What causes the "turbo spool" sound?

[BISHILVR]

The blades on the wheels actually "ring" as high speed air strikes them, this is obviously some of the "whine" that some turbo's make.

 

[marcmsj]

Da whistle go woooooo!!!!!

I actually put one of those on my car once just as a joke... i reved it and the thing just flew right now

damn 3 inch piping

 

[greyforestgst]

Ok here's my serious answer now:

The noise is caused by a number of forces, but it basically stems from the "torturing" of the air passing through. Initially, the air is violently broken up and chopped into segments as it enters the inlet duct, passes through the inlet and encounters the compressor blades. Much of the sound thus created is in a wide range of frequencies, but a single frequency is also heard. This is the familiar "whine" caused by the compressor blades chopping up the air. This sound is called "discrete" beccause it has an identifiable frequency and can be recognized in relation to other sounds.

the frequency of the sound you hear in hz is proportional to the rpm of the turbo. at extremely high turbo rpm (150,000 as previously mentioned), the frequency of the turbo's spool is higher than the human ear can process, so all you hear is the air being moved.

but simplified, yeah, the turbo spool noise is caused by the turbo spooling
any sort of centrifugal fan will make those sounds - jet engines are another example. you get an air-moving noise of scattered frequencies, and then the one identifiable (or "discrete" in the above post) frequency that is proportional to fan rpm.

 

[joosdawg]

so now then what makes ones spool louder? the bigger the turbine the louder the spool sound? great times, what i thought was kinda wierd is that my t-25 was alot louder spool sound then my 14b ever was, both on full hardpipes? why? -Ryan

 

[2GeNTSi]

so now then what makes ones spool louder? the bigger the turbine the louder the spool sound? great times, what i thought was kinda wierd is that my t-25 was alot louder spool sound then my 14b ever was, both on full hardpipes? why? -Ryan

Yeah I loved the way the T-25 sounded with all hard-piping except for the compressor outlet to the ic. Now with the 14B I have replaced the lower ic pipe and removed the silencer before the ic, it's much quieter though.

 

[joosdawg]

Yeah I loved the way the T-25 sounded with all hard-piping except for the compressor outlet to the ic. Now with the 14B I have replaced the lower ic pipe and removed the silencer before the ic, it's much quieter though.

if you didnt have a hard lower pipe on the t-25 then YOu missed out on the whole sound completly, seriously i thought it was loud with upper pipe but once i put that lower on there things got super loud spoolin action my 14b sounds like tiny spool with lots of air noise vs lots of spool but small air rush which makes sense and id much rather have the performance than the sound any day -Ryan

 

[1993eclipseGS]

Unbolt your downpipe from the o2 housing and take it for a ride forward and in reverse.. You can hear it in neutral ''the spooling sound'' it's VERY loud it's just a complete whistle like a supercharger. and when you let off the gas when you're driving it ''unspools'' it sounds really mean. I unbolted my exhaust just to remember how it sounded, It sounds exactly like a diesel. My friends said i don't have a 4cyl dsm i have a peterbuilt or a freightliner or something hahaha

 

[dthquazi1]

Bad weather stripping makes a spooling sound at higher speeds. Just cut a slit in yours, All the real "tuner's" are doing it now.

Just like all the real tuners are slicing the shit out of their bumpers to made un-necessary intercoolers fit?

 

[2GeNTSi]

^Harsh, anyways I wonder what it would've sounded like with lower piping on the T-25 as well...did it replace the silencer (black box) too? About the spooling sound through the exhaust, I wish I had that...too bad I have two resonators on my catback. My friends 1G GSX used to have a 3" turbo-back with no resonators, super-loud and you can hear it whistle a bit.

 

[94Jettameowpsst]

Here is an actual good question tho, idk about anyone else, but have you ever ran without an intake on your turbo and it makes your bov sound completely, i mean COMPLETELY different?? My tial w/ no intake on the turbo sounds like my old type s WTF