Recent content by Alfred Cann

glass?? There is no glass in the window!

I don't think you have made your case at all with that really irrelevant citation, and I think that I've made mine pretty well with the paper I cited. And I'm surprised that no one has yet joined this thread (except for one early post by tech99). In the case I was analyzing, the wall was...

I have looked at the 2009 paper you sent. It is almost totally irrelevant. The slits are mostly much narrower than the wavelengths of interest. Furthermore, in many cases they are really ducts of considerable length (what they call depth). This paper comes from the community of noise suppression...

Just found what I was looking for: Wright, Julian, Radiation Impedance Calculations for a Rectangular Piston, Journal of the Audio Engineering Society, V. 38, No. 5, May 1990, pp. 350-354, Fig. 2 and others. Confirms my conjecture that for rectangular apertures the slope of the radiation...

Sorry, what is FEM?

trurle said: "1. Velocity part along wall do not transfer sound through aperture. " My point exactly -- that energy is lost and not propagated forward. It's like trying to pump up a tire when the air hose has a big leak -- the tire will not get pumped up. "2. The slot/opening still transmit...

1. Remember, a rigid wall is a node only for velocity perpendicular to the wall, not along the wall. 2. Forget the Chinese paper; it's probably not relevant. We already know from the loudspeaker and round aperture literature that the response is a highpass filter, as I have described. And a...

trurle: The NASA paper you cite is completely irrelevant; it deals with fluid flow (as used for sound absorption) not with sound transmission or radiation. Note that their apertures are much smaller than a wavelength; mine are of the order of the wavelength. Look at the literature for radiation...

Thank you. I still would like to know, just for academic interest, if my analysis of a slot in an ideal wall is correct.

There are many confounding factors: 1. Multipath effects in dining room and kitchen 2. Electric bass speaker on the floor and behind the player, thus not in exactly the same location as the center of radiation of the acoustic bass 3. Radiation of the acoustic bass from a much bigger area...

To solve a complex problem, I always approach it with simplifications first, in order to develop basic insights. So let's stick to my statement of the problem with negligible wall thickness. In case you're interested, this problem arose in connection with the propagation through the 1x5 ft...

1. Most bird and butterfly colors appear quite angle-insensitive, not even Fabry-Perot. Is the literature wrong that I have read, that attributes these colors to interference?

I have long been puzzled by the colors of bird feathers and butterflies. They are mostly attributed to interference in microscopic structures, not dyes, yet do not display the typical change of color with viewing angle of interference colors. Why? There are a few exceptions; some butterfly spots...

I am stumped analyzing the transmission of sound through a rectangular slot in a thin rigid wall. I have found online that a square or round aperture acts as a highpass filter with a 6dB/oct slope and a corner frequency where the wavelength is on the order of twice the aperture diameter...

I had assumed the spring constant is invariant; you guys are implying that it changes.