To elaborate, to create the sound files, I used Bethesda Archive Extractor to access the original files, Unfuzer to convert the extracted .fuz files to .wav files, Audacity to splice the .wav files, and Unfuzer again to convert the new .wav files to .fuz files. I then placed them in the directory \Fallout 4\Data\Sound\Voice\Fallout4.esm\RobotMrHandy\. (Note that the \Fallout4.esm\ directory is NOT actually a .esm file, but instead a normal folder.)