My work focusses on the use of high frequency seismic waves to understand the detailed structure of Earth’s interior, throughout the core and mantle. While the rough velocity structure of the mantle is generally agreed upon, the smaller-scale structure is more enigmatic. By knowing the Earth’s structure across length-scales we can begin to understand the past and on-going physical processes. I employ arrays of seismometers to amplify small signals relative to the background noise, and to determine the incoming direction of seismic energy. Local arrays help me to enhance resolution of low-amplitude signals, allowing me to observe scattered seismic waves caused by kilometre-scale heterogeneities in the mantle. In addition, I use regional arrays to determine waveform variations caused by broader mantle and core structure.