ULTRASONIC LEAK DETECTION

What is ultrasound?

Sound has been defined as vibration of an air column to which a human ear would respond. Ultrasound is those frequencies that are above human hearing. Humans can usually begin to hear low frequency sound at about 30 Hertz (cycles per second). This is comparable to the low bass frequencies in a good music system. The upper range for high frequency hearing is usually in the neighborhood of 15,000-20,000 Hertz or 15 to 20 kilohertz.

Even though we humans don't have much sensitivity to the higher (or to us, ultrasonic) frequencies, these sounds exist in nature. Bats use high frequency sonar to zero in on flying insects at dusk. Crickets rub their legs together and generate considerable high frequency noise as part of the chirp that we hear. It is interesting to listen to crickets or bats with an ultrasonic detector. Some species of fish use very low frequencies for communication of a sort, and others use high frequencies. Rodents can communicate at frequencies above our hearing range. Dogs and cats have high frequency hearing sensitivity above our limits. The so-called "silent dog whistles" generate high frequency sound that dogs can hear but humans cannot.

What is an ultrasonic leak detector?

An ultrasonic leak detector is designed to listen for sound in the 40 kHz range. These instruments are used to pinpoint pressure or vacuum leaks, detect mechanical wear of bearings or brushes or locate electrical arcing or discharge. As something is passing through a hole, crack or crevice, thr friction generates ultrasound at 40 kHz or above. The instrument will detect this sound. You can also create sound at 40 kHz through a tone generator or a transmitter. The transmitter is used to fill a tank, cargo hold or an enclosed structure. Sound does not pass through things but will seek to escape at any hole or crack in a seal, hatch cover, door, etc. Again the instrument will detect this leaking sound.

What is a cargo hatch ultrasonic leak detector?

The hatch cover ultrasonic leak detector kit is comprised of three components. You have a receiver to capture and display the sound; a microphone on a wand to search for the leaking sound and a transmitter that is placed inside the cargo hold to generate the sound.

The transmitter is placed in the center of the hold. The transmitter has 19 emitters placed at different angles pointing upwards generating a tremendous amount of sound at 40 kHz. The sound is bouncing and ricocheting in the hold looking for a crack or hole in the seal of the hatch cover to escape.