Producing an intense beam of low frequency sound

What is it about?

We exploit nonlinearity in the air to convert ultrasound into low frequency sound. This allows the low frequency to be beamed in a way that is impossible with an ordinary loudspeaker.

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Why is it important?

We developed this technique not for audio applications, but for safe landmine detection. From stand-off distances we can send a beam of sound into the soil and measure the resulting surface vibrations with another sensor (laser or microwave). The whole system is Open Source Hardware and Software.