An apparatus configured to be used in treating tinnitus, comprising a sound processing unit, an electrostimulation unit, and an interface therebetween, wherein: said electrostimulation unit comprises an array of electrocutaneous stimulators each of which can be independently actuated to apply a somatosensory stimulus to a subject, and an input for receiving a plurality of actuation signals from said interface and directing individual actuation signals to individual stimulators; and said sound processing unit comprises: an input configured to receive an audio signal; a digital signal processor operable to analyse said audio signal and generate said plurality of actuation signals representative of said audio signal by dividing said audio signal into a series of frames in the time domain, performing a transform on each frame to generate a set of coefficients representing said frame, and tonotopically mapping said set of coefficients to a set of actuation signals to be applied to the array said set of coefficients representing the signal in the frequency domain, and wherein the coefficients are mapped to the actuation signals such that coefficients representing similar frequencies are mapped to actuation signals directed to stimulators which are physically close to one another in said array; and an output configured to receive said plurality of actuation signals from said digital signal processor and to provide said plurality of actuation signals to said interface. said electrostimulation unit comprises an array of electrocutaneous stimulators each of which can be independently actuated to apply a somatosensory stimulus to a subject, and an input for receiving a plurality of actuation signals from said interface and directing individual actuation signals to individual stimulators; and said sound processing unit comprises: an input configured to receive an audio signal; a digital signal processor operable to analyse said audio signal and generate said plurality of actuation signals representative of said audio signal by dividing said audio signal into a series of frames in the time domain, performing a transform on each frame to generate a set of coefficients representing said frame, and tonotopically mapping said set of coefficients to a set of actuation signals to be applied to the array said set of coefficients representing the signal in the frequency domain, and wherein the coefficients are mapped to the actuation signals such that coefficients representing similar frequencies are mapped to actuation signals directed to stimulators which are physically close to one another in said array; and an output configured to receive said plurality of actuation signals from said digital signal processor and to provide said plurality of actuation signals to said interface. an input configured to receive an audio signal; a digital signal processor operable to analyse said audio signal and generate said plurality of actuation signals representative of said audio signal by dividing said audio signal into a series of frames in the time domain, performing a transform on each frame to generate a set of coefficients representing said frame, and tonotopically mapping said set of coefficients to a set of actuation signals to be applied to the array said set of coefficients representing the signal in the frequency domain, and wherein the coefficients are mapped to the actuation signals such that coefficients representing similar frequencies are mapped to actuation signals directed to stimulators which are physically close to one another in said array; and an output configured to receive said plurality of actuation signals from said digital signal processor and to provide said plurality of actuation signals to said interface.