3rd order+Noise
3rd order+Noise
(OP)
I have heard that 3rd order is Sporty sound source? Can anyone explain me the meaning & physical significance of order in terms of NVH, that would be a great help
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RE: 3rd order+Noise
For example, 3rd order indicates the frequency that is 3 x the engine rotational speed; if an engine is turning at say 1200 rpm, or 20 rps, 3rd order would be a frequency of 60 Hz (3 x 20 = 60).
Third order is engine firing frequency for 6-cylinder (4-stroke) engines, so I'm not sure it relates to "sporty sound" for anything other than 6-cylinders. You'd be very unlikely to encounter a significant 3rd-order component of the exhaust noise in for example a V-8 engine.
RE: 3rd order+Noise
Sporty sounds tend to have an order balance that comprises the fundamental, plus a good contribution from the first few harmonics. For a 6-cylinder engine, this would be 3rd, 6th, 9th, 12th, etc. Half orders (a term used to describe orders that aren't harmonics of the fundamental, but are harmonics of the 1/2 order) tend to give a rougher sound.
Many many dollars, euros & yen are spent in refining the sound quality, usually through modifications to the order balance.
Sometimes roughness needs to be added to a vehicle's sound to match the rough, tough image required. Sometimes smoothness is required. Sometimes downright aggressive power is required. These can usually be obtained from the same base engine, by modifications to the exhaust and intake system geometries.
RE: 3rd order+Noise
1. Like when engine will run 6000 rpm than I will worry about 100 hz so than why people study upto 1000 Hz or may be more? (due to other components?)
So the Plot for Noise vs Frequency should be from 0 to 100 Hz?
2.If i see any pick at specific rpm & i would like to reduce that peak Noise(dB) how could i achieve it at specific rpm?
(add some more stiffness or mass?)
Thank you for quick reply.
RE: 3rd order+Noise
2) If it's a particular frequency/speed combination that's the problem (order cuts through resonance), the normal approach would be to tune something to absorb it. In the exhaust/intake world we add resonators (Helmholz & 1/4 wave).
RE: 3rd order+Noise
1) If your main order is 3rd order (i.e. if you have a 6-cylinder engine), this'll have a frequency of 60Hz at 1200 rev/min and 300 Hz at 6000 rev/min.
(a) What do you mean by if main order is 3rd order
My understanding is
If engine is running at 1200 rpm than (1200/60) so it would be 20 Hz why 60 hz?
So 2nd order 40 Hz (2400 rpm)
3rd order 60 Hz (3600 rpm)
4th order 80 Hz (4800 rpm)
5th order 100 Hz (6000 rpm)
2) Human is sensitive to near by 1kHz but engine is running max at 6000 rpm so only frequency is 100 hz than how come I plot upto 1000/1200 Hz?
May be the question won't be appropriate but will appreciate if you answer me
RE: 3rd order+Noise
RE: 3rd order+Noise
3rd Order
1200 rpm = 1200/60 x 3 = 60 hz
6000 rpm = 6000/60 x 3 = 300 hz
12th Order @ 6000 rpm
6000 rpm = 6000/60 x 12 = 1200 hz
etc.
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RE: 3rd order+Noise
Dave B
RE: 3rd order+Noise
Personally, I think that it was an oversimplified experiment and (as I remember) it ignored phase. Really the best way of doing this stuff is with a good binaural setup, such as that made by HEAD or B&K.
Cheers
Greg Locock
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RE: 3rd order+Noise
Do you recall the SAE paper number?
- Steve