In this video, Brian talks about the differences in the the THs in English. Some of the exercises he gives his students will help them both articulate and hear the differences. For example, students will practice both the voiced and voiceless THs together, one after the other: Th-Th-Th, etc. As well, he will get the students to practice tongue twisters that have certain combinations of sounds, such as S and TH: "Timothy Smith's teeth seem healthy", and for Z and the voiced TH: "Why's that?" and "He's that brother's though."