Wave can be called a visual descriptor of an infinite change to matter. Waves can transfer energy or matter based on their type, wether they are electromagnetic, matter waves or mechanical. In current case I will mention only mechanical waves, as they are the base of the title "Vibrational Stimulation".
Before diving deep into vibrations and how they can be used to stimulate human, its nervous system, etc., it's better to get more familiar with the vibration. As mentioned previously, vibrations come from mechanical waves. A mechanical wave is a traveling force within atomical/molecular structure of a medium that was caused due to an exposure to an external force (i.e. pressure), so force is always present, in other cases when force isnt present, it's called Free Vibration but even then the medium was initially disturbed. Nevertheless, let's return to description of a mechanical wave rather than trying to protect importance of a mechanical force. The type and rate of occurance of a mechanical wave determines it's presence in a visible world. There are 2 types of mechanical waves: Transverse waves travel through the material causing disturbance in all directions or disturbance in all direction causes a wave to travel through the material, where Longtitudal waves travel parallel to the material without causing break in the medium, only it's temporary shift. For example: guitar string moves (Transverse wave), but produced sound (Longtitudal wave).
Vibrations are made out of occilations of the transverse mechanical waves. Occilations mean that they repeat, and this repetition is the main descriptor of a well-known meaning of "Vibrations". Well-known to use understanding of Vibration is that it giggles and creates sound, this is only possible because of fast giggles of the molecules with medium. Rapid cycling of the wave creates sound and it generates noticable build up to be felt within and through the medium.
Interesting fenomena: Why certain types of sound make the medium vibrate?
Apparently when searching on what is sound, you can find this piece "Sound typically travels as a longitudinal wave, where particle vibrations occur in the same direction as the wave propagation. In solids, sound can also propagate as transverse waves The wave consists of alternating compressions and rarefactions, which are regions of high and low pressure moving through the medium. The speed of sound depends on the medium's properties, such as density and elasticity, and is approximately 343 meters per second in air at room temperature" - Source: Vedantu .
And there is also different properties of sound like pitch, timbre and loudness. BEST SETTINGS FOR PENETRATION ...
So sound can be a penetrating mechanical wave, mildly interesting. An ignorant person would think to use penetrating properties of sound for stimulation methods, the loudness must be enormous, but is that so... Maybe there is a way to utilize properties and reach similar penetrating effect. MAYBE /:> But for now it's impossible, and closest are: 1 Sonic Weapons; 2 Ultra Sound; 3 Infrasound. Infrasound which less familiar is a Very low frequencies have extremely long wavelengths. For example, a 10 Hz sound wave in air is about 34 meters (112 feet) long and generating noticeable infrasound efficiently often requires large vibrating surfaces, large enclosures, or very powerful equipment. (You usually can't hear it, but you can feel it as vibration or pressure).
For example take a string with a weight at the end and start rotating it in the air, if you start rotating it fast, the fast penetration of the weight within the air medium will create sound. Similarly with fast friction or pressure, it creates a chain-reaction (WAVE) within molecular structure and it's fast change generates sound and vibration.
How can this be used for stimulating human body?
Human body, the skin, and neurons below it are very sensitive to different influensors. Have you ever felt dopamine, with smallest flow of air over your skin or just looking at something or hearing something not special/thoughtless made you feel good, or in other words caused release of dopamine. You may relate to what is being described, but it may be a good moment. Similarly, let's speak about moments when words feel differnet, or to put it simply the chaoticness of touch - What I am trying to bring you, dear reader, is sequences. Sequences matter in the usage of the stimulation.
Not only it's very safe, because it doesnt introduce heat as electrical stimulation/ultra sound that desrupts and heats up neural activations OR as sound stimulation and visual that causes fast reaction from body - It gently effects nervous sytem BUT for it to work it must be correctly sequenced
Summary
Vibrational stimulation is a perfect, state-of-the-art method for stimulating human nervous system non-invasevly and safely without causing overheating, degeneration of neural cells and obviously tissue. The complexity of this method is that it requires precise engineering of the stimulation sequences a.k.a. Magic.