The Effect of Calibration Errors When Combining Sound Field Interpolation with Head-Related Transfer Functions

In this work, we study the problem of estimating the in-ear sound field using microphone measurements at nearby positions. Typically, the sound field is first interpolated to the position of the head under free-field assumptions, followed by filtering through pre-measured head-related transfer functions (HRTFs). While properties of free-field interpolation methods have been well studied with respect to calibration errors, less is known about these properties when used in combination with a head-related transfer function. Herein, these properties are evaluated through controlled experiments in an anechoic chamber. The results indicate that, in the presence of errors in the assumed temperature and diffuseness of the sound field, it is always beneficial to use HRTFs on top of free-field interpolation for interpolating the in-ear sound field. However, interestingly, for large errors in the assumed orientation of the head, the use of an HRTF can even produce worse interpolation as compared to free-field interpolation.