A signal enhancer comprising: an input configured to receive an audio signal that has a wanted component and an unwanted component; a perception analyser configured to: split the audio signal into a plurality of spectral components; for each spectral component, designate that spectral component as belonging to the wanted component or the unwanted component in dependence on a power estimate associated with that spectral component; and if that spectral component is designated as belonging to the unwanted component, adjust its power by applying an adaptive gain to that spectral component, wherein the adaptive gain is selected in dependence on how perceptible the spectral component is expected to be to a user, characterized in that the perceptual analyser is configured to, for each spectral component that is designated as belonging to the unwanted component, compare its power estimate with a power threshold, and: if the power estimate is below the power threshold, select the adaptive gain to be a gain that will leave the power associated with that spectral component unchanged; and if the power estimate is above the power threshold, select the adaptive gain to be a gain that will reduce the power associated with that spectral component. an input configured to receive an audio signal that has a wanted component and an unwanted component; a perception analyser configured to: split the audio signal into a plurality of spectral components; for each spectral component, designate that spectral component as belonging to the wanted component or the unwanted component in dependence on a power estimate associated with that spectral component; and if that spectral component is designated as belonging to the unwanted component, adjust its power by applying an adaptive gain to that spectral component, wherein the adaptive gain is selected in dependence on how perceptible the spectral component is expected to be to a user, split the audio signal into a plurality of spectral components; for each spectral component, designate that spectral component as belonging to the wanted component or the unwanted component in dependence on a power estimate associated with that spectral component; and if that spectral component is designated as belonging to the unwanted component, adjust its power by applying an adaptive gain to that spectral component, wherein the adaptive gain is selected in dependence on how perceptible the spectral component is expected to be to a user, characterized in that the perceptual analyser is configured to, for each spectral component that is designated as belonging to the unwanted component, compare its power estimate with a power threshold, and: if the power estimate is below the power threshold, select the adaptive gain to be a gain that will leave the power associated with that spectral component unchanged; and if the power estimate is above the power threshold, select the adaptive gain to be a gain that will reduce the power associated with that spectral component. if the power estimate is below the power threshold, select the adaptive gain to be a gain that will leave the power associated with that spectral component unchanged; and if the power estimate is above the power threshold, select the adaptive gain to be a gain that will reduce the power associated with that spectral component.