Image of cremated whistle by Jorge Cervantes Martínez, lecturer-researcher at INAH (Instituto Nacional de Antropologia e Historia), published on mexicolore.co.uk.
If you would like more information on the Aztec "death whistle" but don't want to wade through a lot of terrible YouTube videos, check out the 2015 article by Roberto Velázquez Cabrera on Mexicolore and this 2008 article from the LA Times. Scroll to the bottom of the Mexicolore page to listen to a two second clip of one of the sounds these whistles were capable of making.