Sound Levels

good morning Dennis,

I'm up because of the damn cat! lol ... How about if I box him up & ship him to you?

It just so happens I own a sound level meter. I can check that for you later today. Do you want to know the sound level in the interior, or on the exterior? if exterior, is that from behind or ?

I'm going back to bed. Have a good day my friend.

George

George
I would love it if you could give
the sound levels from the back of the car!
Also if you know what the original specs were.
Can't believe the cat woke you up!
My car doesn't make any noise at night time,
it's also house trained.
Dennis

It should be louder in the front to clear the Emus and Kangaroos out of the way, no?

Thanks Doug
That's correct!
I am actually thinking of putting the mufflers at the front of the car...
I have heard New York has a vey big feral bear problem.
In your case it would make more sense to have it on the back of the car.
I have seen many National Geographic documentries and most bear attacks
happen from behind!
LOL
Dennis

OK Dennis, get ready for the nerdy stuff.

My car is a 100% stock 1974 Pantera L with about 70,000 miles on the odo.

I meaasured the car idling at 1000 rpm in a semi anechoic environment. 4 of the 6 planes surrounding the car were completely anechoic, 2 of the planes were very sound reflective (OK, the car was sitting in the driveway).

All measurements revealed exactly 20 db difference between the A weighted measurement and the C weighted measurement.

at 6 feet behnd the car the mneasurements were:

A weighting: 82 db
C weighting: 102 db

at 12 feet behind the car the measurements were:

A weighting: 79 db
C weighting: 99 db

your friend on the DTBB

George
Thank you very much!
You are such a great help, If I can be of any help to you, don't be hesitate to ask.
Especially if you need anything sourced from down here!
Your Mate Dennis

Anechoic? yips!

No, no, you misunderstand. It isn't a bear problem, it's a bare problem. (eat your heart out, heh, heh)

You rule Doug!

Gud day mite!

George
In Australia I have found out thata car must not exceed 96 Decibels at 3300rmp at 3metres!
Does that sound about right.
Dennis

Dennis,

Is that with or without an emu in the passenger seat?

My first question, is that an A weighted or a C weighted measurement. The spec for the noise limit should specify what type of measurement that is. Obviously, you have much more room to pass with an A weighted measurement.

It seems like a fair spec to me, a certain noise level, measured at a specified distance, at a specified rpm. 96 db would be very loud if it is A weighted. If it is C weighted, you are probably just barely legal.

Do they actually measure sound in OZ? Are the law officers, or some other governmemt agent, carrying around sound level meters and checking cars? Or is there an annual inspection you must pass?

Your friend on the DTBB

George
The police dont do sound checks, but if they think your car is to loud they can defect it!
Then you must go to the DMV I think you call it! We call it the RTA road and traffic authority.
Then they do a noise level check.
What is A weighted and C weighted mean.
Dennis

quote:

Originally posted by Downunder:
...What is A weighted and C weighted mean...

Dennis,

Filter networks are used in sound measuring devices to give the instrument a characteristic response (sensitivity) to sound levels at various frequencies.

The most widely used sound level filter is the A scale, which roughly corresponds to the inverse of the 40 dB (at 1 kHz) equal-loudness curve. I know this means nothing to you, lets just say that the sensitivity of an A weighted measurement is rolled off in the low and high frequencies in order to approximate the sensitivity of the human ear at various frequencies. The A weighting network rolls off the response of the instrument below 1000 hz and above about 10,000 hz. Using this filter, a sound level meter is thus less sensitive to very high and very low frequencies. Measurements made on this scale are expressed as dBA.

The filtering network of the C scale is practically linear over several octaves. The low frequency sensitivity is linear to 100 hz, and rolls off below that frequency. The high frequencies are linear to about 5000 hz, and gently roll off above that frequency. Measurements made with this filter are expressed as dBC. This measurement is used for calibration of equipment, and the measurment of sound level peaks.

Your friend on the DTBB

Thanks for that george!
You are a wealth of knowledge.
George can you get on the chat room, im there now.
Dennis

There are what, 10,000 people who live in Australia, 25,000,000 kangaroos and so many Emu's that they have spread to the US.
What's the big deal with making a little noise? Aussie's are always drinking beer and singing Walsing Matilda in thier Spando's on the beach with them silly hats. Is there a limit on how loud they can sing too?