A method of calibrating an earphone may include: securing an ANC earphone to a calibration fixture, the calibration fixture including an ear model configured to support the ANC earphone, the ear model having an ear canal configured to anatomically resemble a human ear canal and a concha configured to anatomically resemble a human ear concha, the ear canal extending from the concha to an inner end of the ear canal; generating, with the ANC earphone, an audio signal based on a reference tone; determining a characteristic of the audio signal; comparing the characteristic of the audio signal to a previously determined reference characteristic; and adjusting a gain value of the ANC earphone based on the comparing. Additional methods and apparatus are also disclosed.

Active noise reduction (ANR) headphones and associated methods are provided. The ANR headphones may include a memory to store a plurality of profiles each including controller information and acoustic parameters in addition to a profile selection routine executable by a processor of the ANR headphone. The profile selection routine may be configured to identify acoustic characteristics of a subject wearing the ANR headphone, compare the acoustic characteristics of the subject with the acoustic parameters of the plurality of profiles, select a profile from the plurality of profiles based on the comparison between the acoustic characteristics of the subject with the acoustic parameters of the selected profile, and provide the controller information of the selected profile to a noise reduction circuit of the ANR headphone.

A method of operating an audio system in a vehicle includes providing m number of microphones disposed within a passenger compartment of the vehicle. The microphones produce a plurality of microphone signals. Within the passenger compartment of the vehicle, k number of loudspeakers are provided. A plurality of convergence factors for use in performing active noise control are estimated. The estimating includes calculating an Eigen value () of an autocorrelation matrix of a passenger compartment transfer function as

[00001]${}_k\left(\right)=\frac{{A_k\left(\right)}^2}{2},$

wherein A.sub.k() is the frequency response of the passenger compartment transfer function. A frequency .sub.min of a local minimum of () is determined. A largest stable value for Max(.sub.min) is found by experimentation, wherein a rotational speed of an engine of the vehicle, expressed in revolutions per minute, f.sub.rpm=2.sub.min. A calibration factor is calculated as L=(.sub.min)Max(.sub.min). All values of Max() are estimated as

[00002]$\mathrm{Max}\left(\right)=\frac{L}{\left(\right)}.$

A plurality of active noise controlled audio signals are transmitted to the loudspeaker. The active noise controlled audio signals are dependent upon the microphone signals and the estimated convergence factors.

A method for determining an estimation of a secondary path transfer characteristic in an ANC system is described herein. In accordance with one example of the invention, the method includes the positioning of a microphone array in a listening room symmetrically with respect to a desired listening position and reproducing at least one test signal using a loudspeaker arranged within the listening room to generate an acoustic signal. The acoustic signal is measured with the microphones of the microphone array to obtain a microphone signal from each microphone of the microphone array, and a numerical representation of the secondary path transfer characteristic is calculated for each microphone signal based on the test signal and the respective microphone signal. The method further includes averaging the calculated numerical representations of the secondary path transfer characteristic to obtain the estimation of the secondary path transfer characteristic to be used in the ANC system.

A personal audio device, such as a wireless telephone, includes an adaptive noise canceling (ANC) circuit that adaptively generates an anti-noise signal from a reference microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. An error microphone is also provided proximate the speaker to measure the ambient sounds and transducer output near the transducer, thus providing an indication of the effectiveness of the noise canceling. A processing circuit uses the reference and/or error microphone, optionally along with a microphone provided for capturing near-end speech, to determine whether the ANC circuit is incorrectly adapting or may incorrectly adapt to the instant acoustic environment and/or whether the anti-noise signal may be incorrect and/or disruptive and then take action in the processing circuit to prevent or remedy such conditions.

A method of calibrating an earphone may include: securing an ANC earphone to a calibration fixture, the calibration fixture including an ear model configured to support the ANC earphone, the ear model having an ear canal configured to anatomically resemble a human ear canal and a concha configured to anatomically resemble a human ear concha, the ear canal extending from the concha to an inner end of the ear canal; generating, with the ANC earphone, an audio signal based on a reference tone; determining a characteristic of the audio signal; comparing the characteristic of the audio signal to a previously determined reference characteristic; and adjusting a gain value of the ANC earphone based on the comparing. Additional methods and apparatus are also disclosed.

Ambient sound is converted into digital signals. A processor performs active noise cancellation and/or a transformation operation that is distinct from the active noise cancellation on the digital signals. The active noise cancellation and the transformation operation transform the digital signals into modified digital signals. The modified digital signals are converted into modified analog signals. The modified analog signals are outputted as audio waves. An interior microphone is configured to output an output signal to the processor in response to receiving the modified analog signals. In response to receiving the output signal from the interior microphone, the processor is configured to determine whether the modified digital signals produce desired audio waves.

A system and method for estimating secondary path impulse response (IR) for an active noise cancellation (ANC) system to enhance performance of the ANC system in a near-imperceptible manner is provided. An adaptive music interference canceller (AMIC) uses music signals as test signals and ANC error microphones to estimate the secondary path IR between all speakers and microphones. The system validates that the music signals have sufficient audio content to be considered an adequate test signal. Furthermore, the system employs additional signal processing to ensure that a unique IR for all speakers and microphones can be obtained using the audio test signals. New coefficients of the AMIC filter are calculated, in real time, using the music signals and can be copied into the estimated secondary path for the ANC system. A supervisor unit manages enabling and disabling the AMIC as needed for calculating and copying coefficients.

An earpiece for real-time audio processing of ambient sound includes an ear bud that provides passive noise attenuation to the earpiece such that exterior ambient sound is substantially reduced within an ear of a wearer, an exterior microphone that receives ambient sound and converts the received ambient sound into analog electrical signals, and an analog-to-digital converter that converts the analog electrical signals into digital signals representative of the ambient sounds. The earpiece further includes a digital signal processor that performs a transformation operation on the digital signals according to instructions received from a mobile device, the transformation operation transforms the digital signals into modified digital signals, a digital-to-analog converter that converts the modified digital signals into modified analog electrical signals, and a speaker that outputs the modified analog electrical signals as audio waves.

A method for playback of an audio signal at an individual seat-based sound (ISS) system in a coherent listening environment having a plurality of ISS systems and a plurality of listening modes. Each ISS system has a single transducer. A listening mode and a set of playback preferences are selected. A crosstalk cancellation algorithm for the ISS system of interest is generated using impulse response measurements of the audio signal, taken only in an acoustical domain, of a transfer function between the audio signal directly after the single transducer in the ISS system of interest and the audio signal at the head of the listener in the ISS system of interest. The crosstalk cancellation algorithm for the selected listening mode is applied to the audio signal, and the audio signal is played back at the single transducer of the ISS system of interest.