- Author
- Not stated
- Published
- 2024-09-12
- Kind
- Personal hardware project write-up, with a built prototype
- Original
- maurycyz.com/projects/speaker/
- Subject
- Systems and hardware
- Themes
- What the senses do
What it is
The page gives no author name. The author built a narrow-beam speaker for rickrolling pranks.
What it says
- Strong modulated ultrasound turns into audible sound in air, which allows a small directional speaker.
- The prototype wires 73 ultrasonic transducers together on an 18 cm by 6 cm board.
- The driver uses a 555 timer, an op-amp for pulse-width modulation and an H-bridge.
- The author reports a beam of sound only a few degrees wide.
- Sound is louder when bounced off a hard wall than when heard directly.
- The author calls it a poor speaker, with virtually no bass and easy distortion.
- The author gives asin(wavelength / (2 * size)) as the angle of the first null.
What evidence it gives
The post offers one working prototype with a described circuit and some recordings. It gives a plain explanation of beam width and one formula. It lists no measured beam angles or loudness figures.
Interests and limits
Only the text was read, and the schematic, photos and audio clips were not viewed. The reflection effect is the author's guess. No measurements back the beam width. The post tests no other designs. The author says it is not a good speaker.