Abstract: Driver circuitry is disclosed for driving an electroacoustic transducer to provide an output comprising both ultrasonic and audio signal components. The driver circuitry comprises an adjustment module configured to reduce the level of said ultrasonic component signal in response to an increase in an operational variable indicative of a level of said audio signal component, while also increasing the pulse duration, duty cycle, repetition frequency or frequency span or bandwidth of the ultrasonic component.

Abstract: A method in a biometric authentication system, generating an acoustic stimulus for application to a user’s ear; receiving an audio signal representing a response of the user’s ear canal to the acoustic stimulus; adapting an ear canal response estimate of the user’s ear canal to the acoustic stimulus to reduce an error between the audio signal and the ear canal response estimate; calculating one or more quality metrics, the quality metrics comprising one or more of: an ear canal response estimate quality metric comprising one or more energy characteristics of the ear canal response estimate; an error quality metric derived from the error; an audio response quality metric comprising one or more statistical characteristics of the audio signal; and determining a validity of the audio signal for use in a biometric process based on the quality metrics.

Abstract: Driver circuitry is disclosed for driving an electroacoustic transducer to provide an output comprising both ultrasonic and audio signal components. The driver circuitry comprises an adjustment module configured to reduce the level of said ultrasonic component signal in response to an increase in an operational variable indicative of a level of said audio signal component, while also increasing the pulse duration, duty cycle, repetition frequency or frequency span or bandwidth of the ultrasonic component.

Abstract: Driver circuitry is disclosed for driving an electroacoustic transducer to provide an output comprising both ultrasonic and audio signal components. The driver circuitry comprises an adjustment module configured to reduce the level of said ultrasonic component signal in response to an increase in an operational variable indicative of a level of said audio signal component, while also increasing the pulse duration, duty cycle, repetition frequency or frequency span or bandwidth of the ultrasonic component.

Abstract: A loudspeaker driver circuit, comprises: at least one input for receiving an input signal; a loudspeaker protection module coupled to the input for receiving the input signal and for generating a modified signal in response to the input signal; an amplifier coupled to receive the modified signal from the loudspeaker protection module and to generate an output signal; an output for outputting the output signal for driving a speaker; and an ultrasonic signal generator, for generating an ultrasonic signal, wherein the ultrasonic signal generator is coupled to the amplifier for applying the ultrasonic signal thereto.

Abstract: A loudspeaker driver circuit, comprises: at least one input for receiving an input signal; a loudspeaker protection module coupled to the input for receiving the input signal and for generating a modified signal in response to the input signal; an amplifier coupled to receive the modified signal from the loudspeaker protection module and to generate an output signal; an output for outputting the output signal for driving a speaker; and an ultrasonic signal generator, for generating an ultrasonic signal, wherein the ultrasonic signal generator is coupled to the amplifier for applying the ultrasonic signal thereto.

Abstract: Driver circuitry is disclosed for driving an electroacoustic transducer to provide an output comprising both ultrasonic and audio signal components. The driver circuitry comprises an adjustment module configured to reduce the level of said ultrasonic component signal in response to an increase in an operational variable indicative of a level of said audio signal component, while also increasing the pulse duration, duty cycle, repetition frequency or frequency span or bandwidth of the ultrasonic component.