This invention relates to telephones with talker sidetone, an effect which occurs when a speaker hears a small amount of his own voice in the earpiece as a result of a proportion of the speech signal received by the microphone being fed back to the output signal supplied to the earpiece. This is a desirable feature in a telephone because it is interactive and gives the user a feeling that the telephone is "alive" and therefore functioning properly. A telephone without talker sidetone is disconcerting to use because it seems entirely passive to received speech and therefore "dead" to the user.
In conventional telephones the amplitude of the signal fed back as talker sidetone, the sidetone gain, is immutable. The gain level is preset to provide an appropriate level of talker sidetone for speech. A disadvantage of this is that any background noise that is present will also be picked up by the microphone and it too will be fed back to the earpiece. This is an undesirable effect which the present invention is intended to overcome.