Since the acoustic impedances of air and solid medium are not in the same order, the acoustic wave transferring in the air would be theoretically fully reflected on the solid surface. So my question is, what if the acoustic wave is strong enough to vibrate the solid medium? Is that kind of wave transmission or how can we describe that?
There is extensive literature on this subject. Why don't you start with the classics: Stress Waves in Solids by H. Kolsky, Dover, 1963, and other editions.
Vyacheslav Ryaboy Thank you for your reply. I have read similar books like Ultrasonic testing of materials by Krautkrämer, and Wave motion in elastic solids by Karl Graff. After rechecking the reflection equations on boundaries, I found that I had wrong result for the case of wave transmission from air to solid. The transmission coefficient is actually approximately 0 for the reversed case, that is from solid to air.
If I may join the discussion?
You assume normal wave incidence and, thus, implicitly that the wave is a longitudinal wave. For such cases, sure, the mismatch will be great. However, some power is transmitted. If memory serves, water to air implies a 30 dB isolation. May look like a lot but, we have ordinary double partition walls that do 60 dB isolation - easily.
When there are more wave types, eg bending waves. For these, we have the coincidence phenomenon (aka Snell's law) which provides an angle at which transmission/radiation is total.
[The nxt speaker builds on the coincidence phenomenon. It had a honeycomb plate with a low coincidence frequency. ]
For soil vibration, surface wave speeds tend to be in the ballpark of the wave speed in air. Consequently, the wave energy may jump back and forth between the soil and the air. Not what one would inuitively assume.
[Disclaimer - the soil/air observation - I've never measured it myself but have been informed by soil dynamics experts that this more often than not tends to be the case]
So, it all very much depends on the situation
BTW - last millenia, ie pre PDF - PhD = Doctor of Photocopying
Difference between sound and vibration is , vibration waves travels through solid medium whereas sound waves travels through air
I mean... consider the experiment where the sound waves make the wine glass shatter. It's a phenomenon.
Theoretically fully reflected... but not "fully fully"... sure, most of it bounces off.
Case 1. Blast wave.
It is a "sound" also. Explosions do push walls fairly well.
Case 2. Resonant frequencies.
Lower energy content? Waves that can barely move an ear drum - bouncing off of a concrete wall? Sure... But can still resonate with the natural frequencies within components, and natural frequencies within volumes of materials. Standing waves within "solids" are a real thing.
If the room / building has acoustics resonating at certain frequencies - those will get amplified quickly. So, even microscopic amounts of vibration - become enough to make the solid vibrate.
Technically, damping, internal damping... is the only thing stopping things like acoustic powered super-sonic hammers... from shaking the anchors out of the the building.
Claes Richard Fredö Thanks for your detailed reply.
- I did indeed assume that the incident wave propagation is normal to the boundary and the wave is simply considered as a plane wave. However, I did not mention that in my question, which may lead to misunderstanding. For the assumption as a plane wave, the wave transmission/ reflection property should hold its validity for both longitudinal and transverse wave forms.
- I encounter quite often terms like p-wave, surface wave, lamb wave etc. But still, I can't tell the minimal differences between some terms. For instance, I understand that p-/s-waves are referred to as wave propagation inside an unbounded medium, and surface wave like Rayleigh wave is then referred to as wave propagation near the solid surface, which is 1d bounded. But what is the difference between lamb wave and bending wave or are they comparable?
- For oblique incident wave, there is indeed an angle at which there is no reflection and therefore complete transmission. The angle is referred to "angle of intromission" (according to "Fundamentals of acoustics" by Kinsler) For the case in my question, that is from air to solid, there will be such an angle. Thanks for that information. I did some homework ;)
- I am not familiar with the soil - air case but I will take it as a hint and do some deeper research.
- I'm having (attending) permanent head damage (PhD), which may be a little bit comparable to the Doctor of Photocopying case ;). I am actually a civil engineer but somehow doing disciplinary research about structural health monitoring, which involves a lot of wave motion theory, system theory, and some others. Hopefully, I will find my way someday.
Amit Bhende Thank you for your reply.
If we extend the term "vibration wave" a little bit, it seems that all mechanical wave modes originate from particle disturbances, which may be referred to as vibration. But I understand what you mean.
Tomas Sabaliauskas Thanks for your reply.
I totally agree with the resonant case you mentioned, which is caused by the standing waves. I would intentionally discuss the case of propagating waves as I raised the question. But of course, the resonant case is certainly a case, where the a great amplitude in the solid structure can be observed.
I may say that sound and vibrations are deeply linked, in both directions.
Have a look at the simple Rayleigh integral approxmation of sound pressure coming from a vibrating plate: Article On the Influence of Scattered Errors over Full-Field Recepta...
Sure, the flexibility and damping of the medium plays a role, but you get energy transfers (and dissipation) from gas (air) to liquid to solid, and viceversa.
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