An acoustic touch apparatus, comprising: a substrate (51, 205) that has top (53, 210) and bottom surfaces (55, 215); a transmitting and receiving acoustic wave transducer pair (80a-80d), for each of the X and Y coordinates, on the top surface that is adapted to transmit and receive surface acoustic waves therebetween across a touch region on the top surface and to produce a touch response signal for a touch on the touch region; a transmitting and receiving acoustic wave transducer pair (180a-180d), for each of the X and Y coordinates, on the bottom surface that is adapted to transmit and receive surface acoustic waves therebetween, said substrate being adapted to propagate surface acoustic waves along each surface and to transfer, through the substrate via top-bottom oscillation, surface acoustic waves between the surfaces sufficient to enable a touch on the top surface to produce a touch response signal by the bottom surface transducer pair; and a controller that is adapted to operate on the touch response signals and non-touch response signals produced by each of the bottom surface transducer pair and the top surface transducer pair and determine positional information of a touch on the touch region from the response signals, wherein the controller operates on the response signals to determine the top and bottom touch sensitivity along an acoustic path across the touch region, and the top and bottom sensitivity is represented by the reduction in amplitude of the touch response signal to the non-touch response signal for each of the bottom surface transducer pair and the top surface transducer pair, characterized in that the controller determines the positional information of the touch by comparing the amplitude reductions of the touch response of the bottom surface transducer pair to the touch response of the top surface transducer pair, and the controller determines the positional information of the touch by applying the following relation: b(d)/t(d) = {b(L/2)/t(L/2)}·d·(L-d)/(L/2) 2, where L is the distance between the transducers in a respective transducer pair on the top and bottom surfaces; b(d) is the amplitude reduction of the touch response for a touch at distance d by the bottom surface transducer pair; and t(d) is the amplitude reduction of the touch response for a touch at distance d by the top surface transducer pair. a substrate (51, 205) that has top (53, 210) and bottom surfaces (55, 215); a transmitting and receiving acoustic wave transducer pair (80a-80d), for each of the X and Y coordinates, on the top surface that is adapted to transmit and receive surface acoustic waves therebetween across a touch region on the top surface and to produce a touch response signal for a touch on the touch region; a transmitting and receiving acoustic wave transducer pair (180a-180d), for each of the X and Y coordinates, on the bottom surface that is adapted to transmit and receive surface acoustic waves therebetween, said substrate being adapted to propagate surface acoustic waves along each surface and to transfer, through the substrate via top-bottom oscillation, surface acoustic waves between the surfaces sufficient to enable a touch on the top surface to produce a touch response signal by the bottom surface transducer pair; and a controller that is adapted to operate on the touch response signals and non-touch response signals produced by each of the bottom surface transducer pair and the top surface transducer pair and determine positional information of a touch on the touch region from the response signals, wherein the controller operates on the response signals to determine the top and bottom touch sensitivity along an acoustic path across the touch region, and the top and bottom sensitivity is represented by the reduction in amplitude of the touch response signal to the non-touch response signal for each of the bottom surface transducer pair and the top surface transducer pair, characterized in that the controller determines the positional information of the touch by comparing the amplitude reductions of the touch response of the bottom surface transducer pair to the touch response of the top surface transducer pair, and the controller determines the positional information of the touch by applying the following relation: b(d)/t(d) = {b(L/2)/t(L/2)}·d·(L-d)/(L/2) 2, where L is the distance between the transducers in a respective transducer pair on the top and bottom surfaces; b(d) is the amplitude reduction of the touch response for a touch at distance d by the bottom surface transducer pair; and t(d) is the amplitude reduction of the touch response for a touch at distance d by the top surface transducer pair.