DIY Ultrasonic Directional Speaker: A Deep Dive into Construction and Design

Building this ultrasonic directional speaker was both challenging and rewarding, offering unique possibilities in creating sound that travels in a narrow beam, perfect for focused audio transmission. The core of the system centers around a custom-printed circuit board (PCB) that houses individual 40 kHz ultrasonic emitters. This frequency is well beyond the range of human hearing but can be modulated to carry audible sound, which listeners can experience when positioned within the beam’s direct path.

Powering the system is a robust 7.4V lithium-ion battery pack, capable of supplying enough current to sustain the entire setup for hours. The battery output is boosted to 24V using a DC-DC boost converter, which is essential for driving the ultrasonic transducer array at optimal power levels. This boosted voltage is then fed into an H-bridge controller, which drives the array, generating the high-frequency ultrasonic waves needed for directional sound transmission.

To handle the power requirements of the smaller electronic components, a buck converter steps the 24V down to safer levels for the rest of the system. This includes a classic 555 timer circuit, which modulates an audio signal, shaping it into pulses that can drive the ultrasonic transducers effectively. I also included a small Bluetooth receiver, which acts as the audio source. This enables seamless playback from any Bluetooth-enabled device, whether it’s music from a smartphone or audio from a tablet, creating a user-friendly experience with a wide range of potential applications.

The result? Sound that only the person directly in front of the speaker can hear, making it ideal for applications like private audio listening or targeted announcements. This speaker offers an incredible level of audio focus that conventional speakers can't achieve, creating new possibilities in the realm of personal audio and public installations.