GTR Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
344 Posts
Discussion Starter #1
Hi,

Anyone know where I can get my exhaust 'loudness' measured?

I'd like to get it checked before booking a track day and then possibly getting black flagged :chuckle:

Based in surrey. New setup has quad 4.5" ovals and despite 2 sets of resonators it's pretty damn loud (on a 300zx)
 

·
Registered
Joined
·
818 Posts
try a specialist hifi shop.. they tend to have sound meters knocking about.. if not maplin or cpc or RS do sound meters but youll be paying around £50 for one.
 

·
Registered
Joined
·
565 Posts
Jaffa,

Check out your local cruise website.

Up in Scotland each Cruise site and area has it's own Police Liaison Officer assigned.

We can go along to the Cop Shop for a free measurement and NO risk of prosecution as part of an awarness campaign.

Regards

ScotyB
 

·
Registered
Joined
·
23 Posts
iPhone dB meters

Yep iPhone has a number available but the best one I've tried is "SPL Meter" (you can calibrate it too). The only real limiting factor is the maximum limit of the built in mic ~120dB. How you translate the dB you measure to the typical drive-by standard at many circuits is a very black art due to sound wave interference from reflections. Whatever you measure will only ever be an approximation to on-track, full bore, max load situation but it'll give you a clue.

Just make sure you're as far from the mic down the straight as possible although this is not as good as it could be due to sound reflections but essentially every doubling of distance (source to mic)is a 4* reduction in volume (6dB) so for 110dB @ 1m from your exhaust in free-field (floating in the air)would become 104dB @2m and so on so for a 10m distance you would get ~ 90dB recorded. Again, you don't float you on a ground plane (the road) and any level would be above theoretical typically although the aforementioned interference patterns would render some frequencies loader and some less so.

Anyway, yes for about £1.50 you can get a darn good app, so if you've an iPhone great, or pay a mate to dl it from the app-store.

Good luck
Jen
 

·
Registered
Joined
·
344 Posts
Discussion Starter #6
right, for those interested, had a mate round with an iPhone today so downloaded the app and tried it.

97/98db at idle, approx 1 meter from exhaust.
blipping throttle to about 4k and hit 105db

oops :) will have to ensure the first track day has no limit and see what they measure it at!
 

·
Registered
Joined
·
838 Posts
Maplins are doing a sound level meter for less than £20.00. It measures in dBA which takes a broad spectrum of sound frequencies and so OK for your purpose. It is decent quality too. I work in audiology and purchased the same one from one of my suppliers about a year ago for £50.00 :confused:
Measured my R34 at 106 dB at tickover. No wonder the neighbours hate us! Got an Apexi bung now and much quieter, but haven't measured it yet.
Hope this helps.
 
1 - 8 of 8 Posts
Top