Abstract: A noise cancellation system is provided, for generating a noise cancellation signal to be added to a wanted signal to mitigate the effects of ambient noise. The system comprises: an input, for receiving an input signal representing ambient noise; a detector, for detecting a magnitude of said input signal; and a voice activity detector, for determining voiceless periods when said input signal does not contain a signal representing a voice. The detector is adapted to detect the magnitude of said input signal during said voiceless periods, and the system is adapted to operate in a first mode when said input signal is above a threshold value, and a second mode when said input signal is below the threshold value. The first mode comprises generating a noise cancellation signal with a first magnitude for at least partially cancelling the ambient noise. The second mode comprises generating a noise cancellation signal with a second magnitude that is less than the first magnitude.

Abstract: A noise cancellation system is provided, for generating a noise cancellation signal to be added to a wanted signal to mitigate the effects of ambient noise. The system comprises: an input, for receiving an input signal representing ambient noise; a detector, for detecting a magnitude of said input signal; and a voice activity detector, for determining voiceless periods when said input signal does not contain a signal representing a voice. The detector is adapted to detect the magnitude of said input signal during said voiceless periods, and the system is adapted to operate in a first mode when said input signal is above a threshold value, and a second mode when said input signal is below the threshold value. The first mode comprises generating a noise cancellation signal with a first magnitude for at least partially cancelling the ambient noise. The second mode comprises generating a noise cancellation signal with a second magnitude that is less than the first magnitude.

Abstract: An adaptive, feed-forward, ambient noise-reduction system includes a reference microphone for generating first electrical signals representing incoming ambient noise, and a connection path including a circuit for inverting these signals and applying them to a loudspeaker directed into the ear of a user. The system also includes an error microphone for generating second electrical signals representative of sound (including that generated by the loudspeaker in response to the inverted first electrical signals) approaching the user's ear. An adaptive electronic filter is provided in the connection path, together with a controller for automatically adjusting one or more characteristics of the filter in response to the first and second electrical signals.

Abstract: A mobile electronic device is programmed so that when the device is running a an application and an event occurs that the device needs to notify the user about, then the device alters the visual and/or sonic behaviour of the application according to, a pre-defined event notification profile. The user can select a desired event notification profile from a menu of available profiles stored in the device. For example, the event notification profile could be graphics and/or audio in the application gently fading to an alternative state using a pre-defined transition effect.

Abstract: A method of estimating the carrier frequency of a phase-modulated signal involves a) extracting the pulse train from the signal, b) making an initial estimate of the carrier frequency, c) estimating the error in the initial estimate, d) using this error to generate a more accurate estimate of the carrier frequency, and repeating steps c) and d) until a sufficiently accurate estimate of the carrier frequency is obtained. Step c can involve extracting the phase information in the signal, mixing the signal down to 0 Hz by removing the initial estimate of the carrier frequency to give complex IQ data, calculating the phase of the signal as a function of time, calculating the mean phase, wrapping the data into a phase range equal to the size of the phase jump, and calculating the error in the initial estimate of the carrier frequency from the gradient of this graph.