Abstract: A wireless telephone communication device is operated in a hands-free mode with detected received audio being relayed for output on the speakers of a radio. A single two-frequency FM transmitter or a multi-frequency transmitter that transmits simultaneously on a plurality of channels relays the audio to the FM radio.

Abstract: A method and apparatus for reducing the echo in a hands-free digital cellular communications system is presented. Acting upon speech signals being present in the downlink, uplink speech frames generated by the hands-free communication device are attenuated to prevent the downlink speech signals from being transmitted at full volume back on the uplink as an echo. Added to the attenutated uplink speech frame is a noise frame generated by the hands-free communication device, which provides a consistent level of background noise to the person at the other end of the call. The noise codeword is further randomly ordered to prevent any modulative effects from the process.

Abstract: A telephone having a method and apparatus for increasing the intelligibility of the loudspeaker output and for echo cancellation. The telephone includes an intelligibility booster for processing a speech input signal to generate an intelligibility-enhanced signal. The intelligibility booster includes a reverberation signal path for generating a reverberation signal, a direct signal path for generating an attenuated direct signal corresponding to the input signal, and an adder for combining the reverberation signal and direct signal to generate the intelligibility-enhanced signal. The reverberation signal path includes an intelligibility-information emphasizer followed by a reverberation unit. In the preferred embodiment, the intelligibility information emphasizer is a high pass filter and/or compressor that generates an intelligibility-dense signal to generate the reverberation signal.

Abstract: In an audio system, a loudspeaker responds to an input signal producing a sound pressure wave having a linear component, which is linear function of the input signal, and an undesired non-linear component, which is a non-linear function of the input signal. Accordingly, it is desirable to reduce the non-linear component of the output sound pressure wave. An adaptive precompensating audio system for reducing this non-linear component includes a loudspeaker for producing a sound pressure wave and a precompensating filter for precompensating an input signal representative of the desired sound pressure wave. In addition, a microphone may be used to convert the resulting sound pressure wave into a sound signal and a precompensating filter modifier may be used to modify the precompensating filter in response to the sound signal. Preferably, the precompensating filter transforms the input signal using an inverse of an estimated transfer function for the loudspeaker.

Abstract: Selectively compressing the signal supplied to a loudspeaker based upon the volume setting for the sound level to be produced by the loudspeaker improves the intelligibility of human speech produced by a loudspeaker at high volume levels. Compression of the signal to the loudspeaker prevents the loudspeaker from overloading. The level of compression may be adjusted based upon the volume setting. The amplitude of an audio signal sent to a loudspeaker may be increased if below a preselected pivot point and increased if above the pivot point. The amount of increase or decrease in the amplitude may be proportional to the difference between the amplitude of the audio signal and the pivot point. This difference may also be raised to the power of a shape factor to determine the amount of increase or decrease in the amplitude of the audio signal.

Abstract: An echo-canceling system and method uses an echo estimate to modify the error signal which is obtained by the difference between an echo signal and the echo estimate. The modified error signal, rather than the error signal itself, is transmitted. By using the echo estimate as a parameter for modifying the error signal, improved hands-free performance may be obtained in a vehicular radiotelephone, such as a cellular telephone. Preferably, modification of the electrical error signal is performed by a center clipper which removes a portion of the electrical error signal which is below a variable threshold, wherein the variable threshold is determined by the echo estimate electrical signal. The variable threshold may be produced from the echo estimate electrical signal using an envelope detector.

Abstract: Selectively compressing the signal supplied to a loudspeaker based upon the volume setting for the sound level to be produced by the loudspeaker improves the intelligibility of human speech produced by a loudspeaker at high volume levels. Compression of the signal to the loudspeaker prevents the loudspeaker from overloading. The level of compression may be adjusted based upon the volume setting. The amplitude of an audio signal sent to a loudspeaker may be increased if below a preselected pivot point and increased if above the pivot point. The amount of increase or decrease in the amplitude may be proportional to the difference between the amplitude of the audio signal and the pivot point. This difference may also be raised to the power of a shape factor to determine the amount of increase or decrease in the amplitude of the audio signal.