Adaptive analogue noise cancelling an evaluation tool

ams is a leading supplier of single chip solutions for active noise cancellation (ANC). These mixed signal ICs are mainly used for headphones and communication headsets. The current solution is using fixed analog filters to tune the circuit according to the acoustics of the headphone. The next generation of ANC chipsets should be adapted in such way, that it is possible to use it in applications where the acoustic situation is variable in a certain degree (e.g. different positions of a mobile phone in relation to the human ear). This can be done by retuning the analogue filters digitally in realtime. To determine the influence of variable acoustic situations on the performance of ANC chipsets an acoustic test stand consisting of a holding fixture for mobile phones and an Audio Precision Audioanalyzer controlled by a Labview application was built. By using the acoustic test stand it is possible to perform transfer function measurements as a function of the DUT0s position in relation to the artificial ear of a dummy head.