Build a Parametric Speaker of Your Own.
At the Hacker Hotel conference in the Netherlands, [Orange_Murker] presented an ultrasonic parametric speaker. It projects an extremely narrow beam of sound over a significant distance, but it’s not an audio frequency speaker at all.
![[ImageSource: Orange_Murker]
Those of you familiar with radio will recognize its operation; an ultrasonic carrier is modulated with the audio to be projected, and the speaker transfers that to the air. Just like the diode detector in an old AM radio, air is a nonlinear medium and it performs a demodulation of the ultrasound to produce an audio frequency that can be heard.
[Orange_Murker] spends a while going into modulation schemes, before revealing that she drove her speaker with a 40 kHz PWM via an H bridge. The speaker itself is an array of in-phase ultrasonic transducers, and she demonstrates the result on her audience.
<https://media.ccc.de/v/2025-201-build-your-own-parametric-speaker>](https://nerdculture.de/system/media_attachments/files/114/172/381/612/832/329/original/419ed72e02265621.png "[ImageSource: Orange_Murker]
Those of you familiar with radio will recognize its operation; an ultrasonic carrier is modulated with the audio to be projected, and the speaker transfers that to the air. Just like the diode detector in an old AM radio, air is a nonlinear medium and it performs a demodulation of the ultrasound to produce an audio frequency that can be heard.
[Orange_Murker] spends a while going into modulation schemes, before revealing that she drove her speaker with a 40 kHz PWM via an H bridge. The speaker itself is an array of in-phase ultrasonic transducers, and she demonstrates the result on her audience.
<https://media.ccc.de/v/2025-201-build-your-own-parametric-speaker>")