The High Altitude Student Payload (HASP) is a high altitude balloon system

designed to carry up to twelve student payloads to an altitude of about 36 kilometers with flight durations of 15 to 20 hours using a small volume, zero pressure balloon.  It is anticipated that the payloads carried by HASP will be designed and built by students and will be used to flight-test compact satellites or prototypes and to fly other small experiments. 

A launch of a HASP payload in 2013:

The program, sponsored by NASA and the Louisiana Space Consortium, seeks

to foster student excitement in an aerospace career path and to help address workforce development issues in this area. HASP plans to provide a “space test platform” to encourage student research and stimulate the development of student satellite payloads and other space-engineering products.  By getting the students involved with every aspect of the program HASP hopes to fill the gap between and student built sounding balloons and satellites, while also enhancing the technical skills and research abilities of the students.

One experiment on a flight in 2014 measured very low frequency sound waves, referred to as infrasound, at high altitudes for the first time in decades: Eerie ‘X-Files’ Sounds Recorded From the Edge of Space – Discovery News

Here is a sampling of what they recorded:

Here’s the caption to the video:

Infrasound recorded on a high altitude balloon during the 2014 HASP flight. The balloon floated at approximately 22 miles above sea level for 5.6 hours, travelling about 450 miles in the process. The research was featured in articles on Live Science and the Huffington Post as well as featured on the BBC and National Public Radio.

The sound has been sped up 100 times in order to bring it into the audible range. The original clip featured in the media was sped up by 1000x (see the video “Infrasound in the Stratosphere II), and thus had less audible detail.