How to make ultrasound audible?

1. How do I make audible ultrasonic sound?
2. Are ultrasounds audible?
3. What produces the sound from an ultrasound?
4. Why is the sound of an ultrasound equipment not audible to us?

How do I make audible ultrasonic sound?

Through signal processing, ultrasound can be converted into a secondary "downmixed" signal in the audible range. In the heterodyne method, a narrow frequency in the ultrasonic range is selected (e.g. carrier frequency of 40 kHz +/- 2 kHz) and transformed into the audible range via difference frequencies.

Are ultrasounds audible?

High frequency sound and even ultrasound in the lower frequency zone (up to 24 kHz) can be audible if the sound level is high enough. The sound threshold (the sound level where sound can be perceived) rises sharply once the frequency (and therefore, the tone) becomes higher.

What produces the sound from an ultrasound?

In most cases, the active elements in ultrasound transducers are made of special ceramic crystal materials called piezoelectrics. These materials are able to produce sound waves when an electric field is applied to them, but can also work in reverse, producing an electric field when a sound wave hits them.

Why is the sound of an ultrasound equipment not audible to us?

Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it.