Did you know your phone is a really good listener? Apps on your phone might be sending and receiving data over ultrasound. Ultrasonic communication is used for everything from tracking your daily habits to enabling light shows at music festivals. We hear from Yale Privacy Lab's Sean O’Brien and Michael Kwet, and privacy and technology counsel Katie McInnis. We also discuss the more positive uses of data over sound with LISNR CEO and co-founder Rodney Williams.​​​​​​​Twenty Thousand Hertz is produced out of the studios of Defacto Sound and hosted by Dallas Taylor.​​​​Go to forhims.com/20k for your $5 trial month.Consider supporting the show at donate.20k.orgEpisode transcript, music, and credits can be found here.