Apparatus for testing hearing is arranged to deliver audio tones over the Internet to be output at a receiving station such as a users computer. The apparatus firstly constructs audio tones for transmission out of sets of components recorded at different modulation levels for each frequency. This allows significantly finer control over the sound level of the audio tones at the receiving station than would normally be available at the receiving end. Secondly, the apparatus supports a feedback loop, based on a calibrated audio tone delivered for output at the receiving station and transmitted as audible sound back to the hearing test apparatus via a voice activated modem, the apparatus sending display data to the receiving station representing the sound level of that audible sound such that a user can adjust one or more parameters of the receiving station so as to bring the sound level of the audible sound, indicated by the display data, to a calibrated level. Alternatively, the apparatus might adjust the parameters of the receiving station directly, using a Java applet or the like. Calibration can additionally or instead be provided by means of an audio pickup for measuring and feeding back the level of audio output at audio delivery equipment in use to deliver audio tones to a user.
