Some mechanical Vibrations are in deed good !

NVH Engineers are all the time interested in killing mechanical vibrations of vehicle-components or systems since they cause human discomfort up to 80 Hz and their structure-borne sound till1k Hz is a dominant part of overall in-cab noise perceived by vehicle passengers.

But there are some good non-automotive applications of the vibrations serving human-beings:

1. Snake Repellents:

Snakes have poor eyesight and they cannot hear sonic waves transmitted by the air. To make up, they sense vibrations transmitted from ground by their jowls as a signal of danger.

Here, keeping a vibrator on the ground to scare snakes away from a residential area is found useful. Generally, such small vibrators use ultrasonic frequency range near 25 kHz with very low acceleration (< 0.01 g level) so that the human beings are not disturbed by floor vibrations or sound emitted by them. Apart from snakes, they repel rodents and insects, too.

2. Human body healing

Low-magnitude (~0.1 g) vibrations from 20 to 50 Hz have been shown to stimulate bone formation & increase bone density, making them a promising approach for preventing osteoporosis and thus reducing the risk of fractures.

For muscle relaxation and circulation enhancement, frequencies ranging from 50 to 200 Hz, with similar 0.1 g levels, are widely seen in the Vibrational Therapy devices or body-massaging centres.

Research is in progress w.r.t use of low frequency alfa waves (8 to 12 Hz) or neural oscillations to target specific regions of the brain for therapeutic (or calming) purposes against chronic pains of the body.

3. Dental Care:

Vibrations are used for procedures such as ultrasonic scaling and tooth cleaning (to remove plaque and tartar from teeth) where frequencies range from 20k to 50k Hz with amplitudes kept in a safe but effective limits from 0.1 to 2 g.

4. Energy harvesting

A process of converting mechanical vibrations or oscillations into electrical energy is becoming popular:

Applications include:

-powering wireless sensor networks for structural health monitoring in buildings, bridges, and other infrastructures.

- Powering wearable devices using human motion.

- Extending the battery life of low-power electronics in remote or inaccessible locations.

Here, both frequency and amplitudes can have a wide range: 10 to 10k Hz and 0.1 to 10 g, depending on stiffness of the harvester element.

There could be many more such interesting positive applications of the Vibrations! How and where they are used with what frequency & amplitudes will decide their effectiveness, right ?