Ceiling and floor reflections are on the cone of confusion and therefore might only affect timbre at lower frequencies.
Again - can You please post any reference for this?
I mean an explanation when a reflection can be treated as a specular reflection having regard to the wavelength and to the distance to the reflecting surface? Please be so kind. I would be very grateful. 🙂
Regarding the issue of similar binaural values for the ceiling and floor reflections: I may might need to disagree with myself. I am still thinking this one through
I'm in the design phase of my new loudspeakers, and exploring the floor reflection contribution therein I made some FDTD simulations of the case.
The simulated waveform is a gaussian wavelet like this:
The simulation includes reflective floor and ceiling. Vertical ends are absorptive. x and y grids are in meters.
Here is 0.8m tall dipole baffle with 12" element at 20cm above floor (to the center) at 500Hz: There got some edge diffraction from the baffle but no distinctive floor reflection.
For reference here the baffle is elevated 1m above floor and element in the center of the baffle at 500Hz: Here a clear floor reflection is seen.
- Elias
The simulated waveform is a gaussian wavelet like this:
An externally hosted image should be here but it was not working when we last tested it.
The simulation includes reflective floor and ceiling. Vertical ends are absorptive. x and y grids are in meters.
Here is 0.8m tall dipole baffle with 12" element at 20cm above floor (to the center) at 500Hz: There got some edge diffraction from the baffle but no distinctive floor reflection.
An externally hosted image should be here but it was not working when we last tested it.
For reference here the baffle is elevated 1m above floor and element in the center of the baffle at 500Hz: Here a clear floor reflection is seen.
An externally hosted image should be here but it was not working when we last tested it.
- Elias
Here a snapshot at the time the wave has travelled 3m.
For comparison. 500Hz.
Floor baffle. Nice spherical wavefront. No tail 🙂
And elevated baffle. Look at that carbage following the direct sound 😛
- Elias
For comparison. 500Hz.
Floor baffle. Nice spherical wavefront. No tail 🙂
An externally hosted image should be here but it was not working when we last tested it.
And elevated baffle. Look at that carbage following the direct sound 😛
An externally hosted image should be here but it was not working when we last tested it.
- Elias
I searched a bit, couldn't find anything that was specifically on-point. 😱
Rather than an affirmation, what's the point of diffraction (which does specifically relate to a wave's length and necessarily distance to an otherwise reflective surface)?
It is confirmed. I definitely disagree with my self.
At 0 or 180 degrees (front and back), the binaural cues for the direct sound, ceiling bounce, and floor bounce are all the same. However this is a special case. Off axis the "bounce" will not fall along the cone of confusion (for the direct sound). The binaural cues will differ from each other and also differ from the direct sound. The discrepancy gets larger as the sound source get closer to either of these boundaries.
I have admitted my mistake and I now feel better about myself. Insert smiley face somewhere
I have to disagree with myself too. The floor and ceiling reflections are not on the cone of confusion. If the ears would be in the floor plane then the floor reflection would be on the cone of confusion.
For a driver at 100cm from the floor, ear height at 95cm and a speaker distance of 346.4cm the interaural time differences are as follows:
Direct sound: 0.25ms
Floor reflection: 0.21ms
Ceiling reflection (ceiling height 2.4m): 0.19ms
For a driver at 100cm from the floor, ear height at 95cm and a speaker distance of 346.4cm the interaural time differences are as follows:
Direct sound: 0.25ms
Floor reflection: 0.21ms
Ceiling reflection (ceiling height 2.4m): 0.19ms
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great thread, isn't it? 😀
everyone is in disagreement with oneself
most probably I will be as well, but I am not that fast thinker - still thinking 🙂
me neither 🙁
but there certainly must be some formulas which make possible making such simulations as the one posted by Elias
I don't know - what is it?
Originally Posted by graaf
Again - can You please post any reference for this?
I mean an explanation when a reflection can be treated as a specular reflection having regard to the wavelength and to the distance to the reflecting surface? Please be so kind. I would be very grateful.
Wouldn't it (in this case) have been sufficient to construct the mirror source (through the floor) of the woofer? This would have shown, how the reflection is only a few degrees off the direct sound.
Sorry, calculation error, ITD for the ceiling reflection is 0.18ms
I've also calculated the overall delay of floor and ceiling reflection relative to the direct sound:
Floor: 1.51ms
Ceiling: 3.01ms
Not sure what to conclude from those numbers.
But does our auditory system know anything about degrees as such?
Isn't it that all it senses are pressure fluctuations in time?
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I am not sure what Markus did calculate and how but can anyone who understands calculate the same for a driver at 20 cm from the floor?
Did the same calculations for a speaker with a distance of 231cm instead if 346cm.
Reflection delays:
Floor = 2.08ms
Ceiling = 3.95ms
ITD:
Direct = 0.25ms
Floor = 0.18ms
Ceiling = 0.15ms
Reflection delays:
Floor = 2.08ms
Ceiling = 3.95ms
ITD:
Direct = 0.25ms
Floor = 0.18ms
Ceiling = 0.15ms
Of course not. "Degree" is just a mathematical term.
Sure. But if two waves travel almost parallel, their phase relation doesn't change significantly on their way. So they are sensed as one.