a method of and apparatus for producing acoustic output employs a bending wave member to which a number of exciters are coupled over at least part of the area . the exciters are individually addressable to generate impulses in response to digital input that has been suitably shaped and delayed , the impulses being integrated in the panel so that a form of synchronous summation takes place by bending action making use of the dispersive properties of the device . the resulting acoustic output has a reinforced fundamental frequency and reduced harmonics .