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Old 29th June 2010, 04:04 AM   #1
d3cibel is offline d3cibel  Indonesia
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Talking About cabin gain and in car standing wave

Is the primer standing wave frequencies in a vehicle can be measured with wavelength calculator ? Assume i just measure the main paralel panels in the car : Height , Width and Length of the car.
Will be the car's cabin gain will somewhere on those main standing wave frequencies ?Any comments will be very appreciated
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Old 29th June 2010, 06:46 AM   #2
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You should have watched Xhibit presenting the MTV show of hot rodding
If the space between panels is full of objects,seats,skulls&shoulders ,everything reflective ,and diffracting ...
it doesn't happen .
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Old 29th June 2010, 09:24 AM   #3
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Wink Standing Wave

Yes i agreed with u that in the car everything was reflective and deflective .But the main dimension of the car interior wont change even we stuff a lot of things in it, its about the paralel walls that create the standing wave.
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Old 29th June 2010, 09:43 AM   #4
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R U sure ? A standing wave usually happens in a large ambient ,and you hear it because of the very slow decay of it ,it is just a permanent single tone that overhangs music . As reflections and diffractions happen naturally ,there are some tricks to eliminate them ,such as carpets on the floors ,libraries on the walls ,etc. ;which is not the case of a car ,where I think if it ever happens (R U sure you're not talking about resonances ?) -and it may happen at certain frequencies -it is negligible .
If you report such phenomenom it's about time to take some precautions
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Old 29th June 2010, 09:57 AM   #5
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Talking Standing Wave

Standing wave will occur in every chamber , which is got some parallel walls in it.Regardless its a small room or big room.If we put some sweep test tones in those chambers we will see peaks and valleys in it.
The in phase standing wave will enhance each other and reinforce each other at a particular frequency and those out of phase standing waves will create dips.
In my case, its not about diminishing the standing waves.Because my purpose is on car SPL , i want to reinforce a particular in phase standing wave at my calculated frequency, so i can create a maximum peak at the frequency to gain maximum SPL.Is my thoughts can logically accepted ? Or maybe im just misunderstand about this standing wave thing ?
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Old 29th June 2010, 10:13 AM   #6
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Hi d3cibel.
If math is right ,what you'll hear inside a cab with parallel panels will be something like a low -mid tone at about 200 Hz ,since 1,72 m being its wave length . 344/200=1,72 .
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Old 30th June 2010, 05:33 AM   #7
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Talking Standing wave

I calculate the main internal dimension of my car , which i assume got the obvious standing wave, Length from the front windshield to the rear windshield = 257 cm , Height from roof to floor = 130 cm ,and Width from passanger side window to driver's side window=135 cm. 343 m/s divided by 2 x Length in metre.
The result is like this = 66.7 Hz ,127 Hz, 131.9 Hz and for full wave.So roughly i got 3 peaks , maybe can be verified also by the transfer function searching method(havent done it yet,soon will).
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Old 30th June 2010, 07:36 AM   #8
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Quote:
Any comments will be very appreciated
Yes ,I got sick of thinking about invisible waves ,in the morning...
makes me feel..vacuum !!
The big mistery for me , in car audio ,is how is it possible to have full rate bass.
Below 200 Hz-lower freq if a big cab - as you said ,peaks of a (hypothetical ) single sine wave , happen only at 1/4 or 1/2 of the WL . before completing each a single cycle ,the wave has already hit a surface and ,being reflected ,looses some energy .So there's no reinforcement YMHO and no production of disturbing low tones .
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Old 30th June 2010, 11:03 AM   #9
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Talking Standing wave

Well cars are the worst environment to listen to music.But this is the best part of it , and make car audio very interesting.One must overcome many difficulties.
Maybe sharing thoughts with u can open a new dimension about sound for me.
I try to study car interior acoustics nowadays,and havent find solution about my questions.
I think the bass sound will be powerful if the direct radiating source reinforced by the reflecting waves from the interior ,arrived in the same time,frequency and phase at the Mic or listener..What do u think ? U on car audio too ,bro ?
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Old 30th June 2010, 11:28 AM   #10
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no!I don't have even a driving license!Then ,working inside the car is a real PITA ! I imagine that car environment with associated noise brings to push always to more SPL needs. But high SPL contests for me are beyond ny knowledge . Just think you are inside (well -in contests there's nobody inside !)
a very big vented or closed box ...
I think you're moving in the right direction ,D3cibel .
Since distances are relatively short -compared to wave lengths,specially the high ones - putting two drivers that play the same tone ,for example a 345 Hz tone -WL=1m-varying the offset of 30 cm between them ,you'll get an exact 180 phase rotation...called destructive interference ?? YES !
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