Otoacoustic emission acquisition using adaptive noise cancellation techniques

A Distortion Product Otoacoustic Emission (DPOAE) system utilizing multiple microphones and advanced noise cancellation methods is described. This application focuses on noise cancellation techniques used to reduce internal and external noise contamination especially at the frequencies under 1500 Hz. Two additional microphones were used to acquire external and internal noise reference signals from the non-test ear and from the testing environment. Hardware and software was developed and experiments conducted to test the feasibility of using two noise reduction techniques. Adaptive Noise Cancellation (ANC) and Adaptive Wiener Filtering (AWF). Data were acquired in single sweeps and processed off-line with each method. Additional real-time ANC experiments were also conducted. Experimental results demonstrated that the ANC algorithm has the ability to reduce background noise and improve the SNR levels of DPOAE signals by about 5 dB. The AWF algorithm was also found to improve SNR levels between 3 and 9 dB at the lower frequencies depending on the reference microphone combination