Frequently Asked Questions

1. What is ultrasonic noise?

Ultrasonic noise is any sound above 20,000 Hz. At best, humans can hear in the sound frequency range of approximately 20-20,000 Hz (20,000 Hz = 20 kilohertz, or 20 kHz). Many other species hear very well in the ultrasonic frequency range above 20 kHz. For example, dogs and cats can generally hear up to about 40 kHz and mice can hear up to approximately 100 kHz.

2. Why is ultrasonic noise so useful to industry?

Mechanical systems showing early signs of wear and leaks in gas/fluid lines produce ultrasonic noise. By the time a mechanical system creates enough friction to vibrate or make noise that we can hear, much of the damage is already done. Very early on when a system is producing friction, the noise made by this friction is much higher frequency, in the ultrasonic range. We can detect such changes with ultrasonic measurements, allowing early detection of problems. 

3. Why should biomedical research facilities care about ultrasonic noise?

Over 95% of all animals used in biomedical research are rats and mice. Rats and mice hear in the ultrasonic frequency range (above 20 kHz), and hear very poorly in the range of human speech. There are many sources of ultrasonic noise in biomedical research facilities and laboratories, such as fluorescent lighting, motors that run the ventilated caging systems so common in animal facilities, computers, etc. Humans cannot hear in the ultrasonic frequency range so we have no idea what our research animals are being exposed to. Anybody who has worked or lived in a noisy environment knows how stressful background noise can be. This background noise can serve as a stressor for lab animals, impacting hormonal systems in animals and thereby impacting virtually every area of biomedical and behavioral research. Ultrasonic noise serves as a "quiet" confound to biomedical research, disrupting research animals and adding variability to our measurements, resulting in greater statistical ambiguity in our research and the need for more animals.

4. How often should ultrasonic noise measurements be taken?

For Biomedical Research Facilities: Every biomedical research facility should have a comprehensive ultrasonic noise audit conducted yearly. Ultrasonic testing (as well as noise we do hear) should also be conducted whenever there is construction going on, when new equipment is brought into the facility (cage washers, ventilated caging equipment, etc.), or whenever personnel notice major changes in animal behavior indicative of stress.

5. Why should biomedical research facilities care about vibration?

Vibration is a known stressor of lab animals. Indeed, it is used to induce stress in a number of models. Day-to-day vibrations experienced by animals include building ventilation, rack ventilation motor, movement of personnel and carts in the facility, operation of equipment with moving parts such as ventilated caging systems, cage washers, etc., and movement of neighboring animals. Vibration is known to have many of the same negative impacts on animals as does noise. It can lead to changes in breeding, food intake, weight gain, and a number of other physiological effects involving cardiovascular and stress pathways.






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