This invention is a system (100) and method for measurement of acoustic response, such as occurs in the ear canal when double evoked otoacoustic emission signals elicit an evoked response from the cochlea. A three sample stimulus includes a first signal, a time delayed second signal, and the useful superposition of the first and second signals. The time delay is less than the maximum latency of the cochlear emission. Each signal elicits a cochlear response that includes a linear response, which is eliminated by subtracting the first and second individual signal responses from the response to the useful superposition signal. One class of signals arises when the time delayed signal is a scaled version of the first signal. The signals may be presented using a single acoustic source (130) or separate acoustic sources (130, 132). Appropriate selection of time delays greatly reduces nonlinear response due to probe distortion. Using two acoustic sources (130, 132) probe distortion can be virtually eliminated. The invention also includes a noise coherence measurement to determine the relative levels of system response caused by random noise and nonlinear response. Real time artifact rejection techniques simplify data collection.
SYSTEM AND METHOD FOR ACOUSTIC RESPONSE MEASUREMENT IN THE EAR CANAL