is an indication of the sound level. This gain value can be communicated from the circuit 14c to the D OUT Provides an indication of the sound level before changing it.

[0049] Now refer to Figure 3 , the alternative adaptive detection circuit 14' is shown to include a plurality of channels, such as channel a to channel n. Channel a to channel n (CH1-CH n ) are each fed with an input signal from the input terminal 31, and channels CH1-CH n Each includes, for example, a transducer device 12 (eg, Figure 1 One of a plurality of bandpass filters 32a-32n such as a bandpass filter is provided between the microphone (e.g., a microphone) and the input 31 of the detection circuit 14'. Each of the bandpass filters (BPF) 32a-32n is tuned to a specific frequency band (e.g., configured according to human hearing, 20 Hz to 20,000 Hz). The detection circuit 14' has a plurality of channels CH a -CH n , and each channel provides an output signal.

[0050] Multiple channels CH a -CH n The signal compressors 34a-34n, half-wave rectifiers 36a-36n, low-pass filters 38a-38n and AGC circuits 40a-40n are included. In some implementations, the weighting circuits w a -wn , which can be used to weight the individual contributions from each channel according to the specific requirements of a given application of the detection circuit 14'. The signal compressors 34a - 34n compress the signals output from the respective band - pass filters 32a - 32n, and the half - wave rectifiers 36a - 36n convert the compressed band - pass input signals into DC values, enabling additional signal compression and envelope tracking. The low - pass filter can filter out higher frequency components, especially those outside the frequency band used for envelope tracking of input stimuli that are truly important (e.g., inputs such as human speech commands). The amplifier circuit 40a is capable of tracking sub - threshold activity as well as trans - threshold activity. In one embodiment, the AGC 40a is of the type described in "An Analog VLSI Implementation of the Inner Hair Cell and Auditory Nerve Using a Dual AGC Model" in the IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, Volume 8, Issue 2, April 2014, the entire content of which is incorporated herein by reference. In this specification, all the circuits disclosed operate in the analog domain. However, digital - signal - processing equivalents of these circuits can be alternative implementations and will operate in the digital domain. The threshold is nominally a fixed value that can gradually float or vary between a minimum limit and a maximum limit. The minimum threshold and the maximum threshold are empirically determined based on the tuning of circuits such as 32 - 40. The summer can be implemented as a common operational amplifier.

[0051] The detection circuit 14' further includes a threshold circuit 44 that implements a threshold algorithm to adjust the output threshold signal between a "minimum" value and a "maximum" value, thereby providing a reference value to a comparator 46 such as a latch comparator. The detection circuit 14' has an input for receiving a control signal that is used to adjust and tune the threshold between a "minimum" value and a "maximum" value (which can be a fixed value or a variable value) to provide a reference value to the latch comparator 46 at the output. In one embodiment, the input control signal for adjusting the output threshold is generated by feeding the input from the output of the summer 42 to the threshold circuit 44. In another embodiment, the signal is provided by a processor (not shown), which can be part of the wake - up circuit of the device 10 and / or the circuit.

[0052] The latch comparator 46 is fed by an input signal (or a single one of these signals) aggregated by the summer 42 from the input 31, so that the comparator 46 switches the state of the wake-up signal according to the relative values of the input signal at the + input of the comparator 46 and the threshold signal at the – input of the comparator 46. When the comparator 46 has an input signal at the input + that is equal to or higher than the threshold at the –, the comparator will trigger the high state of signal D OUT , which can be used as a wake-up signal for other circuits in the device / system 10.

[0053] In the detection circuit 14’, each channel CH a -Ch n is configured to detect a stimulus input in a specified frequency band for the channel, for example, based on the detected frequency of V in for that channel. The channels CH a -Ch n provide output signals S OUT1 to S OUTn . These signals can be aggregated by a summer 44 (e.g., an operational amplifier) to provide D OUT . (Alternatively, if the circuits of the device / system 10 also have multiple comparators not shown, a single one of the signals S OUT1 to S OUTn can be used to wake up the circuits of the device / system 10.) These signals S OUT1 to D OUTn can be used together for the processing of audio information. Each of the band-pass filter banks with multiple filters is tuned to a specific frequency band, which enables the detection circuit 14’ to adapt to different frequency bands.

[0054] In Figure 3 the embodiment, the circuits 32 - 40 provide a specially tuned spike rate function that can sum all sub-threshold and supra-threshold activities from all channels at the summing device 44 to provide a wake-up sound trigger signal to the system 10.

[0055] Figure 3A Shows a transistor-implemented logarithmic amplifier, which can be used as the compressor circuits 34a - 34n. Figure 3B Shows an implementation of the half-wave rectifiers 36a - 36n. These are merely illustrative examples for implementing these circuits 34a - 34n and 36a - 36n that can be used.

[0056] Reference , plot line 40 shows how the adaptive threshold 42 increases (over time) as the sound level (represented by waveform 44) increases over time in a particular environment. In this example, the adaptive threshold 42 is based on the history of the sound in the particular environment. Thus, the adaptive threshold 42 is adjusted according to the sound of the environment (e.g., the background sound level in the environment). As described herein, the adaptive threshold can be implemented in an analog circuit to achieve lower system power consumption (e.g., relative to the system power consumption with a fixed threshold). These adaptive thresholds can also be implemented in an application specific integrated circuit (ASIC) of a microphone (whether digital or analog circuit) to achieve low system power usage and flexibility compared to the system power usage and flexibility of a wake-up circuit with a fixed threshold. As further described herein, the energy level before "waking up" (e.g., the device is powered on) can be communicated to the rest of the system.

[0057] Reference Figure 4A , plot lines 50a - 50d show the sound waveforms of a person speaking. The red line (or dashed line) represents the threshold. Whenever the waveform exceeds the threshold, the microphone stays on for a period of time to ensure the capture of the entire utterance. Plot line 50a shows quiet background noise without speech. Plot line 50b shows moderate background noise without speech. Plot line 50c shows quiet background noise (~45 dB) and moderate speech level (~65 dB). Plot line 50d shows moderate background noise (~60 dB) and loud speech level (~75 dB).

[0058] In a device implementing a fixed threshold, the device operates as follows. In the case of quiet background noise (as shown in plot line 50a) or loud speech (as shown in plot line 50d), the performance is as expected. In the absence of speech, power is saved (as shown in plot line 50a). As shown in plot line 50d, in the presence of speech, keywords are captured.

[0059] However, as shown in plot line 50c, if the speech is exactly at a moderate level, the keyword is missed. Since the threshold is not exceeded until the middle of the first word rather than at the beginning of the first word, the keyword is missed. As shown in plot line 50b, if the background noise is moderate, the system does not save any power. This is because the noise alone exceeds the threshold. These latter two results (depicted in plot lines 50b, 50c) are not desirable. A threshold that is not fixed but is a function of the past background noise level is adaptive and can detect speech stimuli when the speech is at a moderate level and can also save power when the background noise is moderate.

[0060] Reference , the graph lines 52a - 52d provide examples of such an adaptive threshold. In each of these examples, the threshold (red line) is created by taking the RMS value of the first 100 milliseconds of audio and multiplying that value by 4.6. This threshold is referred to herein as "threshold #1". In these four examples, as shown in graph lines 52a - 52c, in 3 out of 4 scenarios, the behavior is as desired. As shown in graph lines 52a - 52b, in the absence of speech, since the threshold scales with the noise, power is saved in both cases. As shown in graph line 52c, in the presence of speech, since the speech signal - to - noise ratio (SNR) is good, keywords are captured for quieter situations. As shown in graph line 52d, in the case of louder background noise, since the SNR is slightly worse, the keywords are missed.

[0061] Reference Figure 4B , as shown in graph lines 54a - 54d, non - linearity is added to the threshold depicted in FIG. 4c to ensure good performance in the scenarios described above. In these examples, the threshold is the minimum of a fixed value such as 0.09 Pa and the RMS value multiplied by 4.6. As shown in graph lines 54a - 54d, the resulting threshold achieves the desired results in the scenarios described above. Further improvements to the algorithm are possible, and these specific levels are given only as examples. However, the adaptive threshold described herein scales with the input and non - linearity to handle loud background noise / poor signal - to - noise ratio.

[0062] The above implementation uses an auditory model to set the adaptive wake - up signal threshold of a sensor device such as a microphone. The adaptive auditory model discussed above can be implemented in an analog circuit to achieve very low power consumption, or it can also be implemented in the digital ASIC circuit of a microphone to achieve low power consumption and operational flexibility.

[0063] In , one technique for determining the threshold boundary uses the technique described below, which is adapted from PCT patent application PCT / US2017 / 019996, titled "A Piezoelectric MEMS Device for Producing a Signal Indicative of Detection of an Acoustic Stimulus", with publication number WO 2017 / 151650, filed on February 28, 2017.

[0064] Due to the piezoelectric effect of materials such as AlN and PZT used to implement the transducer, piezoelectric microelectromechanical systems (MEMS) devices have the inherent ability to be driven by stimulation even in the absence of a bias voltage for the transducer. This physical property enables piezoelectric MEMS devices to provide ultra-low-power detection of a wide range of stimulation signals and deeper integration of detection electronics within application-specific integrated circuits (ASICs), eliminating the need for system-level dedicated electronics or additional modules that are not optimized for transducer power performance.

[0065] MEMS condenser microphones require a charge pump to provide the polarization voltage for the backplate. This charge pump requires a clock and a reservoir capacitor to store the charge pumped onto the backplate. Multiple stages are required to boost the polarization voltage to the required level. During initial power-up, it takes time to reach the desired level, which depends on the clock frequency, the size of the reservoir capacitor, and the available source voltage.

[0066] Piezoelectric MEMS devices do not require a charge pump. Furthermore, as the stimulus induces mechanical stress, a charge generated by the piezoelectric effect is always generated. This charge can be converted to a voltage using ultra-low-power circuitry, and a simple gain circuit can be used to provide an output proportional to the mechanical stress induced on the piezoelectric MEMS device. This eliminates the need for higher voltages to achieve higher transducer sensitivity.

[0067] One specific application utilizing a piezoelectric MEMS microphone and exploiting this effect is a circuit that generates a signal based on a specified minimum acoustic input level indicating that an acoustic stimulus has been detected. The system and / or microphone can further utilize this signal to perform further actions, such as entering a higher performance mode, turning on other components within the system, or initiating digital acquisition to further study the acoustic stimulus and identify its components.

[0068] In an example, a detection circuit of an acoustic device such as a microphone is connected to a Figure 4C ) as part of the logic circuitry, rather than including an acoustic device that allows the application processor to execute logic detection pins (such as and Figure 4D (as shown). The detection circuit is designed to indicate when the input pressure stimulus reaches a specified level. The detection circuit triggers a digital state machine to indicate that a signal is being heard. The state machine causes the microphone ASIC to enter a higher-performance state. Due to the inherent startup advantage of the piezoelectric microphone, this state is achieved immediately. If the system is capable of entering sleep mode, the digital state machine can also signal the system to exit sleep mode and prepare for further processing of the signal. The microphone will contain the necessary logic to determine the surrounding acoustic environment and decide which action to take to further process the sensed acoustic environment.

[0069] In another example, and 5 As shown, the logic required on the simplified microphone ASIC is pushed to the application processor for the decision logic of the surrounding acoustic environment. Thus, the microphone ASIC simply implements a detection circuit where the detection level is set to the acoustic input level. Then, the ASIC latches acoustic events exceeding this threshold, signals the system, and allows the system to put the ASIC mode into a high-performance state to interrogate the surrounding acoustic environment in detail. The ASIC will implement this function by having dedicated inputs and dedicated digital outputs, where the dedicated inputs control which mode the ASIC is in, and the dedicated outputs signal the system when the microphone is in the wake-up sound mode and the acoustic stimulus has exceeded the detection threshold. Generally, the wake-up sound includes the following modes or configurations of devices (such as microphones, acoustic devices, acoustic transducers, acoustic piezoelectric transducers, piezoelectric devices, and MEMS microphones, etc.), where the device adjusts or transitions between states, modes, or actions in response to detecting a threshold input stimulus being met (e.g., an audio input at or above the threshold level). In another example, the wake-up sound includes a mode in which a device (e.g., including an acoustic transducer and / or an integrated circuit) is configured to detect an acoustic stimulus or detect the satisfaction of one or more criteria, and is also configured to perform one or more actions or make a transition between modes or states upon detection.

[0070] Refer to Figures 2A - 3, Circuit 100 includes transducer 102 and detector circuit 104. Source follower stage 106 converts the charge generated by transducer 102 and provides gain to the next stage (e.g., latch comparator stage). The second stage is latch comparator 108, which compares the output of source follower 106 with a reference voltage that is designed to target a specific minimum acoustic input sound pressure level (SPL). Once this level is sensed, latch comparator 108 latches the event and provides a signal indicating the event. The latch uses positive feedback to effectively act as a memory cell. Once the latch is powered off, the latched information is cleared or lost, while a memory such as a static random access memory (SRAM) retains information even when powered off. As described in further detail below, the provided signal is output to a detection pin that alerts an external system that the SPL has been detected. By driving this signal out of the chip, this signal can be further used to control / trigger other events within an application specific integrated circuit (ASIC) or within the overall system. In a variant, latch comparator 108 is configured to detect when an acoustic input (or VIN) meets one or more specified criteria. The detection circuit can be configured to detect various types of criteria. These criteria include, for example, voice criteria (detection of voice), keyword criteria (e.g., detection of a keyword), ultrasonic criteria (e.g., detection of ultrasonic activity near a transducer or acoustic device around us), and criteria for detecting footsteps, mechanical vibrations / resonances, gunshots, breaking glass, etc.

[0071] In this example, the bandwidth of the preamplifier stage (implemented by a preamplifier, for example) determines the spectrum of the input signal that triggers the comparator stage implemented by latch comparator 108. Ultra-low power electronics typically have a bandwidth where the audio range is still acceptable. Additionally, pulsed acoustic events trigger a broad spectrum increase in energy (acceptable for comparator triggering).

[0072] Further processing to discriminate specific frequencies and frequency bands is also implemented to provide the ability to detect specific acoustic features (i.e., command words, acoustic signals) at ultra-low power (as described in further detail below due to the external audio subsystem being powered off). Multiple devices (configured to wake up in sound mode) can also be implemented as an array. In this example, the DOUT / VOUT signal is processed to provide the ability to perform directional measurements, beamforming, beam steering, proximity detection, and signal-to-noise ratio improvement.

[0073] Reference , Device 200 implements wake-up sound in a configurable mode. In this example, device 200 includes an acoustic device. Device 200 includes switch 204, transducer 202, detection circuit 206 (e.g., detection circuit 14 in FIG. 2 or Figure 2Ba detection circuit 104), an integrated circuit (“IC”) 207 (hereinafter referred to as “IC” 207), and a preamplifier 208. In a variant, the IC 207 includes a gain circuit, an amplifier, or other circuits and does not include the preamplifier 208.

[0074] In this example, the preamplifier 208 is configured to process an audio input in an operating mode and is also configured to power on after detecting one or more specified criteria. The switch 204 is configured to switch the device 200 between a first mode (e.g., wake-up sound mode) and a second mode (e.g., normal or operating mode), for example, in response to receiving an instruction from a processor external to the device 200. The switch 204 includes pins 210, 212. Generally, a pin includes a pad (e.g., attached or mounted to a circuit). The pin 210 is a mode pin and is a dedicated input for controlling the mode of the device 200. The pin 212 is a voltage drain (VDD) pin that inputs the VDD of the device 200 to the switch 204. In this example, an external system (e.g., such as a processor 512 therein) controls the operating mode of the device 200 by sending a mode signal that sets mode = 1 (i.e., mode = VDD) to the mode pin 210 (which, for example, causes the device 200 to transition to a wake-up sound mode in which the detection circuit 206 is powered on by routing VDD to the detection circuit 206). In this example, the pin 210 includes a pad configured to receive a signal from an external processor that causes the device 200 to switch from a first mode (e.g., wake-up sound mode) to a second mode (e.g., operating mode). In this example, the first mode includes a mode in which the detection circuit 206 is substantially powered on and the preamplifier 208 is substantially powered off (e.g., completely powered off or in a state of consuming the least amount of power). In this example, the second mode includes a mode in which the preamplifier 208 is substantially powered on and the detection circuit 206 is substantially powered off. In this example, the device 200 is configured to switch from the first mode to the second mode when it detects that an input audio meets one or more criteria.

[0075] When mode pin 210 is set equal to 0 (via a mode signal), device 200 operates in an operating mode (e.g., normal mode) in which detection circuit 206 is powered down (or substantially powered down) and preamplifier 208 is powered up (or substantially powered up) by routing VDD to preamplifier 208. That is, a voltage equal to VDD causes IC 207 to enter a wake-up sound mode, while a floating or low signal causes IC 207 to enter a normal operating mode. The mode signal is buffered and further controls power switch 204, which routes VDD to either the high-performance circuitry (e.g., preamplifier 208) or the wake-up sound circuitry (e.g., detection circuit 206). The mode signal also configures the input bias circuitry (e.g., bias circuit 218) to control the switches (included therein), which appropriately configures the input bias network and switches for transducer 202.

[0076] In this example, the transducer 202 receives an acoustic input, and the transducer 202 converts the acoustic input into an input voltage (VIN). The detection circuit 206 detects when the acoustic input meets one or more criteria. In this example, the detection circuit 206 is configured to operate at approximately 5 microamperes. For example, the detection circuit 206 detects when VIN is equal to a threshold voltage or reference voltage (VREF), such as VIN=VREF. When it is detected that one or more detection criteria are met, the detection circuit 206 generates a signal that causes the detection pin 209 to become "high" (e.g., having a value equal to 1). There are various types of detection criteria. In an example, the detection criteria include an adjustable threshold. The adjustable threshold can be adjusted by software or one or more software updates and / or one or more circuit configurations and / or settings. In one example, the adjustable threshold includes an adaptive threshold based on a specified or recorded noise level for a particular geographic area.

[0077] In this example, the detection pin 209 includes a pad that is configured to send a signal to an external processor specifying that the acoustic input stimulus to the transducer 202 meets at least one of the one or more detection criteria. There are various types of acoustic input stimuli including, for example, sound and pressure. The external processor or system (e.g., Figure 2AThe processor 512) in receives the signal from the detection pin 209. As described in further detail below, in response to the signal, the external processor is powered on or powered up to an increased power level (relative to the power level before the processor received the signal). Additionally, in response to the signal, the processor sets the mode pin 210 to a low value to cause the device 200 to transition from the wake-up sound mode to the operating mode. In this example, the device 200 is configured to receive a signal from a processor external to the device 200 that is used to power down the detection circuit 206 and power up the preamplifier 208. In another example, the device 200 is configured to receive a signal from a processor external to the device that is used to reduce the power level of the detection circuit 206 relative to the power level of the detection circuit 206 before detection, and the signal is also used to increase the power level of the preamplifier 208 relative to the power level of the preamplifier 208 before detection.

[0078] In the operating mode, another circuit in the IC 207 (such as the preamplifier 208, etc.) increases the power level of its second circuit relative to the power level of the second circuit before detection. For example, in the operating mode, the preamplifier 208 is configured to operate in the range of 100 - 300 microamps. In this example, the signal generated by the detection circuit 206 causes a performance adjustment of the device 200 by causing the external processor to send an instruction to the device 200 to increase the power level of the second circuit (e.g., the preamplifier 208) relative to the power level of the second circuit before detection. In this example, the preamplifier 208 was substantially powered off before detection. Once in the operating mode, the device 200 processes the acoustic input 202 and outputs VOUT (e.g., pin 211) to an external processor or system for application processing. In this example, VOUT represents an output voltage amplified based on the voltage of the acoustic input.

[0079] In In a variant, the device 200 is an encapsulated device for mounting on a substrate or other circuit. The encapsulated device includes a substrate for mounting the acoustic piezoelectric transducer 202, the detection circuit 208, and the preamplifier 208 (or any other type of circuit). The encapsulated device includes a housing portion for covering the substrate on which the transducer 202, the detection circuit 208, and the preamplifier 208 (or any other type of circuit) are mounted.

[0080] Refer to Figure 5, device 220 is a variation of device 200. Device 220 includes logic circuit 222 (hereinafter referred to as "logic 222") and, for example, does not include detection pin 209. In this example, detection circuit 206 is configured to generate a signal when the acoustic input meets one or more criteria (programmed into the detection circuit or accessible or readable by the detection circuit). In this example, logic 222 is configured to implement a digital state machine. Detection circuit 206 sends a signal (indicating detection) to logic 222 to trigger the digital state machine. The state machine (in logic 222) causes IC 207 to switch mode to a higher performance state, for example, by energizing preamplifier 208 and deenergizing detection circuit 206. That is, logic 222 is configured to reduce the power level of detection circuit 206 relative to the power level of detection circuit 206 before detection, and to increase the power level of preamplifier 208 relative to the power level of preamplifier 208 before detection. Logic 222 includes configurable logic and / or software that can be configured to perform one or more specified tasks.

[0081] The logic 222 instructs the switch 204 to switch modes by sending a switch signal to the switch 204 that causes the mode pin 210 to go high or low. That is, the switch 204 is configured to switch from the first mode (e.g., wake-up sound mode) to the second mode (e.g., working mode) in response to receiving an instruction from the logic 222 of the device 220. If the system (e.g., The external processor 512 in the example can enter sleep mode, and the digital state machine also signals the system to exit sleep mode and prepare to further process the signal. In this example, the device 220 itself includes logic 222 for analyzing the surrounding acoustic environment and deciding which action to take to further process the sensed acoustic environment (e.g., by deciding whether to operate in wake-up sound mode or in working mode).

[0082] In this example, a detection circuit of an acoustic device such as a microphone is connected to a Figure 2A ) as part of the logic circuitry, rather than the acoustic device including a detection pin that allows the application processor to perform logic (such as (as shown). The detection circuit is designed to indicate when the input pressure stimulus reaches a specified level. The detection circuit triggers a digital state machine to indicate that a signal has been heard. The state machine causes the microphone ASIC to transition to a higher-performance state. Due to the inherent startup advantage of piezoelectric microphones, this state is achieved immediately. If the system is capable of entering sleep mode, the digital state machine can also signal the system to exit sleep mode and prepare for further processing of the signal. The microphone will contain the necessary logic to determine the surrounding acoustic environment and decide which action to take for further processing of the sensed acoustic environment.

[0083] In another example, as Figure 5 shown, the logic required on the simplified microphone ASIC is pushed to the application processor to make decisions about the surrounding acoustic environment. The microphone ASIC then simply implements a detection circuit where the detection level is set to the acoustic input level. The ASIC then latches acoustic events that exceed this threshold, signals the system, and allows the system to put the ASIC mode into a high-performance state to interrogate the surrounding acoustic environment in detail. The ASIC will implement this functionality with a dedicated input that controls which mode it is in and a dedicated digital output that signals the system when the microphone is in the wake-up sound mode and the acoustic stimulus has exceeded the detection threshold. Generally, wake-up sound includes the following modes or configurations of devices (such as microphones, acoustic devices, acoustic transducers, acoustic piezoelectric transducers, piezoelectric devices, and MEMS microphones, etc.), where the device adjusts or transitions between states, modes, or actions in response to detecting a threshold input stimulus being met (e.g., an audio input at or above a threshold level). In another example, wake-up sound includes a mode in which a device (e.g., including an acoustic transducer and / or an integrated circuit) is configured to detect an acoustic stimulus or detect the satisfaction of one or more criteria, and is also configured to perform one or more actions or make a transition between modes or states when detected.

[0084] Referring to Figure 5A FIG. [FIGURE NUMBER NOT PROVIDED], a variant is shown. In this variant, device 219 (e.g., a speaker, a smart speaker device, a smart speaker enclosure, etc.) includes a first circuit 217 and a second circuit 218 (e.g., including one or more microphones, DSP chips, etc. (e.g., in a smart speaker enclosure)). In this example, the second circuit 218 includes a circuit that is turned on by the first circuit 217. In this example, the second circuit 218 includes a circuit that is in a dormant or powered-off state. In this example, when the second circuit 218 is turned on, the second circuit 218 transitions from a lower power state to a higher power state (a power state relative to the lower power state). In this example, the first circuit 217 is configured to pattern or turn on all of the second circuit 218 or one or more parts of the second circuit 218. In this example, the first circuit 217 includes a sensor 215 for sensing, detecting, or receiving a sensed input 215a such as detecting motion, etc. The detection circuit 206, the biasing circuit 218, and the switch 204 are each configured to work substantially as described previously with respect to FIG. [FIGURE NUMBER NOT PROVIDED]. In this example, the first circuit is configured to operate at approximately 8 microamps. The second circuit is configured to operate using 20 - 350 microamps.

[0085] Please note that the figure numbers in the original text seem to be incomplete (e.g., refers to "FIG.", but the actual figure number is missing). The translation has been done as accurately as possible with the available information.For example, switch 204 is configured to switch a first circuit 217 between a first mode (e.g., wake-up sense input mode) and a second mode (e.g., normal or operating mode). Generally, the wake-up sense input mode includes a mode or configuration of the device in which the device adjusts or transitions between states, modes, or actions in response to detecting a threshold input stimulus sensed by a sensor.

[0086] In this example, pin 210 is a mode pin and is a dedicated input for controlling the mode of the first circuit 217. Pin 212 is a voltage drain (VDD) pin that inputs the VDD of the first circuit 217 to the switch 204. In this example, the device 219 (or the second circuit 218) controls the operating mode of the first circuit 217 by sending a mode signal that sets mode = 1 (i.e., mode = VDD) to the mode pin 210 (e.g., by routing VDD to the detection circuit 206 to transition the first circuit 217 to the wake-up sense input mode in which the detection circuit 206 is powered on). In this example, pin 210 includes a pad configured to receive a signal from an external processor that causes the first circuit 217 to switch from a first mode (e.g., wake-up sense input mode) to a second mode (e.g., operating mode). In this example, the first mode includes a mode in which the detection circuit 206 is substantially powered on. In this example, the second mode includes a mode in which the detection circuit 206 is substantially powered off. In this example, the first circuit 217 is configured to switch from the first mode to the second mode when an input is detected to meet one or more criteria.

[0087] In the case where the mode pin 210 (via the mode signal) is set to equal 0, the first circuit 217 operates in an operating mode (e.g., normal mode) in which the detection circuit 206 is powered off (or substantially powered off). That is, a voltage equal to VDD causes the detection circuit 206 to enter the wake-up sense input mode, while a floating signal or a low signal causes the detection circuit 206 to enter normal operation. The mode signal also configures an input bias circuit (e.g., bias circuit 218) to control switches (including those in the input bias circuit), which appropriately configures the input bias network and switches for the sensor 215.

[0088] In this example, the sensor 215 receives an input 215a, and the sensor 215 converts the input into an input voltage (VIN). The detection circuit 206 detects when the input meets one or more criteria. In this example, the detection circuit 206 is configured to operate at approximately 5 microamperes. For example, the detection circuit 206 detects when VIN is equal to a threshold voltage or reference voltage (VREF), such as VIN=VREF. When it is detected that one or more detection criteria are met, the detection circuit 206 generates a signal that causes the detection pin 209 to become "high" (e.g., having a value equal to 1). In this example, the detection pin 209 includes a pad that is configured to send a signal to the second circuit 218 that the input 215a of the specified sensor 215 meets at least one of the one or more detection criteria. There are various types of input stimuli including, for example, pressure and movement. An external processor or system (e.g., the second circuit 218) receives the signal from the detection pin 209. In response to the signal, the external processor is powered on or powered up to an increased power level (relative to the power level before the processor received the signal) or performs one or more specified actions (e.g., turning on a light). In addition, in response to the signal, the device 219 (or the second circuit 218 or even other circuits within the device 219) sets the mode pin 210 to a low value to cause the first circuit 217 to transition from the wake-up sensing input mode to the operating mode. In this example, the first circuit 217 is configured to receive a signal from a processor external to the first circuit 217 that is used to power off the detection circuit 206. In another example, the first circuit 217 is configured to receive a signal from a processor external to the first circuit 217 (e.g., the device 219) that is used to reduce the power level of the detection circuit 206 relative to the power level of the detection circuit 206 before the detection.

[0089] Once in operating mode, first circuit 217 processes input 215a and outputs VOUT (e.g., pin 213) to second circuit 218 in device 219 for application processing. In an example, second circuit 218 includes an external processor or subsystem. In this example, VOUT represents the output voltage based on the processing of input 215a. In a variation, pin 213 is optional (e.g., making VOUT optional).

[0090] refer to Figure 1 , the architecture diagram 300 shows the transducer and detection circuit 206. For the wake-up sound mode, the transducer 202 and the switch 204 ( )is biased (via biasing elements 310, 312) to the source voltage (VSS) of the circuit to which the device 200 is connected. Two PMOS source follower circuits 302, 304 are used to buffer the signal received from the transducer 202 and the VSS reference to the inputs of the differential preamplifier 306. The differential preamplifier 306 is biased to provide a gain of approximately 60 dBV to the signal from the transducer 202. The startup switch timing is configured by extending the reset time of the switch in the wake-up sound mode to stabilize the DC level of the source follower feeding the input to the differential preamplifier.

[0091] The output of the preamplifier 306 is routed to the input of the latch comparator 308, which is configured to determine whether the acoustic input meets one or more detection criteria. The reference side of the comparator is set to a voltage level scaled proportionally to the minimum acoustic detection threshold.

[0092] Once triggered (e.g., by detecting that the acoustic input meets one or more detection criteria), the latch comparator 308 latches the output to a high voltage level. This signal is further processed by the D-latch circuit 314, which acts as a one-time latch. The ASIC (e.g., IC 207) needs to be commanded by a mode signal to exit the wake-up sound mode to clear this signal. The latch signal DOUT is output from the ASIC for system processing.

[0093] Reference Figure 8A , the architecture diagram 320 shows the transducer 324 and the detection circuit 322. In the example, the detection circuit 322 is the same detection circuit as the detection circuit 206 in. For the wake-up sound mode, the transducer 324 and the switch 204 ( Figure 8A ) are biased (via biasing elements 326, 328) to the source voltage (VSS) of the circuit to which the device 200 is connected. Two PMOS source follower circuits 330, 332 are used to buffer the signal received from the transducer 324 and the VSS reference to the inputs of the AC coupling circuit 334 to allow the signal to be re-biased to a preferred common-mode voltage and increase (e.g., maximize) the dynamic range of the differential preamplifier 336. The differential preamplifier 336 is biased to provide a gain of approximately 60 dBV to the signal from the transducer 324.

[0094] The output of the preamplifier 336 is routed to the input of the differential comparator 338, which is configured to determine whether the acoustic input meets one or more detection criteria. The comparator 338 is designed to have hysteresis, and the hysteresis level collaborates with the gain of the differential preamplifier 336 to determine the detection criteria.

[0095] Once triggered (e.g., by detecting that an acoustic input meets one or more detection criteria), comparator 338 latches the output to a high voltage level. This signal is further processed by D-latch circuit 340, which acts as a one-time latch. The ASIC (e.g., IC 207 in

[0096] ) needs to be commanded by a mode signal to exit the wake-up sound mode to clear this signal. The latch signal DOUT is output from the ASIC for system processing.

[0097] The voltage level is set by the scaling factor of the MEMS, the attenuation of the source follower, and the gain of the differential preamplifier. a ) as follows:

[0098]

[0099] There is a trade-off between the various gain factors and the minimum detectable acoustic threshold. Increasing the gain of the preamplifier or the scaling factor of the MEMS will provide the ability to detect very quiet signals, however this needs to be balanced with the available margin due to VDD. If a louder acoustic signal is required to trigger the detection circuit, then gain needs to be removed from the circuit, or VREF increased.

[0100] Refer to Figure 5A , plot 400 shows the operating results of a device configured for sound wake-up. Representation 402 represents the signal (e.g., noisy ambient acoustic signal) that has been processed by the transducer and preamplifier. At 5 milliseconds, the transducer senses a 1 kHz acoustic stimulus, resulting in the waveform shown. In this example, representation 402 represents the acoustic stimulus. This acoustic stimulus processed by the transducer and preamplifier crosses the reference voltage line 404 slightly after 5 milliseconds.

[0101] Refer to , plot 450 shows the digital output signal over time as representation 452. In this example, the digital output is the digital output of the detection circuit that is processing the signal represented by 402. As shown in 450, for example, once the signal represented by 402 exceeds the reference voltage, the digital output transitions from low to high and remains high. The system (e.g., Figure 5B external processor 512 in The external processor 512) can then determine whether to return the microphone to the wake-up sound mode based on the result measurements of the surrounding acoustic environment during normal operation. For example, the system can monitor the acoustic signal (e.g., the voltage of the acoustic signal) and determine whether it will exceed the acoustic threshold in the wake-up sound mode. If the system does not measure an acoustic signal exceeding the threshold (e.g., an acoustic signal with a voltage exceeding the threshold voltage) within a certain period of time such as 5 minutes, the system can return the microphone to the wake-up sound mode.

[0102] In another example, the system can quickly restore the microphone to the WOS mode after exceeding the threshold and use other microphones to monitor the acoustic environment. The system can continuously reset the WOS microphone back to the WOS mode and wait until a certain period of time such as 5 minutes without exceeding the threshold. If the threshold is not exceeded within a certain period of time, the system can turn off the remaining microphones and enter the low-power state.

[0103] In an example, the acoustic threshold detection circuit appears in the system after the microphone (e.g., as Figure 8A shown). The circuit block will use the microphone output as its input, then can detect low-level signals, and provide commands to and control the output of the audio subsystem or the application processor.

[0104] In another example, instead of placing the detection circuit after the microphone, the detection is performed immediately after the transducer (e.g., by placing the detection circuit immediately after the transducer) to provide more refined system commands and control. For example, in the case where the microphone or the acoustic device is commanded to enter the wake-up sound mode, it only consumes 5 μA of current, reduced to 1 / 30 of the current consumption (150 μA) in normal mode operation, and provides a means to signal the system of an acoustic detection event and has the ability to have its mode controlled by the system. In this way, the entire audio subsystem can be powered off, saving a significant amount of power compared to other detection system architectures that require some audio subsystem or application processor to remain operational.

[0105] Based on the wake-up sound architecture, the overall power consumption of the system is reduced, and acoustic stimuli are provided to control the overall system state. Whether in the sleep mode or the active mode, the power consumption is almost zero. In the case of removing the direct implementation of the transducer, the overall sensitivity of the microphone is increased by nearly 60 dBV in this circuit. The sensitivity of the microphone is specified as -38 dBV for normal operation and industry standards. In the example of an acoustic stimulus of 1 Pa-RMS, the voltage output of the preamplifier is approximately 12.5 mV-RMS. When the wake-up sound mode is enabled, the sensitivity of the microphone is increased to nearly +20 dBV (i.e., for an acoustic stimulus of 1 Pa-RMS, the voltage output of the preamplifier is approximately 10 V-RMS). The voltage margin will ultimately limit the maximum acoustic stimulus that can be sensed before the electronic device saturates, but the working assumption is that the entire sound environment is quiet and full of low-level signals.

[0106] Referring to FIG. 8, a system architecture 500 is shown. In this example, the system 501 includes an acoustic device 504 and a processor 512 external to the acoustic device 504. In the example, the acoustic device 504 includes a device 200 having an acoustic transducer, a detection circuit, and a preamplifier ( )). The acoustic device 504 receives an acoustic input 502. In this example, the acoustic device 504 includes a sense pin 506 (e.g., which may be the same as sense pin 209), a mode pin 508 (e.g., which may be the same as mode pin 210), and an output voltage (VOUT) pin 510 (e.g., which may be the same as VOUT pin 211). The sense pin 506 is configured to indicate when the acoustic input 502 is equal to or exceeds a threshold voltage (e.g., VREF). The mode pin 508 is configured to indicate when the acoustic device 504 enters or exits the wake - up sound mode. The VOUT pin 510 specifies the output voltage (based on the acoustic input) from the acoustic transducer 504 for the processor 512 to process the acoustic input or audio input. Prior to the time of receiving the acoustic input, the acoustic device 504 is powered on, and the processor 512 is powered off or in a "watchdog" or polling state where the processor 512 intermittently polls the sense pin 506 for a signal. Additionally, at this time, the mode pin 508 is configured in the wake - up sound mode. When an acoustic input 502 greater than or equal to the threshold voltage is received, the sense pin 506 goes high (e.g., based on the output of a detection circuit in the acoustic device 504). The logic of the processor 512 in the watchdog state detects that the sense pin 506 has gone high. In response, the processor 512 powers on (e.g., the processor 512 is powered up) and sets the mode pin 508 to the normal mode, causing the acoustic device to transition out of the wake - up sound mode. By setting the mode pin 508 to the normal mode, the device 504 is instructed (by the processor 512) to power on a pre - amplifier (e.g., pre - amplifier 208 in FIG. 2) so that the acoustic device 504 can operate in the "normal mode" and power off the detection circuit of the acoustic device (e.g., detection circuit 206).

[0107] Reference Figure 5B , the mode diagram 550 shows the modes of the chip and how the chip enters these modes. Node 552 represents the state where the chip is off. Node 556 represents the state where the chip is operating in the working mode. In this example, when VDD has a voltage within a specified range (e.g., when VDD = 1.6V - 3.6V), the chip enters the working mode. When the mode is low or high impedance ("Hi - Z") (which indicates that the signal is "floating" or is driven by a powered - off electronic device), the chip remains in the working mode. When the mode goes high, the chip transitions from the working mode to the wake - up sound mode (represented by node 554). When VDD has a low voltage or VDD = 0V, the chip turns off.

[0108] [[ID=⑧]]Reference , another system architecture 600 is shown. In this example, system 605 includes an acoustic transducer 602 and a processor 608. Processor 608 includes an analog-to-digital converter (ADC) 604 and a threshold detector 606. In this example, threshold detector 606 is configured to detect when acoustic input 601 equals or exceeds a threshold level, for example, by detecting when the voltage generated by the acoustic input equals or exceeds a threshold voltage. For example, threshold detector 606 is a detection circuit (e.g., such as detection circuit 206( Figure 5A ))). However, in this example, detection circuit 606 is part of processor 608 and is not included in acoustic device 602. Because detection circuit 606 is part of processor 608 and is not included in acoustic device 602, processor 608 needs to remain powered on to detect audio stimuli.

[0109] In this example, ADC 604 and threshold detector 606 need to remain on from a time before acoustic input 601 is received. This is because acoustic device 602 does not include a detection pin (e.g., such as pin 506) to detect audio stimuli and send an indication of the detected signal to processor 608. (Again referring to , it is not an external processor, but acoustic device 504 that can perform this detection because the piezoelectric material in the transducer generates a voltage without the need for a voltage source). In this example, the detection is performed by processor 608 by converting VOUT 603 (based on the acoustic input) into digital data that can be processed by threshold detector 606, for example, by using ADC 604. Because the detection is performed by processor 608, logic (i.e., ADC 604) and threshold detector 606 need to remain on to detect acoustic stimuli. Thus, processor 608 (as Figure 5A the processor 512 in) can be in a polling state or cannot be powered down. Additionally, because acoustic device 602 does not include a mode pin, acoustic device 602 cannot be configured to switch between a mode where the detection device is powered on and another mode where the preamplifier is powered on. Instead, in acoustic device 602, the preamplifier must remain on and cannot be powered on or off via mode switching.

[0110] Refer to Figure 5C Figure 5A Figure 5A Figure 6A Figure 5A Figure 6B Figure 5A Figure 5A Figure 5A Figure 7A Figure 7B Figure 5A Figure 5A Figure 9 Figure 5A Figure 8B Figure 9 Figure 5A Figure 5A Figure 5A Figure 10, process 700 is implemented by a device (e.g., device 200 of FIG. 2 ) when implementing one or more techniques described herein. In operation, device 200 (and / or detection circuitry 206 in device 200) detects (702) when an acoustic input stimulus to acoustic transducer 202 of device 200 meets one or more detection criteria (e.g., retrieved by device 200 and / or programmed into device 200). Upon detection, detection circuitry 206 generates (704) a signal that adjusts the performance of device 200 by causing (706) circuitry (e.g., preamplifier 208) of device 200 to increase its power level relative to the power level of the circuitry prior to detection. As described herein, the generated signal causes preamplifier 208 to increase its power level by causing an external system to detect the signal and respond by instructing device 200 to enter an operational mode. In another example, the generated signal causes the preamplifier 208 to increase its power level by causing logic within the device 200 to receive and / or detect the signal and respond to instruct the device 200 to enter the operating mode. The device 200 processes (708) the acoustic input of the device 200 using the circuit with the increased power level.

[0111] In an example, a device (as described herein) operates in a low-power mode at the transducer level (if the device includes a transducer) and the sensor level (if the device includes a sensor). For example, the low-power mode includes a power consumption of less than 10 microamperes. In an example, the device includes: an acoustic transducer; and a first circuit configured to detect when a sound level within a frequency band (limited to) a frequency range exceeds a threshold level, or when an average sound level of multiple sound levels within the frequency band over a period of time exceeds a threshold level, and further configured to generate a first signal, for example, when the sound level or average sound level exceeds the threshold level. In this example, the acoustic transducer has a smooth response within the following speech frequency range, wherein the acoustic transducer is substantially equally sensitive to frequencies within the speech frequency range. In some examples, the threshold level is between 60 dB SPL and 90 dB SPL at frequencies within the frequency band. In other examples, the threshold level is between 40 dB SPL and 110 dB SPL at frequencies within the frequency band. In this example, the frequency range includes 300 Hz-5 kHz. That is, the first circuit is configured to process only those signals having levels within a specified range, which in this example is 300 Hz-5 kHz, but there may be other specified ranges. For those signals within 300 Hz-5 kHz, the first circuit is further configured to detect which of those signals exceeds a specified threshold (e.g., a predefined threshold). In this example, the first circuit is in a power mode that consumes less than 350 microwatts. In another example, the first circuit is in a power mode that consumes approximately 20 microwatts, consumes a range of approximately 20-350 microwatts, and so on. In other variations, the power mode that consumes less than 350 microwatts is a power mode that is less than 200 microwatts. The power mode that consumes less than 350 microwatts is a power mode that is less than 100 microwatts. The power mode that consumes less than 350 microwatts is a power mode that is less than 50 microwatts.

[0112] In some examples, the apparatus further includes a second circuit configured to generate a second signal based at least in part on a first signal of the first circuit. In this example, the band-divided sound level includes a limit of the sound level. The band-divided sound level is band-divided by the first circuit, or at the first circuit, where the band-division is completed inside the first circuit. In this example, the first circuit that performs band-division over the frequency range includes an acoustic transducer that performs band-division through the mechanical characteristics of the acoustic transducer, where the acoustic transducer mechanically has a resonant frequency of the acoustic transducer such that the acoustic transducer does not sense frequencies outside the frequency range because such external sensing exceeds the mechanical characteristics of the acoustic transducer. In this example, the holes in the diaphragm (of the acoustic transducer) itself perform band-division at low frequencies. In this example, there is no time for high-frequency equalization. Thus, the user will hear high-frequency sounds but not low-frequency sounds. That is, the first circuit is mechanically band-divided through the resonance of the apparatus. In another example, the first circuit is electrically band-divided rather than mechanically band-divided. In electrical band-division, the first circuit is restricted to the high-frequency side. The mechanism characteristics include mechanical or hardware capabilities. Band-division by the first circuit includes the first circuit being configured to detect only a specific acoustic range. The apparatus includes an encapsulation device that has an acoustic filter before the input port of the encapsulation device or the acoustic transducer to perform acoustic band-division on the first circuit.

[0113] In another example, the first circuit is configured to calculate an average sound level based on, for example, a plurality of sound levels that each occur within a specified amount of time or time period. In this example, the sound levels included in the average calculation are only those that occur within a specified frequency range such as 300 Hz - 5 kHz. Based on the calculated average value, the first circuit is configured to determine when the calculated average value exceeds a threshold. In variations of each of the foregoing examples (and more general examples described herein), the apparatus includes a sensor and the techniques described herein are directed to the sensor.

[0114] The apparatus further includes a second circuit configured to generate a second signal based at least in part on a first signal of the first circuit. In this example, the second circuit is further configured to send the second signal to a digital system to power on the digital system and perform digital signal processing (DSP). In another example, the second circuit is configured to send the second signal to another system to cause the other system to perform one or more actions in response to the second signal.

[0115] In an example, the device is a microphone and is included in other devices (e.g., a smart speaker device - a device that turns on when a user speaks to it). In this example, the microphone is on only when there is no user speaking to the smart speaker device, which results in a consumption of less than 10 microamps. Since the microphone is an analog device, the entire smart speaker device (e.g., when it is listening for sound / acoustic levels) operates as an analog device. In this mode, the first circuit is configured to detect only sound levels that exceed a specified threshold and occur within a specified range (e.g., rather than a specific word or keyword). Since the first circuit consumes less than 200 microwatts in this detection state, the smart speaker device can operate at a very low power. Since the first circuit only detects and evaluates frequencies or sound levels, and does not detect and evaluate words or other forms of utterances, the first circuit operates in this low-power state. In this low-power state, the smart speaker system does not need to run its digital system or components or its digital signal processing (DSP) system or components. Instead, the smart speaker system can operate entirely in analog mode. Then, once the first circuit detects that the acoustic level (or average acoustic level) exceeds the threshold, the first circuit generates a signal that causes the smart speaker device to power on its digital system and perform keyword detection, e.g., to detect whether the spoken word matches a keyword to "wake up" the smart speaker system. In some examples, the detection criteria (implemented by the first circuit for detection) specify that the input pressure stimulus of the sensor reaches the threshold input level a certain number of times. In this example, the threshold input level is the threshold acoustic input level. In other examples, the first circuit is configured to detect when the acoustic level of the acoustic transducer exceeds the threshold level a certain number of times. In other examples, the first circuit is configured to detect when the signal level of the sensor exceeds the threshold level a certain number of times.

[0116] Specifically, upon successful detection, the first circuit generates a first signal and sends the first signal to the second circuit. Then, the second circuit (based on the first signal) generates a second signal and sends the second signal to another system (performing DSP) within the smart speaker device. In this example, the first signal specifies whether the received audio input (or other input, e.g., pressure input, etc.) has exceeded the threshold. The second signal uses this information (specifying whether the threshold has been exceeded) to do something, e.g., by including an instruction to perform some action (e.g., turn on a light). In an example, the second circuit simply re-sends the first signal, for example, without generating a second signal. In this example, the acoustic transducer includes a piezoelectric acoustic transducer or a capacitive acoustic transducer. The first circuit includes an analog circuit, the second circuit includes an analog circuit, or both the first circuit and the second circuit each include an analog circuit. The device itself includes an analog device and / or a packaged device.

[0117] In another example, a device (including a first circuit and a second circuit) is attached to or near a physical device (e.g., such as a table). In this example, the device (e.g., in the case where the device includes sensors such as an accelerometer, a chemical sensor, an ultrasonic sensor, an acoustic piezoelectric transducer, a piezoelectric sensor, an acoustic transducer, an acoustic sensor, or a gyroscope) detects movement at the table. In this example, the device detects the movement via a first circuit (included in the device), the first circuit being configured to detect when an energy level (e.g., rather than a frequency level) that is band-divided over a frequency range exceeds a threshold level, or to detect when an average energy level of a plurality of energy levels each of which is band-divided over a frequency range within a certain period of time exceeds a threshold level, and the device is further configured to generate a first signal. In this example, the first circuit calculates the average energy level using the same technique as described above regarding calculating the average acoustic level. The device further includes a second circuit for generating a second signal based at least in part on the first signal of the first circuit. In this example, when the first circuit detects that the energy level (or the average energy level) exceeds a specified threshold, the first circuit sends a signal to the second circuit, and the second circuit in turn sends another signal (e.g., based on or the same as the signal received from the first circuit) to another device or an electronic system (e.g., a device for turning on a light). In this example, when the device (including the first circuit and the second circuit) detects movement at and / or near the table, the light is turned on. The device in this example includes and / or performs the above functions and features.

[0118] The implementation of the subject matter and the functional operations described in this specification can be implemented in digital electronic circuitry, in tangibly embodied computer software or firmware, in computer hardware including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. The implementation of the subject matter described in this specification can be implemented as one or more computer programs (i.e., one or more modules of computer program instructions encoded on a tangible program carrier for execution by, or to control the operation of, a processing device). Alternatively or additionally, the program instructions can be encoded on a propagated signal, which is an artificially generated signal, such as a machine-generated electrical, optical, or electromagnetic signal, generated to encode data for transmission to a suitable receiver device for execution by a processing device. A machine-readable medium can be a machine-readable storage device, a machine-readable hardware storage device, a machine-readable storage substrate, a random or serial access memory device, or a combination of one or more of them.

[0119] The term "processing device" includes various devices, apparatuses, and machines for processing data, including, for example, programmable processors, computers, or multiple processors or computers. The device may include dedicated logic circuits such as, for example, FPGAs (Field Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits). In addition to hardware, the device may also include code that creates an execution environment for the computer program being discussed, such as code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

[0120] A computer program (which may also be referred to as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages or declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program may correspond to a file in a file system, but it does not have to. The program can be stored in a part of a file that holds other programs or data (for example, one or more scripts in a markup language document), in a single file dedicated to the program being discussed, or in multiple cooperating files (for example, files that hold one or more modules, subroutines, or portions of code). A computer program can be deployed to execute on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communication network.

[0121] The processing and logical flows described in this specification can be performed by one or more programmable computers executing one or more computer programs to perform functions by operating on input data and generating output. The processing and logical flows can also be performed by dedicated logic circuits such as, for example, FPGAs (Field Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits), and the device can also be implemented as the dedicated logic circuit.

[0122] A computer suitable for executing a computer program includes, for example, a general-purpose microprocessor or a special-purpose microprocessor or both, or any other type of central processing unit. Generally, the central processing unit will receive instructions and data from a read-only memory or a random access memory or both. The basic elements of a computer are a central processing unit for performing or executing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include or be operably coupled to one or more mass storage devices such as, for example, magnetic disks, magneto-optical disks, or optical disks for storing data, to receive data from or transfer data to the mass storage device, or both. However, a computer need not have such devices. In addition, a computer may be embedded in another device (such as a mobile phone, a personal digital assistant (PDA), a mobile audio or video player, a game console, a global positioning system (GPS) receiver, or a portable storage device (such as, for example, a universal serial bus (USB) flash drive), etc.).

[0123] Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, for example: semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special logic circuitry.

[0124] Although this specification contains many specific implementation details, these should not be construed as limitations on any possible scope of claims, but rather as descriptions of features that may be specific to particular implementations. The specific features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, the various features described in the context of a single implementation may also be implemented separately or in any suitable sub-combination in multiple implementations. In addition, although the features may be described above as acting in a particular combination and even initially claimed as such, in some cases, one or more features from the claimed combination may be deleted from the combination, and the claimed combination may refer to a sub-combination or a variation of a sub-combination.

[0125] Similarly, although the operations are described in a particular order in the drawings, this should not be understood as requiring that the operations be performed in the particular order shown or in sequential order, or that all of the illustrated operations be performed, to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. In addition, the separation of the various system components in the above implementations should not be understood as required in all implementations, and it should be understood that the described program components and systems may generally be integrated in a single software product or packaged into multiple software products.

[0126] Particular implementations of the subject matter have been described. Other implementations are within the scope of the appended claims. For example, the actions recited in the claims can be performed in a different order and still achieve the desired results. As an example, the processes depicted in the accompanying figures do not necessarily require the particular order or sequence shown to achieve the desired results. In some implementations, multitasking and parallel processing may be advantageous.

Claims

1. A device for stimulus detection, comprising: A sensor; And An analog circuit configured to detect when an input stimulus to the sensor meets an adaptive threshold and further configured to generate a signal that causes a performance adjustment of the device when detected, wherein the adaptive threshold is a threshold that varies over time based on a detected change in the sound of the environment in which the device is located. The adaptive threshold is scaled based on the input stimulus and non-linearity such that in an environment with a poor signal-to-noise ratio, the magnitude of the adaptive threshold is independent of the waveform change indicating the sound level in the environment.

2. The device according to claim 1, wherein, The analog circuit is a first circuit, and wherein the device further comprises: A second circuit for processing the input after detection, wherein the second circuit is configured to increase the power level of the second circuit after detection relative to the power level of the second circuit before detection.

3. The device according to claim 1, wherein, The device is further configured to output data representing one or more sound levels before detecting an input stimulus that meets the adaptive threshold.

4. The apparatus according to claim 3, wherein, The output data represents multiple sound levels in frequency or time.

5. The device according to claim 1, further comprising: An amplifier circuit configured to track a sub-threshold sound signal, a threshold sound signal, and a supra-threshold sound signal in the environment of the device.

6. The apparatus according to claim 5, wherein, The amplifier circuit is further configured to sum the sub-threshold sound signal, the threshold sound signal, and the supra-threshold sound signal in the environment of the device.

7. The apparatus according to claim 6, wherein, The circuit comprises: An amplifier configured to apply a gain to the input stimulus to amplify the input stimulus, Wherein the gain is the sum of the sub-threshold sound signal, the threshold sound signal, and the supra-threshold sound signal in the environment of the device.

8. The device according to claim 1, further comprising: A bandpass filter bank including a plurality of filters to enable the adaptive threshold to be adaptive in different frequency bands.

9. The apparatus according to claim 1, wherein The circuit comprises: An RMS-to-DC converter configured to receive the input stimulus; and An amplifier configured to: receive the input stimulus from the RMS-to-DC converter and amplify the input signal according to the background sound level.

10. The device according to claim 1, wherein, The circuit is configured to detect sound signals in multiple frequency bands and is further configured to detect when the sound levels of at least a plurality of the sound signals in the multiple frequency bands increase or decrease relative to the sound levels of other sound signals detected at a previous time within a specified time period; Wherein the circuit is further configured to increase the value of the adaptive threshold when the sound levels of at least a plurality of the sound signals in the multiple frequency bands increase within the specified time period, wherein the increased value corresponds to the detected increase in the sound level; and Wherein, the circuit is further configured to reduce the value of the adaptive threshold when the sound levels of at least a plurality of the sound signals in the plurality of frequency bands are reduced within the specified time period, wherein the reduced value corresponds to the detected reduction in the sound levels.

11. The device according to claim 1, wherein, The adaptive threshold is a non-fixed threshold.

12. The device according to claim 1, wherein, The device is a microphone, an acoustic transducer or a MEMS piezoelectric transducer.

13. An adaptive acoustic detection circuit for detecting when an input stimulus of a sensor meets an adaptive threshold, the detection circuit comprising: A band-pass filter for receiving an output from the sensor; And An analog circuit fed with the band-pass filter output and configured to: detect when the output of the sensor meets the adaptive threshold and generate a signal that causes a performance adjustment of the device when detected, wherein the adaptive threshold changes over time according to a detected gradual change in the stimulus in the environment in which the device is located. Wherein the adaptive threshold is scaled according to the input stimulus and non-linearity such that in an environment with a poor signal-to-noise ratio, the magnitude of the adaptive threshold is independent of the waveform change indicating the sound level in the environment.

14. The adaptive acoustic detection circuit according to claim 13, wherein, The detection circuit further comprises: A converter circuit for converting the signal from the band-pass filter circuit into a DC signal; A fixed-gain amplifier for amplifying the DC signal; A threshold circuit for establishing a variable threshold level; and A comparator circuit having a first input fed with the amplified DC signal and a second input fed with the variable threshold level to generate a detection signal according to the value of the amplified DC signal relative to the value of the variable threshold level.

15. The adaptive acoustic detection circuit according to claim 14, wherein, The band-pass filter, the converter and the fixed-gain amplifier comprise a first channel of the detection circuit, and the detection circuit further comprises: At least one additional channel comprising a band-pass filter, a converter and a fixed-gain amplifier; and A summing amplifier for receiving the outputs from the first channel and the at least one additional channel to provide an output fed to the first input.

16. The adaptive acoustic detection circuit according to claim 15, wherein, The band-pass filters of the first channel and the at least one additional channel have passbands of different frequencies.

17. The adaptive acoustic detection circuit according to claim 13, wherein, The detection circuit further comprises: A variable-gain amplifier having an input for receiving an input signal, a control port and an output for providing an amplified output signal; A comparator circuit having a first input coupled to the output of the variable-gain amplifier and a second input fed with a fixed threshold level signal to generate a detection signal according to the value of the amplified output signal relative to the fixed value of the threshold level; and A feedback circuit for generating a control signal for controlling the gain of the variable-gain amplifier.

18. The adaptive acoustic detection circuit according to claim 17, wherein, The detection circuit further comprises: A high-pass filter and a low-pass filter serially coupled between the output of the variable-gain amplifier and the input of the comparator circuit.

19. The adaptive acoustic detection circuit according to claim 17, wherein, The feedback circuit comprises: A rectifier for converting the signal at the input of the comparator circuit into a DC signal; An analog-to-digital converter for converting the DC signal into a digital signal; and Control logic for receiving the digital signal and determining the value of the control signal fed to the control port of the variable gain amplifier.

20. The adaptive acoustic detection circuit according to claim 19, wherein, The feedback circuit includes: A low-pass filter coupled between the rectifier and the analog-to-digital converter.

21. A method for stimulus detection, comprising: Detecting when an input stimulus to a sensor of a device meets one or more detection criteria, wherein at least one of the one or more detection criteria includes an adaptive threshold that varies over time based on a detected change in the sound of the environment in which the device is located; Generating a signal upon detection that causes a performance adjustment of the device by increasing the power level of the device's circuitry relative to the power level of the circuitry before detection; and Processing the input of the device using the circuitry having the increased power level, wherein the adaptive threshold is scaled based on the input stimulus and non-linearity such that the magnitude of the adaptive threshold is independent of waveform variations indicating the sound level in the environment in an environment with a poor signal-to-noise ratio.

22. The method according to claim 21, comprising: Receiving data representing one or more sound levels in the environment in which the device is located; and Adjusting the adaptive threshold at least in part based on the one or more sound levels and data representing previously detected sound levels in the environment of the device.

23. The method according to claim 22, wherein, The one or more sound levels include an average sound level in the environment of the device over a specified amount of time.

24. The method according to claim 22, wherein, The one or more sound levels include a first sound level corresponding to a first frequency band and a second sound level corresponding to a second frequency band, the first frequency band and the second frequency band including different frequencies.

25. The method according to claim 22, comprising: Increasing the adaptive threshold when at least one of the one or more sound levels increases relative to a previously detected sound level in the environment of the device over a specified amount of time, wherein the increase in the adaptive threshold corresponds to the detected increase in at least one of the one or more sound levels.

26. The method according to claim 22, comprising: Decreasing the adaptive threshold when at least one of the one or more sound levels decreases relative to a previously detected sound level in the environment of the device over a specified amount of time, wherein the decrease in the adaptive threshold corresponds to the detected decrease in at least one of the one or more sound levels.

27. The method according to claim 22, wherein, Receiving data representing the one or more sound levels before detecting the input stimulus.

28. The method according to claim 21, wherein, The device includes a microphone, an acoustic transducer, or a MEMS piezoelectric transducer.

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