Sounds are heard everywhere in nature, except in the vacuum of space. Humans and animals often rely on sound for communication, navigation and location information. When humans need to interpret sounds above the range of hearing, an ultrasonic circuit can create, send and receive high frequency signals.
Ultrasonics are sound waves with frequencies higher than human ear can normally detect. Typical ultrasonic frequencies are greater than 20,000 Hertz (20 kHz), or cycles, per second. High frequency sounds have a wide range of uses, including distance measuring, medical uses, and security devices.
Sound waves can be used to measure distances. An ultrasonic circuit can create a high frequency sound pulse of short duration that will travel through air or water, measuring the amount of time for the pulse to return to the device. Software then calculates the distance to the object. The speed of sound is different depending on whether air or water is present, so the software may correct for the type of water, temperature and density.
Sonar, or sound navigation and ranging, is used in ships and submarines for navigation and detection. This is an ultrasonic circuit using transducers to send and receive the sound pulses for detection of other vessels or underwater features. Short pulses are used rather than a continuous frequency to provide more sound energy for accuracy.
Another use of sonar ultrasonics is for inspection of underwater structures, geology, and search and rescue. Portable sonar devices can be attached or towed behind surface ships. These devices send ultrasonic pulses in desired directions and create images of undersea structures based on the reflected sounds. Fish finder devices used on private and commercial fishing vessels use a similar system to detect schools of fish below a boat.
An ultrasonic circuit can be used as a medical imaging device, and is typically referred to as an ultrasound machine. The circuit produces a focused ultrasonic frequency in a hand-held probe that can be placed on a patient's body. Software processes the reflected sounds and creates an image of internal organs on a monitor. The resulting images can be used for medical diagnostics, observation of heart and blood vessels, and prenatal observation of a fetus, or unborn child, inside the mother.
Ultrasonic frequencies can travel through solid materials and can be used as a diagnostic tool. A portable device similar to an ultrasound machine can be used on bridges, pressure vessels, or other equipment to look for internal flaws or cracks prior to failure. This technology is used for non-destructive testing of aircraft structural parts during routine inspections. It can find very small cracks and fatigued areas from repeated takeoffs, landings and in-flight stresses.
Sound can be used to provide signals used for security systems. The principle is the same as sonar or ultrasound, with a frequency sent and received by an ultrasonic circuit. In this case, any received signal indicating movement can trigger an alarm circuit. These systems can be used where infrared, or heat sensing, security systems do not operate correctly due to temperature or other conditions.