Abstract: A dynamically stabilizable amplifier drives an output current into an RLC load. A driver stage generates the output current, and a control circuit compares a current level of the amplifier output with a threshold and selectively enables a stabilizing resistor (to selectively shunt the load or dampen in series with the load, depending on RLC load type) at the driver stage output based on the comparison so that the amplifier is stable across a range of the output current level. The control circuit disables the resistor when the output current is above the highest threshold and enables it when below. The control circuit may control the resistor to have one of multiple resistance values based on a comparison with multiple thresholds. The output current level may be determined by replicating the output current level or by an input current level that sets the output current level independent of the load.

Abstract: A method for providing directed transmission of sound waves, through modulation on an ultrasonic carrier, may comprise connecting, at least one directed sound source to an audio system, emitting, via the at least one directed sound source, audio from the audio system, wherein the emitting comprises emitting medium frequency audio sound waves and higher frequency audio sound waves. The audio may be selected via a master control unit, which may be operatively coupled to a mobile application. In many embodiments, a first audio selection is configured to be heard only through a first directed sound source, and a second audio selection is configured to be heard only through a second directed sound source.

Abstract: A point-pressed audio pickup apparatus includes a deformation element and an audio pickup device. The deformation element is pushed by an external force to induce deformation, so that a distance sensing element in the audio pickup device can measure the deformation through the changed distance so as to trigger the audio pickup device to start receiving sound.

Abstract: A MEMS microphone includes a substrate defining a cavity including a first sidewall extending a vertical direction, a back plate disposed over the substrate and defining a plurality of acoustic holes, a diaphragm disposed between the substrate and the back plate, the diaphragm having at least one vent hole, an anchor extending from a circumference of the diaphragm to connect an end portion of the diaphragm to an upper surface of the substrate, and at least one path member communicating with the vent hole, the path member providing a flow path for the acoustic pressure to flow downwardly toward the cavity.

Abstract: A field programmable device or software-defined hardware can change its functions by using software codes to alter the routing path of interconnect signal lines or the electrical properties of fundamental building elements. The field programmable device includes I/O interface blocks and signal processing blocks comprising analog signal processing units, digital signal processing units, memory units, clock units, and other supporting functional units which are electrically connected by user programmable interconnect signal lines. The analog signal processing functions can be altered by changing the electrical properties of fundamental building elements as well as the programmable signal lines after the device is manufactured.

Abstract: A signal processing apparatus and a signal processing method are provided. In a case where an HS microphone detection circuit has just detected connection of a microphone contact point, an input and output IF blocks a sound signal which is input from the microphone contact point from a first input port of a sound processing apparatus for two seconds by an HS mute circuit. Thereby, it is possible to prevent an improper sound signal from the microphone contact point from being output from a left speaker and a right speaker of a headset through a right output port Rout and a left output port Lout of the sound processing apparatus. Therefore, it is possible to prevent unpleasant noise caused by the improper sound signal from being output to a user.

Abstract: Techniques for implementing an internal optical communication link in a power amplifier system are disclosed. In one embodiment, the techniques may be realized as a power amplifier system that includes a panel, an optical link, and a controller. The panel includes a plurality of signal endpoints and a first optical interface, the first optical interface being coupled to each of the plurality of signal endpoints. The optical link is coupled to the first optical interface. The controller is configured to manage operation of the power amplifier system and is coupled to the optical link via a second optical interface. The controller communicates with each of the plurality of signal endpoints over the optical link.

Abstract: Provided is a terminal device including: a communication unit that communicates with an audio reproduction device; a sound quality adjustment unit that performs sound quality adjustment on audio data; and a control unit that determines whether or not the audio reproduction device has a sound quality adjustment function depending on a communication result of communication based on a predetermined protocol, and turns on or off the sound quality adjustment function of the sound quality adjustment unit depending on a determination result.

Abstract: A signal amplifying circuit and associated methods and apparatuses, the circuit comprising: a signal path extending from an input terminal to an output terminal, a gain controller arranged to control the gain applied along the signal path in response to a control signal; an output stage within the signal path for generating the output signal, the output stage having a gain that is substantially independent of its supply voltage, and a variable voltage power supply comprising a charge pump for providing positive and negative output voltages, the charge pump comprising a network of switches that is operable in a number of different states and a controller for operating the switches in a sequence of the states so as to generate positive and negative output voltages together spanning a voltage approximately equal to the input voltage.

Abstract: An audio processing device includes: at least one processor configured to: generate a first signal by reducing components that fall below a first frequency in an audio signal; generate a second signal by reducing components that fall below a second frequency that is higher than the first frequency in the audio signal; select between a first state for outputting the first signal and a second state for outputting the second signal; and output one of the selected first or second signal as an output signal; and a class-D amplifier configured to amplify the output signal, in which, the at least one processor is further configured to: determine whether or not a power supply pumping phenomenon exists or a possibility of the power supply pumping phenomenon exists, in a power source that supplies a power supply voltage to the class-D amplifier; and in which, in the selecting between the first state and the second state, the at least one processor is configured to select: the first state in a case where a determination

Abstract: A system is provided to realize suppression by selecting wavelets for feature compression in distributed speech recognition. The system comprises a first device and a second device. The first device comprising: a first network module for connecting to a network; an acoustic transducer module for recording speech and outputting frames of recorded signal; and a first processor configured for the following: extracting multiple-dimensional speech features from the frames of the recorded signal to generate multiple feature sequences; applying discrete wavelet transform (DWT) to the feature sequences to obtain a plurality of component data; and transmitting at least one of the plurality of component data via the network, wherein another one of the plurality of component data is not transmitted.

Abstract: A method in a transducer assembly having an external-device interface coupled to a communication protocol interface of the transducer assembly. The transducer assembly is configured to convert an input signal having one physical form to an output signal having a different physical form. At least two electrical signals are received on corresponding contacts of the external-device interface of the transducer assembly. A characteristic of at least one of the electrical signals is determined by evaluating a logic transition of the signal. A unique identity assigned to the transducer assembly is determined based on the characteristic.

Abstract: An In-Building Communications system is disclosed which permits communication in tunnels, underground parking garages, tall buildings such as skyscrapers, buildings having thick walls of concrete or metal, and/or any building which has communication dead zones due to electromagnetic shielding. The invention includes a portable bi-directional amplifier (BDA) system, an outdoor antenna system attached to the building or independently mountable, an indoor antenna system attached to the building or independently mountable inside the building, and a standardized, In-Building Communications (IBC) interface box affixed preferably to the exterior of the building. The interface box communicates with antenna systems attached to the building.

Abstract: A signal modulator for modulating at least one input signal is disclosed. The modulator includes an adaptive ramp generator receiving a clock signal having a clock cycle. The adaptive ramp generator provides a ramp signal having a profile starting from a minimum level adjusted in each clock cycle. The signal modulator may receive a first, second, and third input signal, and a clock signal. The first and second input signals may derive from a single signal where the second signal is equal to the first signal shifted by 180 degrees. The third signal may be a fixed level that sets the nominal duty cycle of the modulator. The input signal having the highest amplitude among the first, second, and third input signals is identified. The minimum level of the ramp signal is adjusted, and the peak value of the ramp maintained substantially equal to the signal having the highest amplitude.

Abstract: Techniques for implementing an audio distribution system using only standard network cabling for both power transmission and audio signal transmission. The system comprising of one or more Audio-streaming Source Units and one or more self-contained Network-powered Speaker Units where a plurality of audio streams can exist simultaneously and any audio stream can be directed between any Audio-streaming Source Unit and any Network-powered Speaker Unit.

Abstract: An amplifier circuit for a parametric transducer, comprising: a signal processor for processing an input signal into first and second signals; and at least a pair of output stages arranged to respectively receive the first and second signals for generating amplified first and second signals respectively, which are provided to operate the parametric transducer. The input, first and second signals are arranged with a substantially similar frequency to cause a switching frequency of the amplifier circuit to be matched to a carrier frequency of the parametric transducer. A related audio device is also disclosed.

Abstract: Described herein is a head-mounted device including an audio system configured to provide a surround sound audio effect. The device may include one or more of a forehead assembly, a rear-head assembly, a set of speakers, a set of straps connecting the forehead assembly to the read-head assembly, and/or other components. The forehead assembly may include one or more speakers. Individual ones of the straps may include one or more speakers.

Abstract: A hearing assistance and/or noise suppression device leverages computing power of an external device with a digital signal processor, such as a special unit that is configured to communicate with a smart device (e.g., a smart phone, smart watch or smart pendant) or a smart phone with a digital signal processor. Methods include having a hearing transducer communicate with and offload computing tasks to an external device with a digital signal processor. Systems include a hearing transducer with transducer circuitry that receives, amplifies and outputs digital signal processed audio from another device. Methods provide self-adjustment and fitting through a touch screen interface, which can be conducted outside of a clinical setting in a real world environment, and method can include remote data collection and communications with clinicians.

Abstract: An In-Building Communications system is disclosed which permits communication in tunnels, underground parking garages, tall buildings such as skyscrapers, buildings having thick walls of concrete or metal, and/or any building which has communication dead zones due to electromagnetic shielding. The invention includes a portable bi-directional amplifier (BDA) system, an outdoor antenna system attached to the building or independently mountable, an indoor antenna system attached to the building or independently mountable inside the building, and a standardized, In-Building Communications (IBC) interface box affixed preferably to the exterior of the building. The interface box communicates with antenna systems attached to the building.

Abstract: The present invention provides an Effector Power Adapter for connecting an effector, the Effector Power Adapter includes a power supply module, at least one first voltage transformation module and multiple voltage output ports, wherein the voltage output port has at least one first voltage transformation output port. The first voltage transformation module is electrically connected to the power supply module and the first voltage transformation output port, and the first voltage transformation module controls the first voltage transformation output port to output numerically continuously adjustable voltages. The present invention further provides an Effector Working System, which has an effector and the above effector power adapter. The Effector Power Adapter and the Effector Working System provided by the present invention can apply different voltages to an effector to produce different sound effects, which enriches the playing effect and offers more musical creation space for music practitioners.

Abstract: An apparatus for a signal processor for Wide-Band Applications is provided. The signal processor includes a plurality of parallel branches. Each parallel branch includes a frequency shifter, a sigma-delta-modulator, and a filter. The output signal of each branch is combined via a signal recombiner. The signal processor is suitable for wide-band applications due to centering the zeros of the sigma-delta-modulator's noise transfer function and filter's noise transfer function at the frequency of the frequency shifter in the same branch of the signal processor. Centering these zeros at the frequency of the frequency shifter shapes the quantization noise added by the sigma-delta-modulator away from the input signal frequency to make it easier to remove the quantization noise. This wideband performance is also achieved due to the design of the embodiment's filters. The embodiments of this invention use filters with symmetric transition bands and a pass-band that is wide enough for use in wireless applications.

Abstract: A hybid resonant DC to DC converter uses an LLC or other resonant structure on the primary side, applying a two state waveform to one end of the resonant structure and a multi-state waveform to the other end of the resonant structure. The waveforms are at or near the resonant resonant frequency and the output voltage level is regulated by varying the shape of the multi-state waveform by varying the duty cycle of the switches used to generate it. The allows the converter to operate near or at its optimal resonant point, resulting in higher efficiency, over a wide range of regulated output voltage levels.

Abstract: A microphone circuit having an amplifier with an input operably coupled to a microphone motor also includes a low pass filter operably coupled to the output of the amplifier and a positive feedback network that operably couples to an output of the low-pass filter and to the amplifier input. For many useful application settings the aforementioned amplifier has unity gain while the positive feedback network has a fractional gain less than unity.

Abstract: An electronic device includes: first and second processing circuits; a current limiting circuit configured to limit the electric current supplied to the first processing circuit; and a power storage unit inserted between the current limiting circuit and the first processing circuit to be in parallel to the first processing circuit. The first processing circuit is supplemented with electric charge stored in the power storage unit in a case where an electric current exceeding a current limit value of the current limiting circuit is consumed. In response to the connection to an external power supply, a limit of inflow of the electric current to the first and second processing circuits is made and a charging mode is started, and then the limit is released and it is switched to an operating mode.

Abstract: A negative voltage circuit includes a dual charging circuit, a pumping capacitor circuit, a dual discharging circuit, an output switch circuit, and a load capacitor circuit. The dual charging circuit is configured to operate in a start-up or normal operating mode during a charging mode, and supply a first current in the start-up mode higher than a second current in the normal operating mode. The pumping capacitor circuit is configured to charge based on a charging current from the dual charging circuit. The dual discharging circuit is configured to operate in the start-up mode or the normal operating mode during a discharging mode, and discharge the pumping capacitor to allow a third current in the start-up mode to flow between the pumping capacitor and the terminal of the second operating voltage. The third current in the start-up mode is higher than a fourth current in the normal operating mode.

Abstract: Systems and methods for enhancing reverberated audio signals are disclosed. In one embodiment, a method is disclosed comprising receiving an audio signal; partitioning a frequency domain representation of the audio signal into a plurality of sub-band vectors; inputting each sub-band vector into a corresponding deep neural network; calculating, using the corresponding deep neural networks, a plurality of output vectors for each sub-band; concatenating the plurality of output vectors to generate a clean audio feature matrix; and converting the clean audio feature matrix into a time-domain audio signal.

Abstract: Disclosed herein is a device and method for intelligently reducing power consumption in an audio amplifier in the device, and in particular Class-D amplifiers, through the use of metadata associated with settings of the playback device and/or content to be played on the playback device. The device includes components for analyzing the settings and content metadata and regulates the voltage provided to the audio amplifier based on this analysis.

Abstract: Systems and methods are described for measuring capture performance of multiple voice signals. A first speech signal is applied to a device, and measured at far-end at a far-end of a testing environment. A second speech signal is separately applied to the device, and is also measured at the far end. The measured speech signals are added, and a quality assessment model is applied to the first far-end combined signal to obtain a first quality metric. The first speech signal and the second speech signal are then both applied at the same time to the device and measured at the far-end. The quality assessment model is applied to the second far-end combined signal to obtain a second quality metric. The quality metric for the second far-end combined signal is normalized, based on the first quality metric, to obtain a performance index for the device.

Abstract: Provided are systems and methods for utilizing digital microphones in low power keyword detection and noise suppression. An example method includes receiving a first acoustic signal representing at least one sound captured by a digital microphone. The first acoustic signal includes buffered data transmitted with a first clock frequency. The digital microphone may provide voice activity detection. The example method also includes receiving at least one second acoustic signal representing the at least one sound captured by a second microphone, the at least one second acoustic signal including real-time data. The first and second acoustic signals are provided to an audio processing system which may include noise suppression and keyword detection. The buffered portion may be sent with a higher, second clock frequency to eliminate a delay of the first acoustic signal from the second acoustic signal. Providing the signals may also include delaying the second acoustic signal.

Abstract: A method and operates for generating a boost control signal for a DC-DC-booster is described. An audio signal may be received comprising a plurality of audio sample values. The audio signal may be delayed for a delay time. A maximum-delayed-value of the audio sample values during the delay time may be determined. The boost control signal may be generated from the maximum of the non-delayed audio signal sample value and the maximum-delayed-value.

Abstract: A load detector for an audio system comprising a closed-loop amplifier is described. The load detector includes a noise detector configured to be coupled to the output of the closed-loop amplifier. The noise detector detects a noise signal at least partially generated by the amplifier. The generated noise signal comprises frequencies outside the audible frequency range due to the noise shaping of the amplifier. The load detector further includes a parameter calculation module having an input coupled to the output of the noise detector and an output. The parameter calculation module is configured to determine a parameter value relating to an impedance of the amplifier output load from the detected noise signal and to output a load detection signal dependent on the determined parameter value. The load detector may detect the presence of a load such as a tweeter without generating a reference signal.

Abstract: An In-Building Communications system is disclosed which permits communication in tunnels, underground parking garages, tall buildings such as skyscrapers, buildings having thick walls of concrete or metal, and/or any building which has communication dead zones due to electromagnetic shielding. The invention includes a portable bi-directional amplifier (BDA) system, an outdoor antenna system attached to the building or independently mountable, an indoor antenna system attached to the building or independently mountable inside the building, and a standardized, In-Building Communications (IBC) interface box affixed preferably to the exterior of the building. The interface box communicates with antenna systems attached to the building.

Abstract: A duty-cycled acoustic sensor saves power, for example, by operating for relatively short periods of time in a repetitive manner. A sensor bias current provides operating power to the sensor. An output analog signal from the sensor carries the information induced by the sensor upon the bias signal. Capacitive coupling is employed to remove direct DC voltage from the output analog signal to generate an analog input signal for acoustic analysis. A capacitor for capacitive coupling is pre-charged to reduce the charging time of the capacitor as the sensor is being powered up. After the capacitor is sufficiently precharged, acoustic analysis is performed on the analog input signal. The sensor is powered down by substantially blocking current flow through the sensor, which saves power. Results of the acoustic analysis can be used, for example, to control parameters of the duty-cycling of the acoustic sensor.

Abstract: The electronic circuit having an input stage for pre-amplifying an electrical input signal of the electronic circuit provided by a transducer. The electronic circuit has an output stage for providing a microphone output signal by processing an output signal of the input stage. The electronic circuit has an adjustable output load arranged and configured for setting a current draw of the output stage. Additionally, the electronic circuit has a measurement circuit configured to capture the output signal of the input stage and an automatic control circuit configured to adjust the adjustable output load dependent on the captured output signal of the input stage.

Abstract: In general, according to one embodiment, an ultrasonic diagnostic apparatus includes an ultrasonic probe, a plurality of power supplies implemented by circuitry, at least one pulser, and a controller implemented by circuitry. The ultrasonic probe includes a plurality of piezoelectric transducers which generate ultrasonic waves in response to supplied driving signals. The pulser outputs the driving signal based on an applied voltage applied from any one of the plurality of power supplies. The controller switches the plurality of power supplies in accordance with the at least one pulser used for generation of the driving signal in one transmission mode period.

Abstract: A circuit for biasing a transducer including a first plate and a second plate includes a front-end buffer and a charge pump. The front-end buffer generates an internal signal at an internal node in response to a voltage signal of the second plate. The transducer receives the incident sound wave at the first plate to generate the voltage signal at the second plate. The charge pump boosts the internal signal into a boost voltage at the first plate according to a first clock signal.

Abstract: An amplifier circuit includes an amplifier and a voltage boost circuit configured to provide a variable supply voltage to the amplifier, the variable supply voltage continuously proportional to an audio input signal, the variable supply voltage configured to follow an output of the amplifier.

Abstract: In general, the subject matter described in this disclosure can be embodied in methods, systems, and program products for analyzing, by a computing system, one or more signals transmitted to an audio transducer. The computing system determines, based on the analyzing the one or more signals, an inductance of electronic components affecting the one or more signals. The computing system modifies, based on using the determined inductance to determine that atypical displacement of the membrane of the audio transducer has occurred, the one or more signals to compensate for the atypical displacement of the membrane of the audio transducer.

Abstract: An embodiment amplifier circuit includes a pair of subcircuits that includes a first subcircuit and a second subcircuit, each of which includes a buffer amplifier and a feedback circuit that includes a feedback capacitor. The amplifier circuit also includes a pair of output terminals. The first subcircuit and the second subcircuit each generate a different output signal of a pair of output signals that includes a first output signal and a second output signal. The amplifier circuit is configured for receiving a positive differential input signal at the first subcircuit, receiving a negative differential input signal at the second subcircuit, and receiving the pair of output signals at the pair of output terminals. The amplifier circuit is also configured for transmitting the first output signal to the feedback circuit of the first subcircuit, and transmitting the second output signal to the feedback circuit of the second subcircuit.

Abstract: A computer-implemented method to generate an audio output signal is disclosed. The method may include receiving an audio input signal at an automatic gain control (AGC) unit. The method may further include receiving a volume setting indicator signal at the AGC unit. Further, the method may include setting one or more operational parameters for the AGC unit based on the volume setting indicator signal. In addition, the method may include applying a gain to the audio input signal based on the one or more operational parameters to generate an audio output signal at a desired output level.

Abstract: A flat panel speaker system is provided. The system includes, a modified panel having a front surface and a rear surface, wherein the modified panel acts as a diaphragm for the flat panel speaker system; a supporting member coupled to the rear surface of the modified panel; and a detachable driver operationally coupled to the supporting member.

Abstract: An audio system includes a reference voltage generation circuit to generate a digital encoding signal and generate an analog reference voltage according to the digital encoding signal, wherein, during a booting procedure and/or a shutdown procedure, the analog reference voltage is smoothly increased and/or decreased at a smooth rate related to a bit number of the digital encoding signal; a first analog operational amplifier for receiving the analog reference voltage to generate a common voltage, which is smoothly increased and/or decreased during the booting procedure and/or the shutdown procedure; and a differential analog operational amplifier pair, coupled to the first analog operational amplifier, for receiving a differential audio input signal pair and outputting a differential output voltage pair to drive a load, wherein, during the booting procedure and/or the shutdown procedure, the differential audio output signal pair is smoothly increased and/or decreased.

Abstract: Described herein is a head-mounted device including an audio system configured to provide a surround sound audio effect. The device may include one or more of a forehead assembly, a rear-head assembly, a set of speakers, a set of straps connecting the forehead assembly to the read-head assembly, and/or other components. The forehead assembly may include one or more speakers. Individual ones of the straps may include one or more speakers.

Abstract: This application relates to an integrated circuit die (200) comprising a MEMS transducer structure (101) integrated with associated electronic circuitry (102). The electronic circuitry comprises a plurality of transistors and associated interconnections and is formed in a first area (103) of the die from a first plurality (104) of layers, e.g. formed by CMOS metal (107) and dielectric (108) layers and possibly doped areas (106) of substrate (105). The MEMS transducer structure is formed in a second area (111) of the die and is formed, at least partly, from a second plurality (112) of layers which are separate to the first plurality of layers. At least one filter circuit (201) is formed from said second plurality of layers overlying the plurality of transistors of the electronic circuitry (102).

Abstract: A powered speaker system comprising a cabinet and an input to receive an audio signal from an external amplifier. An audio splitter receives and splits the audio signal into first and second portions. At least one first speaker driver receives the first portion of the split audio signal, and an effects output jack receives the second portion. An effects input jack that is connectable to the external effects device, receives the second portion of signal that is modified by the external effects device. An internal amplifier is coupled to the effects input jack and receives and amplifies the modified second portion of the signal. At least one second speaker driver receives from the internal amplifier, the amplified modified second portion. The first speaker driver outputs the first portion simultaneously while the second speaker driver outputs the amplified modified second portion of the split audio signal.

Abstract: A sound detection system of a musical instrument with vibrating parts includes at least a pair of sensors and a preamplification unit for processing the signal output from the two sensors along respective channels. At least one of the pair of sensors is a piezoelectric transducer and the other one of the pair of sensors is a different-type transducer. The preamplification unit includes, for each channel, an input stage, including an amplifier circuit and an equalization circuit, and an output stage including at least a weighted adder circuit and at least two volume controls with arbitrary logarithmic response curve. At least the input stage for the channel of the piezoelectric transducer is a charge amplifier circuit and at least one of the other input stages can be configured both as a charge amplifier and as non-inverting amplifier with high input impedance. The equalization circuit includes an RC circuit.

Abstract: An audio amplifier has an input for an audio signal being amplified and an output powering a load on the basis of the amplified audio signal; a generator of reference voltage of very high linearity and low output impedance, able to receive, as input, the audio signal to be amplified; a power current generator including a power voltage generator whose output is connected to the output of the reference voltage generator through a coupling inductance; and a signal adder introducing, for its control, as input to the power current generator, a signal representative of the current provided as output by the reference voltage generator. The signal adder is able to introduce a signal ( L ? di LOAD dt ) representative of the product of the value of the coupling inductance and the drift with respect to time of the current ( di LOAD dt ) provided to the load.

Abstract: Aspects of the disclosure provide an apparatus having a first connector and a signal processing circuit. The first connector is configured to receive a second connector so that connecting terminals at respective portions of the first and second connectors are coupled together. The signal processing circuit is configured to generate a first output signal at a first amplification gain, determine a first load resistance value at a first connecting terminal of the second connector that is configured to receive the first output signal when coupled to the first connector, and set the first amplification gain based on the first load resistance value.

Abstract: An electronic device having a speaker device. The electronic device may include a housing, a speaker device disposed inside the housing, and a sound generation circuit electrically connected to the speaker device. The speaker device may include a sound generation plate movable in a first direction, and a sound reflection construction facing the sound generation plate to form a space between the sound generation plate and the sound reflection construction. The sound generation plate includes a first surface disposed substantially at a center of the sound generation plate, the first surface having a convex shape when viewed from inside the space, and the sound reflection construction includes a second surface substantially aligned with the first surface along an axis of the housing, the second surface having a concave shape when viewed from inside the space.

Abstract: The DC detection circuit includes: a OR circuit configured to generate a logical OR flag on the basis of logical OR of values of X bits from a (MSB-1)th bit to a (MSB-X)th bit of input data; a NAND circuit configured to generate a NAND flag on the basis of a NAND of values of X bits from the (MSB-1)th bit to the (MSB-X)th bit of the input data; a counter configured to count up and a counter value which outputs a DC detection flag if a counter value is exceeds predetermined set value on the basis of the MSB and any one of the logical OR flags of NAND flags. Accordingly, safety can be secured by detecting whether the DC data is included in the input PCM data, and thereby preventing degradation and breakage of the loudspeaker etc. due to the DC data.