1. A hearing test system comprising: an administrator device and a subject device connected via a data link; the administrator device comprising a user interface operable to enable selection of hearing test configuration parameters and a configuration engine operable to generate configuration signals for transmission to the subject device over the data link; the subject device comprising a user interface operable to detect user inputs, and a test engine operable to process the configuration signals in order to generate a series of stimulus trigger keys to drive the output of a series of audio test tones by local loudspeakers corresponding to the selected configuration parameters or to react a series of stimulus trigger keys driving the output of a series of audio test tones by external loudspeakers corresponding to the selected configuration parameters, the test engine further operable to record user inputs detected in response to said audio test tones for transmission to the administrator device via the data link, wherein the administrator device is further operable to output received details of the recorded user inputs via the user interface. A hearing test system as claimed in claim 1 wherein the user interface of the subject device comprises a touchscreen operable to detect user inputs in by detecting user touches of the touchscreen. A hearing test system as claimed in claim 2 wherein a user touch is detected as a touch event by the touchscreen and is determined to take place at a time coincident with the start of the touch event. A hearing test system as claimed in any preceding claim/ wherein if the test engine is operable to react to a received stimulus trigger key, the stimulus trigger key is generated by the administrator device or another device and the stimulus trigger key identifies the nature of the test tone. A hearing test system as claimed in any preceding claim wherein if the test engine is operable to generate a stimulus trigger key, the stimulus trigger key identifies the nature of the test tone to be output and the test tones are output by internal loudspeakers of the subject device or by external loudspeakers directly connected to and controlled by the subject device. A hearing test system as claimed in any preceding claim wherein the output sequence of test tones is determined randomly or pseudo randomly in response to configuration signal. A hearing test system as claimed in any preceding claim wherein the test engine is operable to determine whether a user input occurs during a reaction interval following the output of a test tone. A hearing test system as claimed in claim 7 wherein the test engine comprises a reaction switch operable in response to the output of a test tone or the generation or receipt of a stimulus trigger key to time the reaction interval. A hearing test system as claimed in any preceding claim wherein the test engine is operable to control the timing of test tone output. A hearing test system as claimed in claim 9 wherein the next test tone is output immediately following the end of the reaction interval. A hearing test system as claimed in claim 9 wherein the next test tone is output immediately following the end of a separation interval. A hearing test system as claimed in claim 10 wherein the separation interval commences: immediately following the output of a test tone; immediately following the end of the reaction interval; or immediately following detected user input. A hearing test system as claimed in claim 10 or claim 11 wherein the test engine comprises a separation switch operable in response to: the output of a test tone; the generation or receipt of a stimulus trigger key; or user input following a test tone to time the separation interval. A hearing test system as claimed in any preceding claim wherein the test engine is operable to generate and output animations related to the test via the subject device user interface. A hearing test system as claimed in claim 14 wherein if a user input is detected within the reaction interval, the test engine is operable to generate a positive animation for output via the user interface. A hearing test system as claimed in claim 14 or claim 15 wherein if a user input is detected outside the reaction interval, the test engine is operable to output a to generate a negative animation for output via the user interface. A hearing test system as claimed in any preceding claim wherein the test engine is operable to calibrate output sound levels of the internal loudspeaker. A hearing test system as claimed in claim 17 wherein calibration is achieved by determining the device type and looking up suitable calibration settings from a reference table. A hearing test system as claimed in any preceding claim wherein the subject device is operable to record ambient audio signals relating to the test environment in advance of a test and the test engine is operable to process the ambient audio signals to establish whether levels of ambient noise in the test environment are acceptable. A hearing test system as claimed in claim 19 wherein the test engine is operable to process the ambient signals by comparing the recorded ambient noise levels to one or more threshold levels A hearing test system as claimed in any preceding claim wherein the administrator device comprises a classification engine operable to process the received details of the recorded user inputs so as to classifying the test subjectâ s hearing on the basis of the recorded user inputs. A hearing test system as claimed in any preceding claim wherein the configuration engine is operable to vary any one or more of: tone frequency, tone volume, tone duration, reaction interval, separation interval, separation interval range. An administrator device suitable for configuring a subject device to carry out a hearing test, the test engine further operable to record user inputs detected in 21 response to said audio test tones for transmission to the administrator device via the data link, wherein the subject device is connected via a data link and comprises a user interface operable to detect user inputs, and a test engine operable to process the configuration signals in order to output a series of audio test tones corresponding to the selected configuration parameters or to react to a series of stimulus trigger keys driving the output of a series of audio test tones by external loudspeakers corresponding to the selected configuration parameters, the test engine further operable to record user inputs detected in response to said audio test tones for transmission to the administrator device via the data link, wherein the administrator device comprises: a user interface operable to enable selection of hearing test configuration parameters; and a configuration engine operable to generate configuration signals for transmission to the subject device over the data link, wherein the administrator device is further operable to output received details of the recorded user inputs via the user interface. A subject device suitable for carrying out a hearing test in response to configuration by an administration device connected via a data link, wherein the administrator device comprises a user interface operable to enable selection of hearing test configuration parameters and a configuration engine operable to generate configuration signals for transmission to the subject device over the data link, and wherein the administrator device is further operable to output received details of user inputs recoded by the subject device via the user interface; wherein the subject device comprises a user interface operable to detect user inputs; and a test engine operable to a test engine operable to process the configuration signals in order to output a series of audio test tones corresponding to the selected configuration parameters or to react to a series of stimulus trigger keys driving the output of a series of audio test tones by external loudspeakers corresponding to the selected configuration parameters, wherein the test engine is further operable to record user inputs detected in response to said audio test tones for transmission to the administrator device via the data link.
22 A method of testing a subjectâ s hearing comprising the steps of: configurating a subject device according to claim 24 using an administration device according to claim 23, providing the subject device to the test subject, outputting a series of audio test tones and related animations corresponding to the selected configuration parameters on the subject device; recording user inputs detected by the subject device in response to said audio test tones; transmitting the recorded user inputs the administrator device; and outputting received details of recorded user inputs on the administrator device.