Can you ID these sensors for me? (Hop! Suitcase sensors)

Do you remember the Hop! Suitcase, the one that follows the Bluetooth signal in your cell phone around the airport?

Well, I found a picture of the Hop! in prototype. The pic has the sensors in view and I’m curious what they are. I expected to see antennas, but these look like microphones.

What do you think?

Ahhhh... They're ultrasonic senors. — Maxbotix Ultrasonic Rangefinder - LV-EZ1 [LV-EZ1] : ID 172 : $24.95 : Adafruit Industries, Unique & fun DIY electronics and kits

Guess the suitcase didn't triangulate the Bluetooth signal after all.