An apparatus, comprising: a flexible backing having an outer side and an inner side, and being configured for affixation to a side of a person's head with the inner side facing the person's head, wherein the flexible backing has a first arm with a length of at least 6 cm in a first direction and a second arm with a length of at least 6 cm in a second direction, the second direction enclosing an angle (Θ) between 65° and 115° with the first direction and the first and second arms (71, 72) being configured to enable the apparatus to be affixed next to an ear on the person's head; a first plurality of capacitively-coupled electrode elements positioned on the inner side of the flexible backing of the first arm, each of the first plurality of capacitively-coupled electrode elements having a conductive plate with a dielectric layer disposed thereon that faces inward; a second plurality of capacitively-coupled electrode elements positioned on the inner side of the flexible backing of the second arm, each of the second plurality of capacitively-coupled electrode elements having a conductive plate with a dielectric layer disposed thereon that faces inward; a first set of conductors that connects to the conductive plates of each of the first plurality of capacitively-coupled electrode elements; a second set of conductors that connects to the conductive plates of each of the second plurality of capacitively-coupled electrode elements; and a layer of adhesive positioned to hold portions of the flexible backing that are not covered by any of the electrode elements (81, 82) against the person's head. a flexible backing having an outer side and an inner side, and being configured for affixation to a side of a person's head with the inner side facing the person's head, wherein the flexible backing has a first arm with a length of at least 6 cm in a first direction and a second arm with a length of at least 6 cm in a second direction, the second direction enclosing an angle (Θ) between 65° and 115° with the first direction and the first and second arms (71, 72) being configured to enable the apparatus to be affixed next to an ear on the person's head; a first plurality of capacitively-coupled electrode elements positioned on the inner side of the flexible backing of the first arm, each of the first plurality of capacitively-coupled electrode elements having a conductive plate with a dielectric layer disposed thereon that faces inward; a second plurality of capacitively-coupled electrode elements positioned on the inner side of the flexible backing of the second arm, each of the second plurality of capacitively-coupled electrode elements having a conductive plate with a dielectric layer disposed thereon that faces inward; a first set of conductors that connects to the conductive plates of each of the first plurality of capacitively-coupled electrode elements; a second set of conductors that connects to the conductive plates of each of the second plurality of capacitively-coupled electrode elements; and a layer of adhesive positioned to hold portions of the flexible backing that are not covered by any of the electrode elements (81, 82) against the person's head.